This document describes a study that retrofitted a residential refrigerator with a thermosyphon cooling system to utilize outdoor ambient temperatures for cooling. The thermosyphon uses phase change of a working fluid and natural convection to passively transfer heat from the refrigerator interior to the outdoors. Experimental results are presented on the refrigerator interior temperature, energy consumption, and cooling performance for different ambient temperatures, fan configurations, and thermosyphon design parameters. The system aims to reduce refrigerator energy use by leveraging cold outdoor conditions for cooling instead of using electricity.
The document compares the experimental performance of a thermoelectric refrigerator to a vapor compression refrigerator. It finds that for 325 ml of water cooled from 32°C to below 6°C:
- In the commercial refrigerator's freezer compartment, the water temperature decreased linearly with time, taking 61 minutes to reach 6°C.
- In the thermoelectric refrigerator, the water temperature decreased exponentially with time, taking 69 minutes to reach 6°C.
- For most of the cooling time, the thermoelectric refrigerator cooled at a faster rate than the commercial refrigerator.
This document discusses the design and analysis of an air-conditioned tricycle that uses thermoelectric cooling. The system uses multiple thermoelectric Peltier modules to absorb heat from the air and provide cooling. Rectangular fins and fiber sheets are used to improve heat transfer from the modules. The design is intended to provide cooling without using ozone-depleting refrigerants. Experimental results showed the thermoelectric system was able to achieve a cooling power of 50W per module with a coefficient of performance between 1.5-2. The document reviews several other studies on thermoelectric cooling systems and their advantages over traditional vapor-compression air conditioners.
This document summarizes a review of cooling tower performance and opportunities for energy savings through economizer operation. It discusses how cooling towers work and rejects heat to the atmosphere. It notes that cooling towers are a major energy user in buildings and manufacturing. The document then reviews the Merkel theory model for predicting cooling tower performance and its limitations, especially at low fan speeds and wet bulb temperatures. It proposes creating a new model to more accurately predict performance under these conditions to better assess energy savings opportunities like economizer operation.
To design any air-conditioning unit, estimation of heating or cooling load is very important. It helps us in design different devices most importantly the humidifier (in case of winter) or de-humidifier (in case of summer).
DESIGN AND FABRICATION OF THERMO ACOUSTIC REFRIGERATORP singh
In an age of impending energy and environmental crises, current cooling technologies continue to generate greenhouse gases with high energy costs. Thermo acoustic refrigeration is an innovative alternative for cooling that is both clean and inexpensive.
Thermo acoustic refrigerators are systems which use sound waves and a non-flammable mixture of inert gases to generate refrigeration effect. The main components are a closed cylinder, an acoustic driver, a porous component called a stack, and two heat-exchangers. Application of acoustic waves through the driver makes the gas resonant. As the gas oscillates back and forth, it creates a temperature difference along the length of the stack. This temperature change is due to compression and expansion of the gas by the sound pressure and the rest is a consequence of heat transfer between the gas and the stack. The temperature difference is used to remove heat from the cold side and reject it at the hot side of the system, producing cooling.
This document summarizes an experimental study on heat transfer and flow friction characteristics of a solar water heater with inserted baffles inside tubes. The study found that inserting full-length baffles inside tubes enhanced heat transfer and improved solar water heater performance compared to plain tubes. Maximum collector efficiency and outlet fluid temperature occurred at 12:45 hours for both baffled and plain tubes, but values were higher for baffled tubes. Friction factor was also lower for the baffled tube design at the point of maximum outlet temperature. The baffled tube design improved heat transfer and solar water heater performance relative to the plain tube design.
Design and Analysis of Fin-X Technology Nitish Sharma
The document analyzes Fin-X technology, which uses fins inspired by jet engine design to more efficiently transfer heat in cookware. It describes how fins draw on heat that would otherwise escape conventional pans and distribute it more evenly. Thermal analysis in ANSYS of standard and finned vessel models shows the finned vessel achieves 15% greater efficiency by transferring heat to its contents 15% faster than the standard vessel using the same input heat. The technology has potential to save household fuel or develop efficient cooking vessels for countries with energy scarcity issues.
This document summarizes the design, fabrication, and performance study of a solar air collector for room heating in Bangladesh. The collector was designed to be 1.23 square meters in size and heat a 1.365 cubic meter room. Data on inlet and outlet air temperatures were collected to calculate heat gain and collector efficiency. The maximum collector efficiency reached 32.79% when the inlet temperature was 35°C and outlet was 45°C. Graphs show efficiency and temperature differences over time on three days, with the maximum temperature difference reaching 10°C at 1:30PM and efficiency peaking then as well. The solar air collector provided effective room heating for 8 hours per day.
The document compares the experimental performance of a thermoelectric refrigerator to a vapor compression refrigerator. It finds that for 325 ml of water cooled from 32°C to below 6°C:
- In the commercial refrigerator's freezer compartment, the water temperature decreased linearly with time, taking 61 minutes to reach 6°C.
- In the thermoelectric refrigerator, the water temperature decreased exponentially with time, taking 69 minutes to reach 6°C.
- For most of the cooling time, the thermoelectric refrigerator cooled at a faster rate than the commercial refrigerator.
This document discusses the design and analysis of an air-conditioned tricycle that uses thermoelectric cooling. The system uses multiple thermoelectric Peltier modules to absorb heat from the air and provide cooling. Rectangular fins and fiber sheets are used to improve heat transfer from the modules. The design is intended to provide cooling without using ozone-depleting refrigerants. Experimental results showed the thermoelectric system was able to achieve a cooling power of 50W per module with a coefficient of performance between 1.5-2. The document reviews several other studies on thermoelectric cooling systems and their advantages over traditional vapor-compression air conditioners.
This document summarizes a review of cooling tower performance and opportunities for energy savings through economizer operation. It discusses how cooling towers work and rejects heat to the atmosphere. It notes that cooling towers are a major energy user in buildings and manufacturing. The document then reviews the Merkel theory model for predicting cooling tower performance and its limitations, especially at low fan speeds and wet bulb temperatures. It proposes creating a new model to more accurately predict performance under these conditions to better assess energy savings opportunities like economizer operation.
To design any air-conditioning unit, estimation of heating or cooling load is very important. It helps us in design different devices most importantly the humidifier (in case of winter) or de-humidifier (in case of summer).
DESIGN AND FABRICATION OF THERMO ACOUSTIC REFRIGERATORP singh
In an age of impending energy and environmental crises, current cooling technologies continue to generate greenhouse gases with high energy costs. Thermo acoustic refrigeration is an innovative alternative for cooling that is both clean and inexpensive.
Thermo acoustic refrigerators are systems which use sound waves and a non-flammable mixture of inert gases to generate refrigeration effect. The main components are a closed cylinder, an acoustic driver, a porous component called a stack, and two heat-exchangers. Application of acoustic waves through the driver makes the gas resonant. As the gas oscillates back and forth, it creates a temperature difference along the length of the stack. This temperature change is due to compression and expansion of the gas by the sound pressure and the rest is a consequence of heat transfer between the gas and the stack. The temperature difference is used to remove heat from the cold side and reject it at the hot side of the system, producing cooling.
This document summarizes an experimental study on heat transfer and flow friction characteristics of a solar water heater with inserted baffles inside tubes. The study found that inserting full-length baffles inside tubes enhanced heat transfer and improved solar water heater performance compared to plain tubes. Maximum collector efficiency and outlet fluid temperature occurred at 12:45 hours for both baffled and plain tubes, but values were higher for baffled tubes. Friction factor was also lower for the baffled tube design at the point of maximum outlet temperature. The baffled tube design improved heat transfer and solar water heater performance relative to the plain tube design.
Design and Analysis of Fin-X Technology Nitish Sharma
The document analyzes Fin-X technology, which uses fins inspired by jet engine design to more efficiently transfer heat in cookware. It describes how fins draw on heat that would otherwise escape conventional pans and distribute it more evenly. Thermal analysis in ANSYS of standard and finned vessel models shows the finned vessel achieves 15% greater efficiency by transferring heat to its contents 15% faster than the standard vessel using the same input heat. The technology has potential to save household fuel or develop efficient cooking vessels for countries with energy scarcity issues.
This document summarizes the design, fabrication, and performance study of a solar air collector for room heating in Bangladesh. The collector was designed to be 1.23 square meters in size and heat a 1.365 cubic meter room. Data on inlet and outlet air temperatures were collected to calculate heat gain and collector efficiency. The maximum collector efficiency reached 32.79% when the inlet temperature was 35°C and outlet was 45°C. Graphs show efficiency and temperature differences over time on three days, with the maximum temperature difference reaching 10°C at 1:30PM and efficiency peaking then as well. The solar air collector provided effective room heating for 8 hours per day.
microclimatic modeling and analysis of a fog cooled naturally ventilated gree...IJEAB
In the present paper, a thermal model has been presented for predicting the thermal environment inside a fog cooled naturally ventilated greenhouse. Experiments were conducted on a polyethylene covered greenhouse having 250 m2 ground area located at Coochbehar (latitude: 26.2o N, longitude: 89oE), West Bengal, India. The greenhouse was cooled by intermittent fogging with three distinct fogging cycles during the experiments. The greenhouse air temperature profiles as predicted by theoretical model were validated for different fogging cycle configurations. The model prediction and experimental results build up a good match (co-efficient of correlation was in range of 0.85 to 0.97). It was observed that fogging cycle configuration (spray time and spray interval combination) influences greatly the cooling performance of the fogging system. Further analysis revealed that greenhouse temperature could be maintained 2-5oC below the ambient temperature by employing suitable fogging cycle, maintaining the relative humidity within acceptable level.
ENERGY SAVINGS IN DOMESTIC REFRIGERATOR USING TWO THERMOELECTRIC MODULES& WAT...ijiert bestjournal
The study deals with hybrid refrigerator that combi nes thermoelectric (TER) and vapor compression refrigeration (VCR) and also entail exp erimental details of combined VCR & TER system. Objective is to configure hybrid refrig erator by introducing two Peltier modules (TER) in domestic refrigerator and to analyze compr essor cycles of conventional refrigerator with TER to increase energy efficiency of vapor com pression cycle. For this comparison of standalone VCR and Hybrid VCR+TER system is carried out. A Peltier module of size 4cm � 4cm � .4cm is introduced in the refrigerator cabinet & t he effect on energy efficiency in terms of trip time of compressor is recorded. The e ffect of Air cooled & Water cooled condenser with TER in different structures is also investigated. It is observed that by introducing thermoelectric effect,energy consumpti on of VCR is reduced by almost 10.92% annually,which accounts for 80 units per year. Thu s ultimately improving COP of the hybrid system with better control on temperature over the total run time.
PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEEDIAEME Publication
During summer use of khush curtains and water spraid over the khash (fibre) curtain for air cooling is done. But the determination of the extent of cooling is limited up to the wet bulb temperature in Conventional Cooler air is passes at uniform rate through wetted pad. In this process humidity increases sometimes which is not desirable. In Two Stage Air Cooler the primary air is cooled by a contact surface which is maintained at lower temperature air and water on the other side of the contact surface
After analysis it is found that in Two Stage Air Cooler Effective temperature decreases COP increases up to 13 which are significantly higher than normal cooler and conventional air conditioner.
Coefficient of Performance Enhancement of Refrigeration CyclesIJERA Editor
This document summarizes an experimental study that investigated enhancing the coefficient of performance (COP) of refrigeration cycles by using different condenser designs. Three condenser designs were tested in a refrigerator: the original design and two new designs (one with plain copper tubes and one with copper tubes welded to a stainless steel plate). Measurements of temperature, pressure, heat rejection, and COP were taken over time under varying evaporator loads. The results showed that the COP of the new designs increased by up to 20% compared to the original design when no load was applied. COP generally increased with higher evaporator loads. The plain copper tube design performed best, providing better heat transfer than the welded plate design.
An experimental investigation of annular fins under forced convectioneSAT Journals
Abstract
Heat transfer characteristics under forced convection are investigated experimentally by varying parameters like surface area,
base-to-ambient temperature difference and Reynolds number. To investigate the performance of fins experimentally, fins made of
aluminium (high thermal conductivity) are taken. For varying the surface area fin with 11 mm diameter without circumferential
fins, fin with 31 mm diameter and annular fins of 31 mm diameter are taken as specimens. Base to ambient temperature difference
is varied with the aid of dimmerstat ranging from 25W to 45W. Reynolds number is also varied by varying the velocities of air.
Velocities are varied by the aid of fan. Then these fins are tested under different load conditions, different Reynolds number by
varying the surface area of fins increase the rate of heat transfer. With the variation of relevant parameters under forced
convection heat transfer rates are analyzed experimentally. Experiments are conducted by using the annular fins, fin with
diameter 11mm without circumferential fins and fin with diameter 31mm at different Reynolds number and loads under forced
convection and comparison is made between fins. Experimental results shows that forced convection heat transfer rate from fins
depend on surface areas, base ambient temperature difference and Reynolds number. The base temperature for annular fins is
reduced by 30% when compared to fin with diameter 11mm due to increase in surface area about 40%. The base temperature for
annular fins is reduced by 10% when compared to fin with diameter of 31mm due to decrease in surface area about 41%. It is
also observed that at higher heat load i.e., 45W, the overall fin efficiency of annular fins is increased by 44% and 8% compared to
fin with diameter of 11mm and 31mm respectively. At higher Reynolds number range 800-2000, heat transfer rate increases in
annular fins due to more number of air molecules get in contact with the heated surface
This document discusses heat transfer through fins. It describes how fins are used to increase heat transfer from a surface by increasing surface area. Different types of fins are described, including straight, annular, and trapezoidal fins. The document discusses how fin performance is evaluated using effectiveness, efficiency, and overall surface efficiency. It presents results on the effects of flow rate on heat transfer, showing that heat transfer increases with increasing flow rate. The conclusion states that rectangular fins have the highest heat transfer but also the highest pressure drop, while plain fins have the lowest heat transfer but also the lowest pressure drop.
This document presents a theoretical analysis of the thermal and thermohydraulic performance of solar air heaters with finned absorber plates. Mathematical models are developed to analyze rectangular and triangular finned absorber plates. Effects of mass flow rate on parameters like collector efficiency factor, heat removal factor, temperature rise and efficiency are analyzed. The concept of effective efficiency is introduced to account for both thermal gain and pumping power losses. Results show that finned absorber plates can enhance thermal efficiency by up to 34% compared to flat plate absorbers. However, increased heat transfer also increases pressure drop, so optimization is needed to balance thermal and hydraulic performance.
IRJET- Optimization of Annular Fins by Modifying its Geometry with and Withou...IRJET Journal
This document reviews optimization of annular fins by modifying their geometry with and without perforations. It begins with an abstract discussing how fins dissipate heat and how their efficiency can be improved by increasing length, changing geometry, or adding more fins. It then discusses types of fins and their applications. The main body discusses how heat transfer occurs in fins and classifications of fins. It reviews literature on optimizing annular fin performance by varying materials, geometry, perforations, and other factors. The conclusion is that further optimization of annular fins is still possible in these and other ways. The future scope discusses analyzing perforated fins of different shapes and materials to further optimize efficiency and effectiveness.
This document summarizes a project seminar on analyzing extended surfaces subjected to forced convection. The project aims to increase heat transfer rates using different fin geometries. The objectives are to study heat transfer characteristics of various fin designs, fabricate a test rig, and analyze efficiency and effectiveness. The methodology includes theoretical calculations, analytical and experimental analysis, and comparing results. Future work may include different materials, fin shapes, and applications like electronics cooling. The experimental setup includes a fan, thermocouples, test fins, duct, and heater with dimmerstat control. Specifications of components are provided.
The document summarizes advances in solar air heaters. It describes the basic principles of solar air heaters and discusses two main types: low-cost single and double glazed heaters, and more efficient packed bed heaters. Experimental results showed the single glazed heater had higher efficiency in summer, while the double glazed was more efficient in winter. Roughness elements were also found to increase heat transfer and efficiency by inducing turbulence, with v-groove shapes working best. The document concludes roughness can significantly enhance solar air heater performance at a low cost.
it is basic introduction about Calculation of cooling load TETD due to sunlight & shaded roofs &walls using table,Load due to air filtration and Load due to ventilation.
Experimental and computational investigation of low cost standing wave thermo...IAEME Publication
This document presents experimental and computational investigation of a low-cost standing wave thermoacoustic refrigerator. Experimentally, a maximum temperature difference of 11K was obtained using a glass fiber stack with glass capillary tube spacers located at 0.15m from the speaker inlet. Computational fluid dynamics analysis using similar conditions obtained a temperature difference of 6K, in good agreement with experimental results. The study aims to develop an inexpensive standing wave thermoacoustic refrigerator design using readily available materials.
Three solar air heater having different absorber areas by er. vikas manushendraVikas Manushendra
In earlier years, the entire world has become completely dependent on relic energies such as natural gas, lubricant and coal. This type of resources are existing in limited amount. These resources has been created by natural processes across millions of years. The whole world is completely dependent upon energy. Energy is the basic part of our daily life. The utilization of energy in different purpose such as heating and cooling homes, schools and businesses. Energy is also used for lighting and appliances. In machinery purpose, energy perform different function such as running our vehicle, flying plane, boat sail and running machine. Energy is the player of new generation wealth and also it is significant component of economic development. In future consideration renewable energy is the main source of energy. The complete world is developing day by day and it requires more and more fuel so all the developing countries are focusing on shortage of fuels and necessity for other energy sources. Solar energy is the best alternative source of energy and also it is pollution free and unlimited energy. Nowadays world, the development of country is calculated by the energy utilization of country, the energy of utilization is completely connected with GDP of Country.
TFESC-12963_Said et al (Piezofan Project)John Bates
This document summarizes a study that investigated the effect of gap distance on heat transfer performance of a piezoelectric fan oriented parallel to a heated surface. Heat transfer coefficient maps were generated for gap distances of 1mm, 3mm, and 5mm. The 3mm gap produced the highest peak heat transfer coefficients and provided optimal cooling for most heater sizes tested. Analysis of centerline heat transfer profiles and optimization contours indicated that while a 1mm gap provided better coverage, the 3mm gap performed best overall and was the optimal configuration for most applications.
THERMAL PERFORMANCE AND ECONOMICS ANALYSIS OF DOUBLE FLOW PACKED BED SOLAR AI...IAEME Publication
Solar air heater is a type of heat exchanger that transforms solar radiation energy into heat energy. Conventional solar air heaters have poor thermal performance due to high heat losses and low convective heat transfer coefficient between absorber and flowing air. Attempts have been made to improve the thermal performance of conventional solar air heater by employing various design and flow arrangements. Double flow solar air heater with packing is an important and effective design improvement that has been proposed to improve the thermal performance. This paper presents the performance and economic analysis of double flow solar air collector with and without packing in the duct. Effect of various parameters on the thermal performance and pressure drop characteristics has been studied experimentally. The study concludes that double flow arrangement with packing is economical and having short payback period. Also, the thermal performance of double flow solar air heater with packing in upper duct is significantly higher compared to double flow solar air heater without packing and conventional solar air heater.
This document discusses cooling load estimation for a multi-story office building. It presents a thesis submitted for the degree of Master of Technology in Mechanical Engineering, with a focus on thermal engineering. The thesis analyzes cooling load calculation using the CLTD method for different climate conditions. It discusses factors that impact human comfort, and methods to calculate various internal and external heat gains that contribute to the total cooling load of a building. These include heat gains from occupants, lighting, equipment, infiltration, ventilation and through opaque and glass surfaces. The objective is to accurately size air conditioning equipment by determining the peak cooling load.
ARTICLE 58 IJAET VOLII ISSUE III JULY SEPT 2011Nirav Soni
The document reports on an experimental investigation of a double pass solar air heater with a corrugated absorber plate and Amul Cool aluminum cans. The study found that using a corrugated plate and aluminum cans in the double pass design increased the absorber plate temperature and thermal efficiency compared to a conventional single pass solar air heater. Tests were conducted to analyze how factors like time of day, solar insolation, and mass flow rate affected the absorber temperature and thermal efficiency of the modified solar air heater design.
This document discusses optimizing the design of a heat pump system using fuzzy logic and genetic algorithms. It first provides background on heat pumps and their operation. It then describes using fuzzy logic to determine thermodynamic properties of refrigerants, which are important for heat pump performance simulation and optimization. Next, it outlines using a genetic algorithm to optimize parameters of an air-source heat pump system with R-404a refrigerant. Fuzzy logic was employed to predict refrigerant properties for use in the genetic algorithm optimization of the heat pump system design. The approach showed potential for simplifying heat pump system optimization.
This document describes a study of a thermoacoustic refrigeration system. Thermoacoustic refrigeration uses sound waves to pump heat in a resonator tube, without ozone-depleting refrigerants. The study varied parameters like frequency, mean pressure, and cooling load to analyze their effects on the hot end temperature and temperature difference across the stack. Results showed that higher frequency, pressure, and cooling load increased hot end temperature, with an optimal pressure for maximum temperature difference. Compared to vapor compression systems, thermoacoustic refrigeration has fewer moving parts and lower maintenance costs while avoiding environmental hazards.
Thermo acoustic refrigeration is an innovative alternative for cooling that is both clean and inexpensive. The refrigeration effect is achieved by using sound waves and an inert gas which will not cause any damage to the atmosphere. Thermo acoustic engines and refrigerators were already being considered a few years ago for specialized applications. Their simplicity, lack of lubrication and sliding seals, and their use of environmentally harmless working fluids were adequate compensation for their lower efficiencies.
This document discusses a case study analyzing the life cycle of a multi-split Variable Refrigerant Flow (VRF) HVAC system installed in a building located in A.M.U. Aligarh, India. The building has a total area of 18,327 square feet split between the ground and first floors. The total cooling load was calculated to be 149.5 tons. Electricity consumption and costs were compared between the VRF system and conventional split systems over 10 and 12 year lifecycles. It was found that the VRF system consumed 330,000 units of electricity per year compared to 422,500 units for split systems, resulting in lower operating costs over the lifetime of the equipment.
microclimatic modeling and analysis of a fog cooled naturally ventilated gree...IJEAB
In the present paper, a thermal model has been presented for predicting the thermal environment inside a fog cooled naturally ventilated greenhouse. Experiments were conducted on a polyethylene covered greenhouse having 250 m2 ground area located at Coochbehar (latitude: 26.2o N, longitude: 89oE), West Bengal, India. The greenhouse was cooled by intermittent fogging with three distinct fogging cycles during the experiments. The greenhouse air temperature profiles as predicted by theoretical model were validated for different fogging cycle configurations. The model prediction and experimental results build up a good match (co-efficient of correlation was in range of 0.85 to 0.97). It was observed that fogging cycle configuration (spray time and spray interval combination) influences greatly the cooling performance of the fogging system. Further analysis revealed that greenhouse temperature could be maintained 2-5oC below the ambient temperature by employing suitable fogging cycle, maintaining the relative humidity within acceptable level.
ENERGY SAVINGS IN DOMESTIC REFRIGERATOR USING TWO THERMOELECTRIC MODULES& WAT...ijiert bestjournal
The study deals with hybrid refrigerator that combi nes thermoelectric (TER) and vapor compression refrigeration (VCR) and also entail exp erimental details of combined VCR & TER system. Objective is to configure hybrid refrig erator by introducing two Peltier modules (TER) in domestic refrigerator and to analyze compr essor cycles of conventional refrigerator with TER to increase energy efficiency of vapor com pression cycle. For this comparison of standalone VCR and Hybrid VCR+TER system is carried out. A Peltier module of size 4cm � 4cm � .4cm is introduced in the refrigerator cabinet & t he effect on energy efficiency in terms of trip time of compressor is recorded. The e ffect of Air cooled & Water cooled condenser with TER in different structures is also investigated. It is observed that by introducing thermoelectric effect,energy consumpti on of VCR is reduced by almost 10.92% annually,which accounts for 80 units per year. Thu s ultimately improving COP of the hybrid system with better control on temperature over the total run time.
PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEEDIAEME Publication
During summer use of khush curtains and water spraid over the khash (fibre) curtain for air cooling is done. But the determination of the extent of cooling is limited up to the wet bulb temperature in Conventional Cooler air is passes at uniform rate through wetted pad. In this process humidity increases sometimes which is not desirable. In Two Stage Air Cooler the primary air is cooled by a contact surface which is maintained at lower temperature air and water on the other side of the contact surface
After analysis it is found that in Two Stage Air Cooler Effective temperature decreases COP increases up to 13 which are significantly higher than normal cooler and conventional air conditioner.
Coefficient of Performance Enhancement of Refrigeration CyclesIJERA Editor
This document summarizes an experimental study that investigated enhancing the coefficient of performance (COP) of refrigeration cycles by using different condenser designs. Three condenser designs were tested in a refrigerator: the original design and two new designs (one with plain copper tubes and one with copper tubes welded to a stainless steel plate). Measurements of temperature, pressure, heat rejection, and COP were taken over time under varying evaporator loads. The results showed that the COP of the new designs increased by up to 20% compared to the original design when no load was applied. COP generally increased with higher evaporator loads. The plain copper tube design performed best, providing better heat transfer than the welded plate design.
An experimental investigation of annular fins under forced convectioneSAT Journals
Abstract
Heat transfer characteristics under forced convection are investigated experimentally by varying parameters like surface area,
base-to-ambient temperature difference and Reynolds number. To investigate the performance of fins experimentally, fins made of
aluminium (high thermal conductivity) are taken. For varying the surface area fin with 11 mm diameter without circumferential
fins, fin with 31 mm diameter and annular fins of 31 mm diameter are taken as specimens. Base to ambient temperature difference
is varied with the aid of dimmerstat ranging from 25W to 45W. Reynolds number is also varied by varying the velocities of air.
Velocities are varied by the aid of fan. Then these fins are tested under different load conditions, different Reynolds number by
varying the surface area of fins increase the rate of heat transfer. With the variation of relevant parameters under forced
convection heat transfer rates are analyzed experimentally. Experiments are conducted by using the annular fins, fin with
diameter 11mm without circumferential fins and fin with diameter 31mm at different Reynolds number and loads under forced
convection and comparison is made between fins. Experimental results shows that forced convection heat transfer rate from fins
depend on surface areas, base ambient temperature difference and Reynolds number. The base temperature for annular fins is
reduced by 30% when compared to fin with diameter 11mm due to increase in surface area about 40%. The base temperature for
annular fins is reduced by 10% when compared to fin with diameter of 31mm due to decrease in surface area about 41%. It is
also observed that at higher heat load i.e., 45W, the overall fin efficiency of annular fins is increased by 44% and 8% compared to
fin with diameter of 11mm and 31mm respectively. At higher Reynolds number range 800-2000, heat transfer rate increases in
annular fins due to more number of air molecules get in contact with the heated surface
This document discusses heat transfer through fins. It describes how fins are used to increase heat transfer from a surface by increasing surface area. Different types of fins are described, including straight, annular, and trapezoidal fins. The document discusses how fin performance is evaluated using effectiveness, efficiency, and overall surface efficiency. It presents results on the effects of flow rate on heat transfer, showing that heat transfer increases with increasing flow rate. The conclusion states that rectangular fins have the highest heat transfer but also the highest pressure drop, while plain fins have the lowest heat transfer but also the lowest pressure drop.
This document presents a theoretical analysis of the thermal and thermohydraulic performance of solar air heaters with finned absorber plates. Mathematical models are developed to analyze rectangular and triangular finned absorber plates. Effects of mass flow rate on parameters like collector efficiency factor, heat removal factor, temperature rise and efficiency are analyzed. The concept of effective efficiency is introduced to account for both thermal gain and pumping power losses. Results show that finned absorber plates can enhance thermal efficiency by up to 34% compared to flat plate absorbers. However, increased heat transfer also increases pressure drop, so optimization is needed to balance thermal and hydraulic performance.
IRJET- Optimization of Annular Fins by Modifying its Geometry with and Withou...IRJET Journal
This document reviews optimization of annular fins by modifying their geometry with and without perforations. It begins with an abstract discussing how fins dissipate heat and how their efficiency can be improved by increasing length, changing geometry, or adding more fins. It then discusses types of fins and their applications. The main body discusses how heat transfer occurs in fins and classifications of fins. It reviews literature on optimizing annular fin performance by varying materials, geometry, perforations, and other factors. The conclusion is that further optimization of annular fins is still possible in these and other ways. The future scope discusses analyzing perforated fins of different shapes and materials to further optimize efficiency and effectiveness.
This document summarizes a project seminar on analyzing extended surfaces subjected to forced convection. The project aims to increase heat transfer rates using different fin geometries. The objectives are to study heat transfer characteristics of various fin designs, fabricate a test rig, and analyze efficiency and effectiveness. The methodology includes theoretical calculations, analytical and experimental analysis, and comparing results. Future work may include different materials, fin shapes, and applications like electronics cooling. The experimental setup includes a fan, thermocouples, test fins, duct, and heater with dimmerstat control. Specifications of components are provided.
The document summarizes advances in solar air heaters. It describes the basic principles of solar air heaters and discusses two main types: low-cost single and double glazed heaters, and more efficient packed bed heaters. Experimental results showed the single glazed heater had higher efficiency in summer, while the double glazed was more efficient in winter. Roughness elements were also found to increase heat transfer and efficiency by inducing turbulence, with v-groove shapes working best. The document concludes roughness can significantly enhance solar air heater performance at a low cost.
it is basic introduction about Calculation of cooling load TETD due to sunlight & shaded roofs &walls using table,Load due to air filtration and Load due to ventilation.
Experimental and computational investigation of low cost standing wave thermo...IAEME Publication
This document presents experimental and computational investigation of a low-cost standing wave thermoacoustic refrigerator. Experimentally, a maximum temperature difference of 11K was obtained using a glass fiber stack with glass capillary tube spacers located at 0.15m from the speaker inlet. Computational fluid dynamics analysis using similar conditions obtained a temperature difference of 6K, in good agreement with experimental results. The study aims to develop an inexpensive standing wave thermoacoustic refrigerator design using readily available materials.
Three solar air heater having different absorber areas by er. vikas manushendraVikas Manushendra
In earlier years, the entire world has become completely dependent on relic energies such as natural gas, lubricant and coal. This type of resources are existing in limited amount. These resources has been created by natural processes across millions of years. The whole world is completely dependent upon energy. Energy is the basic part of our daily life. The utilization of energy in different purpose such as heating and cooling homes, schools and businesses. Energy is also used for lighting and appliances. In machinery purpose, energy perform different function such as running our vehicle, flying plane, boat sail and running machine. Energy is the player of new generation wealth and also it is significant component of economic development. In future consideration renewable energy is the main source of energy. The complete world is developing day by day and it requires more and more fuel so all the developing countries are focusing on shortage of fuels and necessity for other energy sources. Solar energy is the best alternative source of energy and also it is pollution free and unlimited energy. Nowadays world, the development of country is calculated by the energy utilization of country, the energy of utilization is completely connected with GDP of Country.
TFESC-12963_Said et al (Piezofan Project)John Bates
This document summarizes a study that investigated the effect of gap distance on heat transfer performance of a piezoelectric fan oriented parallel to a heated surface. Heat transfer coefficient maps were generated for gap distances of 1mm, 3mm, and 5mm. The 3mm gap produced the highest peak heat transfer coefficients and provided optimal cooling for most heater sizes tested. Analysis of centerline heat transfer profiles and optimization contours indicated that while a 1mm gap provided better coverage, the 3mm gap performed best overall and was the optimal configuration for most applications.
THERMAL PERFORMANCE AND ECONOMICS ANALYSIS OF DOUBLE FLOW PACKED BED SOLAR AI...IAEME Publication
Solar air heater is a type of heat exchanger that transforms solar radiation energy into heat energy. Conventional solar air heaters have poor thermal performance due to high heat losses and low convective heat transfer coefficient between absorber and flowing air. Attempts have been made to improve the thermal performance of conventional solar air heater by employing various design and flow arrangements. Double flow solar air heater with packing is an important and effective design improvement that has been proposed to improve the thermal performance. This paper presents the performance and economic analysis of double flow solar air collector with and without packing in the duct. Effect of various parameters on the thermal performance and pressure drop characteristics has been studied experimentally. The study concludes that double flow arrangement with packing is economical and having short payback period. Also, the thermal performance of double flow solar air heater with packing in upper duct is significantly higher compared to double flow solar air heater without packing and conventional solar air heater.
This document discusses cooling load estimation for a multi-story office building. It presents a thesis submitted for the degree of Master of Technology in Mechanical Engineering, with a focus on thermal engineering. The thesis analyzes cooling load calculation using the CLTD method for different climate conditions. It discusses factors that impact human comfort, and methods to calculate various internal and external heat gains that contribute to the total cooling load of a building. These include heat gains from occupants, lighting, equipment, infiltration, ventilation and through opaque and glass surfaces. The objective is to accurately size air conditioning equipment by determining the peak cooling load.
ARTICLE 58 IJAET VOLII ISSUE III JULY SEPT 2011Nirav Soni
The document reports on an experimental investigation of a double pass solar air heater with a corrugated absorber plate and Amul Cool aluminum cans. The study found that using a corrugated plate and aluminum cans in the double pass design increased the absorber plate temperature and thermal efficiency compared to a conventional single pass solar air heater. Tests were conducted to analyze how factors like time of day, solar insolation, and mass flow rate affected the absorber temperature and thermal efficiency of the modified solar air heater design.
This document discusses optimizing the design of a heat pump system using fuzzy logic and genetic algorithms. It first provides background on heat pumps and their operation. It then describes using fuzzy logic to determine thermodynamic properties of refrigerants, which are important for heat pump performance simulation and optimization. Next, it outlines using a genetic algorithm to optimize parameters of an air-source heat pump system with R-404a refrigerant. Fuzzy logic was employed to predict refrigerant properties for use in the genetic algorithm optimization of the heat pump system design. The approach showed potential for simplifying heat pump system optimization.
This document describes a study of a thermoacoustic refrigeration system. Thermoacoustic refrigeration uses sound waves to pump heat in a resonator tube, without ozone-depleting refrigerants. The study varied parameters like frequency, mean pressure, and cooling load to analyze their effects on the hot end temperature and temperature difference across the stack. Results showed that higher frequency, pressure, and cooling load increased hot end temperature, with an optimal pressure for maximum temperature difference. Compared to vapor compression systems, thermoacoustic refrigeration has fewer moving parts and lower maintenance costs while avoiding environmental hazards.
Thermo acoustic refrigeration is an innovative alternative for cooling that is both clean and inexpensive. The refrigeration effect is achieved by using sound waves and an inert gas which will not cause any damage to the atmosphere. Thermo acoustic engines and refrigerators were already being considered a few years ago for specialized applications. Their simplicity, lack of lubrication and sliding seals, and their use of environmentally harmless working fluids were adequate compensation for their lower efficiencies.
This document discusses a case study analyzing the life cycle of a multi-split Variable Refrigerant Flow (VRF) HVAC system installed in a building located in A.M.U. Aligarh, India. The building has a total area of 18,327 square feet split between the ground and first floors. The total cooling load was calculated to be 149.5 tons. Electricity consumption and costs were compared between the VRF system and conventional split systems over 10 and 12 year lifecycles. It was found that the VRF system consumed 330,000 units of electricity per year compared to 422,500 units for split systems, resulting in lower operating costs over the lifetime of the equipment.
IRJET- Design and Fabrication of Thermo Acoustic RefrigeratorIRJET Journal
This document describes the design and fabrication of a thermoacoustic refrigerator. Some key points:
1. Thermoacoustic refrigeration uses sound waves to alternately compress and relax gas particles in a tube, transferring heat without moving parts.
2. The refrigerator consists of a resonator tube containing a stack of closely spaced surfaces through which a sound wave oscillates. Heat is transferred between the gas and stack surfaces.
3. Experiments investigated different stack geometries and materials to optimize heat transfer and the refrigerator's performance. Temperature sensors measured the temperature difference created.
Waste Heat Recovery From Refrigeration PlantIRJET Journal
This document summarizes waste heat recovery from a refrigeration plant condenser. It discusses how the waste heat from a condenser, which is currently released into the environment, can instead be captured and used for applications like water heating. The document then provides technical details on heat transfer methods, refrigerants, and vapor compression refrigeration systems. It analyzes using the condenser waste heat from a 30-ton refrigeration plant to heat water up to 50°C, which could then be used for low-temperature household or industrial purposes. Capturing this waste heat improves overall system efficiency and reduces environmental impacts.
DIRECT EXPANSION GROUND SOURCE HEAT PUMPS FOR HEATING AND COOLINGIJSIT Editor
This article is an introduction to the energy problem and the possible saving that can be achieved
through improving building performance and the use of ground energy sources. The relevance and
importance of the study is discussed in the paper, which, also, highlights the objectives of the study, and the
scope of the theme. This study discusses some of the current activity in the GSHPs field. The basic system and
several variations for buildings are presented along with examples of systems in operation. Finally, the GCHP
is presented as an alternative that is able to counter much of the criticism leveled by the natural gas industry
toward conventional heat pumps. Several advantages and disadvantages are listed. Operating and installation
costs are briefly discussed.
Cold Storage Room Design. How you can do that? How you can learn that? Product heat load, infiltration heat load, internal heat load, refrigeration equipment heat load, transportation of refrigerated foods, safety factor, thermal conductivity,
This report analyzes the design of a hybrid cooling system consisting of both wet and dry sections. Key findings include:
1) The wet section requires 36 cells based on a water flow rate of 155,000 t/h. Each cell requires an air flow rate of 443 kg/s.
2) The dry section requires 72 cells based on a water flow rate of 598 kg/s per cell.
3) Analyzing the systems using NTU effectiveness, a series configuration with the dry section first is more efficient, allowing more heat removal by the dry section and reducing water consumption in the wet section.
4) Operation modes are identified, with a maximum water conservation mode handling 73% of
IRJET- A Review on Thermal Analysis and Optimization of Heat Exchanger Design...IRJET Journal
This document discusses heat exchangers and their optimization for co-generation units. It begins with an abstract discussing heat exchangers and their uses. It then discusses key factors that influence heat exchanger efficiency such as temperature differential, flow rate, and installation configuration. Common heat exchanger materials are also discussed. The document then focuses on co-generation and discusses past studies on optimizing heat exchangers for co-generation units through variables like number of tubes, tube diameter, and inlet velocity. The present work aims to obtain the best heat exchanger design for co-generation units by comparing efficiency under different parameters.
An overview of stack design for a thermoacoustic refrigeratoreSAT Journals
Abstract A thermoacoustic refrigerator utilizes the thermal interactions of the sound waves with the medium while they travel to produce refrigeration. Sound energy propagates in longitudinal fashion through the medium, thus resulting in compressions and rarefactions in the medium and hence heating and cooling the medium subsequently. The stack acts as a medium to transfer the heat from one point in the system to another. The stack is thus the heart of any thermoacoustic refrigeration system. This paper provides a brief overview of the construction and working of the thermoacoustic refrigerator and focusses on the stack of a thermoacoustic refrigeration system. The desired thermal properties of the stack material like the thermal conductivity and specific heat have been discussed. An optimum spacing obtained from previous works based on the thermal and viscous penetration depths has been briefly discussed. Various stack geometries like the parallel plate type, the spiral type, pin type and porous stacks made of reticulated vitreous carbon have been elaborated. Keywords: Thermoacoustic refrigerator, Stack, Thermal penetration depth, Stack geometry, Stack spacing.
Heat Transfer Enhancement of Plate Fin Heat Sinks – A Reviewijtsrd
Heat sinks have been commonly used for cool electrical, electronic and automotive parts in many industrial applications. They are effective in extracting heat at high temperatures from surfaces. The reliability of such systems depends on the temperature of their operation. Heat sinks are important components of most of these devices thermal management systems, such as diodes, thyristor, high power semiconductor devices such as integrated inverter circuits, audio amplifiers, microprocessors or microcontrollers. This paper highlights the use of heat sinks in electronic cooling applications, and discusses relevant literature to enhance the heat transfer efficiency of plate fin heat sinks by modifying the surface, interrupting the boundary layer and shifting the path. Prof. Pushparaj Singh | Prashant Kumar Pandey "Heat Transfer Enhancement of Plate Fin Heat Sinks – A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33374.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33374/heat-transfer-enhancement-of-plate-fin-heat-sinks-–-a-review/prof-pushparaj-singh
IRJET- Comparative Study of Domestic Refrigerator by using Parallel Coil and ...IRJET Journal
This document presents a comparative study of domestic refrigerators using parallel coil and helical coil condensers. It discusses how helical coils provide advantages over parallel coils, including being more compact, providing higher heat transfer coefficients, and allowing for more effective pressure drop. The increased heat transfer of a helical coil condenser allows for increased COP and decreased power requirements for the compressor compared to a parallel coil condenser. The document provides background on refrigeration systems, defines helical coils and discusses how their curved shape induces secondary flow and higher heat transfer. It also reviews previous literature on refrigeration system performance and design.
1. The document discusses an Earth Tube Heat Exchanger system that uses geothermal energy for heating and cooling buildings. It can draw heat from the ground to warm a building in winter and release heat into the ground to cool a building in summer.
2. The system was analyzed using theoretical calculations and CFD simulations in ANSYS Fluent software. Key parameters like pipe diameter and air velocity were varied to analyze their effects on the system's coefficient of performance.
3. Modifying parameters like increasing pipe diameter and air velocity were found to have the most significant impact on improving the system's coefficient of performance. The Earth Tube Heat Exchanger provides an efficient alternative to conventional HVAC systems by making use of
Raji Panicker presents simplified design equations for earth-air heat exchangers (EAHEs) that can be implemented through a spreadsheet. The equations allow calculation of undistributed ground temperature throughout the year, the length of tube required for desired heat transfer effectiveness, and the pressure drop and exit air temperature. The equations make assumptions about constant ground temperature and properties. An example application to Bangalore, India is provided and validated with computational fluid dynamics simulations.
IRJET- Critical Analysis of Thermoelectric Cycle (Tri-Cycle)IRJET Journal
1) The document describes the critical analysis of a thermoelectric air conditioning system called a tri-cycle that can provide comfortable transport and delivery of goods.
2) It uses thermoelectric modules instead of harmful refrigerants like ammonia or CFCs that pollute the atmosphere and damage the ozone layer.
3) The thermoelectric air conditioning system has advantages over conventional systems like being compact, lightweight, having no moving parts so it does not wear out or leak refrigerants.
1) The document discusses the study and fabrication of a thermoelectric air cooling and heating system as an alternative to conventional HVAC systems that use harmful refrigerants.
2) A thermoelectric module uses the Peltier effect to create a temperature difference between its two ceramic plates when a current is passed through it. Multiple thermocouples connected in series allow one plate to be heated and the other cooled.
3) The methodology discusses considerations for designing a thermoelectric cooling system such as the temperatures involved, heat load, cooling time, ambient conditions, and available space for the module and heat sink.
In present scenario, HVAC system (commonly used in the air conditioners) is very efficient and reliable but it has some demerits. It has been observed during the last two decades that the O3 layer is slowly destroyed because of the refrigerant (CFC and HFC) used for the refrigeration and air- conditioning purposes. The common refrigerant used is HFC's which are leaked and slowly ascend into the atmosphere. When they reach to O3 layer they act on O3 molecules and the layer of O3 is destroyed. A single molecule of HFC can destroy thousands of O3 molecules and that's why it has created a threat for the not only to maintain earth eco system stable but also to existence of earth. Even the percentage of HFCs are emitted into the atmosphere compared to CO2 is negligible but its global warming effect is few thousand times of CO2. The effect of 100 gm of HFC can destroy 0.5 tons of O3 molecules. These HFCs once destroy O3 layer; it takes hundreds of years to recover its thickness as it is formed by complex reactions. This is because as HFCs comes in environment, they remain in atmosphere for 18 years. The capacity of HFCs to increase in earth temperature 10% is contributed by HFC's only. That leads to the emergence of finding an alternative of the conventional HVAC system, i.e. thermo-electric cooling and heating system.
EXPERIMENTAL INVESTIGATION OF WASTE HEAT RECOVERY SYSTEM FOR DOMESTIC REFRIGE...IAEME Publication
The document describes an experimental investigation of waste heat recovery from a domestic refrigerator. The refrigerator's condenser was immersed in a water tank to recover heat through desuperheating of the refrigerant gas. Testing was conducted with and without a water load under no-load and full-load refrigerator conditions. Outlet water temperature increased over time for all tests, reaching over 40°C within 30 minutes. Power consumption decreased as outlet water temperature increased. The coefficient of performance also decreased over time as the system approached steady state conditions. The results indicate waste heat recovery from domestic refrigerators is technically feasible and economically viable.
The document describes the design and setup of a thermoacoustic refrigeration system as an environmentally friendly alternative to vapor compression refrigeration. Key components include an acoustic driver, stack, working fluid, and acoustic resonator. The driver converts electrical power to acoustic waves in the resonator tube filled with working fluid. A spiral stack within the tube facilitates heat pumping via the thermoacoustic effect as gas parcels compress and expand. The system aims to demonstrate cooling without ozone-depleting refrigerants through analyzing and testing a prototype.
Similar to Thermosyphon assisted cooling-system_for_refrigera (20)
Gas agency management system project report.pdfKamal Acharya
The project entitled "Gas Agency" is done to make the manual process easier by making it a computerized system for billing and maintaining stock. The Gas Agencies get the order request through phone calls or by personal from their customers and deliver the gas cylinders to their address based on their demand and previous delivery date. This process is made computerized and the customer's name, address and stock details are stored in a database. Based on this the billing for a customer is made simple and easier, since a customer order for gas can be accepted only after completing a certain period from the previous delivery. This can be calculated and billed easily through this. There are two types of delivery like domestic purpose use delivery and commercial purpose use delivery. The bill rate and capacity differs for both. This can be easily maintained and charged accordingly.
Software Engineering and Project Management - Software Testing + Agile Method...Prakhyath Rai
Software Testing: A Strategic Approach to Software Testing, Strategic Issues, Test Strategies for Conventional Software, Test Strategies for Object -Oriented Software, Validation Testing, System Testing, The Art of Debugging.
Agile Methodology: Before Agile – Waterfall, Agile Development.
Applications of artificial Intelligence in Mechanical Engineering.pdfAtif Razi
Historically, mechanical engineering has relied heavily on human expertise and empirical methods to solve complex problems. With the introduction of computer-aided design (CAD) and finite element analysis (FEA), the field took its first steps towards digitization. These tools allowed engineers to simulate and analyze mechanical systems with greater accuracy and efficiency. However, the sheer volume of data generated by modern engineering systems and the increasing complexity of these systems have necessitated more advanced analytical tools, paving the way for AI.
AI offers the capability to process vast amounts of data, identify patterns, and make predictions with a level of speed and accuracy unattainable by traditional methods. This has profound implications for mechanical engineering, enabling more efficient design processes, predictive maintenance strategies, and optimized manufacturing operations. AI-driven tools can learn from historical data, adapt to new information, and continuously improve their performance, making them invaluable in tackling the multifaceted challenges of modern mechanical engineering.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Discover the latest insights on Data Driven Maintenance with our comprehensive webinar presentation. Learn about traditional maintenance challenges, the right approach to utilizing data, and the benefits of adopting a Data Driven Maintenance strategy. Explore real-world examples, industry best practices, and innovative solutions like FMECA and the D3M model. This presentation, led by expert Jules Oudmans, is essential for asset owners looking to optimize their maintenance processes and leverage digital technologies for improved efficiency and performance. Download now to stay ahead in the evolving maintenance landscape.
AI for Legal Research with applications, toolsmahaffeycheryld
AI applications in legal research include rapid document analysis, case law review, and statute interpretation. AI-powered tools can sift through vast legal databases to find relevant precedents and citations, enhancing research accuracy and speed. They assist in legal writing by drafting and proofreading documents. Predictive analytics help foresee case outcomes based on historical data, aiding in strategic decision-making. AI also automates routine tasks like contract review and due diligence, freeing up lawyers to focus on complex legal issues. These applications make legal research more efficient, cost-effective, and accessible.
Generative AI Use cases applications solutions and implementation.pdfmahaffeycheryld
Generative AI solutions encompass a range of capabilities from content creation to complex problem-solving across industries. Implementing generative AI involves identifying specific business needs, developing tailored AI models using techniques like GANs and VAEs, and integrating these models into existing workflows. Data quality and continuous model refinement are crucial for effective implementation. Businesses must also consider ethical implications and ensure transparency in AI decision-making. Generative AI's implementation aims to enhance efficiency, creativity, and innovation by leveraging autonomous generation and sophisticated learning algorithms to meet diverse business challenges.
https://www.leewayhertz.com/generative-ai-use-cases-and-applications/
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELijaia
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
Use PyCharm for remote debugging of WSL on a Windo cf5c162d672e4e58b4dde5d797...shadow0702a
This document serves as a comprehensive step-by-step guide on how to effectively use PyCharm for remote debugging of the Windows Subsystem for Linux (WSL) on a local Windows machine. It meticulously outlines several critical steps in the process, starting with the crucial task of enabling permissions, followed by the installation and configuration of WSL.
The guide then proceeds to explain how to set up the SSH service within the WSL environment, an integral part of the process. Alongside this, it also provides detailed instructions on how to modify the inbound rules of the Windows firewall to facilitate the process, ensuring that there are no connectivity issues that could potentially hinder the debugging process.
The document further emphasizes on the importance of checking the connection between the Windows and WSL environments, providing instructions on how to ensure that the connection is optimal and ready for remote debugging.
It also offers an in-depth guide on how to configure the WSL interpreter and files within the PyCharm environment. This is essential for ensuring that the debugging process is set up correctly and that the program can be run effectively within the WSL terminal.
Additionally, the document provides guidance on how to set up breakpoints for debugging, a fundamental aspect of the debugging process which allows the developer to stop the execution of their code at certain points and inspect their program at those stages.
Finally, the document concludes by providing a link to a reference blog. This blog offers additional information and guidance on configuring the remote Python interpreter in PyCharm, providing the reader with a well-rounded understanding of the process.
3. refrigeration applications, the refrigerator resides in an envi-
ronment maintained near 20–24 °C, and uses electricity to move
heat from the refrigerated space at a temperature of 2–5 °C to
the environment. In many parts of the U.S., however, the outside
temperature falls below the refrigerated space temperature
for several months out of the year, particularly in the north-
ern portions of the country. A natural choice then is to use the
low outside temperatures during the cold season for cooling
to reduce electricity usage for residential refrigerators.
One method to utilize low outside temperatures for near-
zero-cost refrigeration is to place a two-phase thermosyphon
inside of the refrigerated space, then to extend the top of the
thermosyphon though the building envelope vertically or
through a wall to the outside (Fig. 1).
The two-phase thermosyphon has several key features
that make it well-suited for residential and commercial re-
frigeration applications. Because it uses the latent heat of phase
change, the temperature difference required to move heat
through the thermosyphon is very small. Thermosyphons
are closely related to heat pipes, which are used extensively
for cooling in electronic and computer equipment, high-
performance heat exchangers, and satellites (Dunn and Reay,
2012; Faghri, 1995). Unlike a heat pipe, however, heat flow only
occurs if the temperature in the bottom section of the
thermosyphon is greater than the temperature at the top
because gravity maintains the liquid required for the phase
change process in the bottom of the device only. In this sense,
the device acts like a thermal diode or check valve, and will
automatically shut-off when the ambient temperature exceeds
the refrigerated space temperature.
The thermosyphon operation is completely passive, with
no pump needed since phase change and gravity alone drive
the heat transfer process. There are no moving parts and the
device is permanently sealed at the time of manufacture. The
device is inexpensive and can be made using a variety of ma-
terials and working fluids best suited for the application.
The low thermal resistance provided by the thermosyphon
is important so that it can provide the required cooling with
as warm an ambient temperature as possible. The relation-
ship between heat flow, temperature difference, and thermal
resistance through the thermosyphon is
Q T T Rr r th= −( )∞ (1)
Here Qr represents the steady-state heat removal rate re-
quired to maintain the refrigerated space at the desired
temperature, Tr.The ambient temperature is T∞ and ΔT = Tr − T∞
is the temperature difference between the refrigerated space
and the ambient temperature. For a residential refrigerator, the
average Qr is ~40–50 W (U.S. Environmental Protection Agency
and U.S. Department of Energy, 2016), and varies with the size
of the refrigerator, the temperature set point (Tr), effectiveness
Nomenclature
Cp specific heat capacity [J kg−1
K−1
]
hfg latent heat of vaporization [J kg−1
]
k thermal conductivity [W m−1
K−1
]
L length [m]
m mass of water used for thermal load [kg]
P electrical power [W]
Q total heat transfer [J]
Qr heat removal rate [W]
t time [s]
T temperature [°C]
Tr refrigerator temperature [°C]
T∞ ambient temperature [°C]
We electricity power [W]
Wth heat transfer rate [W]
ΔT temperature difference [°C]
Greek symbols
∑ mathematical symbol for summation
μ dynamic viscosity [N s m−2
]
ρ density [kg m−3
]
Abbreviations
COP coefficient of performance
OEM original equipment manufacturers
Subscripts
a thermosyphon adiabatic section
c thermosyphon condenser section
cs climate simulator
e thermosyphon evaporator section
l liquid
Fig. 1 – Thermosyphon placed in a refrigerated space will
remove heat when the ambient temperature is lower than
refrigerated space.
166 i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
4. of the insulation, volume of food added/removed, and the
number and duration of door-opening events.Typical ranges for
Tr are 2.8–4.5 °C (37–40 °F). The total thermal resistance, Rth, in-
cludes all thermal resistances in moving the heat from the air
in the refrigerated space to the ambient air. Since Qr and Tr are
fixed, Rth will dictate the maximum ambient temperature, T∞,
that will provide the required cooling with the thermosyphon.
Minimizing Rth will thus maximize the hours per year that the
system will provide cooling. If the thermosyphon system cannot
provide 100% of the required cooling, the refrigerator will simply
cycle its own vapor-cycle-based refrigeration system so that the
refrigerator contents are not compromised.
Thermosyphons have been used in a variety of engineer-
ing applications, including air–air heat exchangers (Jouhara and
Merchant, 2012; Lukitobudi et al., 1995), protection of perma-
frost degeneration (Zhi et al., 2005), and solar heating systems
(Chow et al., 2006; Esen and Esen, 2005). However, there is little
research into the application of thermosyphons for refrigera-
tion applications by using cold outdoor temperatures. The
SunFrost commercial refrigerator system (SunFrost, 2016) was
developed in the early 1980s. Although the product literature
referred to a heat pipe as the key heat transfer device, it ac-
tually appeared to be a two-phase thermosyphon that was used.
The refrigerator did not achieve significant commercial success
and the product was abandoned after several years. A more
recent study used a SunFrost unit as well as two additional tra-
ditional refrigerators modified to include thermosyphons (Cold
Climate Housing Research Center, 2013). The thermosyphons
in their systems did not have fins or fans in the cabinet to
enhance heat transfer. They also required a temperature dif-
ference of ~21 °C between the refrigeration compartment and
ambient temperature in order to operate, which significantly
limits the hours per year and the locations in which such a
system will work.
In this study, a commercial, freezer-less residential refrig-
erator was retrofitted by installing a thermosyphon and
tangential fans on both the evaporator and condenser section
of the thermosyphon. A climate simulator chamber was built
to simulate a range of outdoor cold temperature conditions.
The impact of the ambient outside temperature, the tempera-
ture distribution inside the refrigerator, the dynamic cooling
performance, and the system’s energy consumption are mea-
sured and discussed.
2. Thermosyphon principles and operation
2.1. Principle of operation
A two-phase closed thermosyphon is a type of heat pipe without
an internal wick (Dunn and Reay, 1982), as shown in Fig. 2. It
is simple in construction and design, consisting of a hollow
tube that is oriented vertically and has been evacuated and
filled with a working fluid. Heat is added at the bottom of the
device in the evaporator,vaporizing the working fluid and causing
it to rise to the top of the device to the condenser. Heat is removed
in the condenser, causing the vapor to condense onto the pipe
wall. The liquid flows back down the sides to the evaporator
by gravity and the process repeats.An optional,insulated middle
section, called the adiabatic section, may be present as well.
The heat transfer mechanisms in the evaporator are more
complicated than those in the condenser because the falling
liquid film and the liquid pool in the bottom of the device par-
ticipate in the phase change and heat transfer simultaneously.
Different heat transfer regimes are possible, depending on the
intensity of the wall heat flux in both liquid film and liquid
pool (El-Genk and Saber, 1998a, 1998b).
Several factors limit to the maximum heat transfer that can
pass through the thermosyphon. Dry-out occurs (Dobran, 1985;
El-Genk and Saber, 1999) when there is not enough working
fluid present, and dry regions form on the evaporator walls.
Conversely, if too much liquid is present, pool flooding occurs,
in which the liquid pool fills and then expands beyond the
evaporator section due to nucleate boiling. The counter-
current flooding limit (Nguyen-Chi and Groll, 1981) occurs at high
vapor velocities where the upward-moving vapor exerts sig-
nificant shear stress on the falling liquid film, causing the film
thickness to increase or separate from the wall completely.
2.2. Thermosyphon model
A simulation model was developed to predict the operating pa-
rameters of the thermosyphon based on its geometry, working
fluid, and thermal boundary conditions. The model allows
varying these parameters to minimize the thermal resistance,
as discussed above. Thermosyphons have been studied exten-
sively in the literature.The model developed by Jiao et al. (2008)
Fig. 2 – Schematic of the two-phase closed thermosyphon.
167i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
5. was adapted for used in this work. The model solves the 1-D
conservation of energy mass and momentum equations in the
evaporator, condenser, and adiabatic section of the
thermosyphon.The liquid film thickness and temperature drop
across the thermosyphon as a function of heat input are pro-
vided from the model. The falling film and liquid pool in the
evaporator are treated independently, with the various boiling
regimes incorporated through empirical relationships in both
the film and the pool. The model also identifies the operating
limits of the thermosyphon, including the flooding, dry out and
sonic limits. The resulting model is represented by a set of
coupled ordinary differential equations that are solved using
the MATLAB®
programming language.
In the simulation, the condenser is treated as a convec-
tive boundary condition and the evaporator as a constant-
heat-flux boundary condition. Strictly speaking, the actual
refrigerator application has convective boundary conditions at
both the evaporator and condenser. The reasons for using the
constant heat-flux boundary condition are that (1) nearly all
prior modeling has adopted this boundary condition, largely
because the expressions for boiling used to determine the heat
transfer in the liquid pool are all based on a heat-flux bound-
ary condition, and (2) the thermosyphon represents only a small
portion of the overall thermal resistance in moving the heat
from the refrigerated space to the ambient; rather the heat
transfer to and from the fins on the evaporator and con-
denser, respectively, dominates the thermal resistance. As such,
the error introduced with a constant-heat flux boundary con-
dition is small when the overall heat transfer is considered
while still allowing the use of well-established models to be
used to predict the thermosyphon operation.
Several candidate working fluids were investigated, includ-
ing methanol, ethanol, R134A, water, and ammonia. First, the
figure of merit FOM, which characterizes a fluid’s expected per-
formance for the thermosyphon based on its thermal properties,
is calculated as follows (ESDU (Engineering Sciences Data Unit),
1983):
FOM
h kfg l l
l
=
⎡
⎣
⎢
⎤
⎦
⎥
ρ
μ
2 3 0 25.
. (2)
Here hfg is the latent heat, ρl the density, kl the thermal con-
ductivity, and μl the liquid viscosity. Larger values of the FOM
are better. The FOM for each working fluid is shown in Table 1.
The 1-D model was also run for each working fluid. Filling
ratios of 5% and 10% and heat inputs of 40 W and 60 W were
considered. The vapor temperature inside the thermosyphon
was taken to be 0 °C, as this represents a typical vapor
temperature for a thermosyphon operating between a 3 °C re-
frigerated space and an ambient outside temperature several
degrees cooler. The exception was for water, in which a 5 °C
vapor temperature was used was used to avoid freezing in the
condenser. The temperature difference between the evapora-
tor and condenser is reported for each fluid, filling ratio and
heat input in Table 1. Lower values of the temperature differ-
ence are better.
Based on the FOM and model results, methanol is chosen
as the working fluid for this application, as it provides good
overall performance for the temperature range needed for the
refrigeration application.Water is ruled out because it will freeze
at outdoor temperatures below 0 °C and its falling liquid film
tends to break up into rivulets due to its high surface tension
and high latent heat in this application (ESDU (Engineering
Sciences Data Unit), 1983). Ammonia is an excellent working
fluid but is ruled out due to its significant health and han-
dling risks, and its strong reactivity with copper.
3. Materials and methods
3.1. Thermosyphon fabrication
A custom copper tube with annular-fins (Fin Tube Products, Inc.)
was acquired to serve as the thermosyphon for this work. The
dimensions of the thermosyphon pipe are shown in Table 2.
The evaporator section is located within the refrigerated
space, and the condenser section is placed within a cold-
climate simulator. The adiabatic section resides between
the evaporator and the condenser. It has no fins and is sur-
rounded with 2.5 cm pipe insulation to minimize heat loss.The
top of the thermosyphon assembly is fitted with a series of ball
valves for evacuation, fluid filling, and pressure monitoring.
Table 1 – Working fluid FOM and temperature difference from simulation.
Working fluid FOM Evaporator-condenser temperature difference (°C)
Q = 40 W Q = 60 W
FR = 5% FR = 10% FR = 5% FR = 10%
Ammonia 4796 0.12 °C 0.11 °C 0.22 °C 0.24 °C
Water 4177 0.31 °C 0.53 °C 0.49 °C 0.81 °C
Methanol 1732 0.47 °C 0.52 °C 0.81 °C 0.89 °C
R134a 993 0.74 °C 0.68 °C 1.03 °C 1.08 °C
Ethanol 1142 0.77 °C 0.88 °C 1.28 °C 1.52 °C
Table 2 – Thermosyphon geometry.
Geometric parameter Value
Total length: L (cm) 227
Evaporator length: Le (cm) 102
Adiabatic length: La (cm) 23
Condenser length: Lc (cm) 102
Inner tube diameter (mm) 17
Wall thickness (mm) 1.2
Fin height (mm) 9.5
Fin thickness (mm) 0.4
Fin spacing (mm) 1.6
168 i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
6. To add the methanol, a vacuum pump and valve system ar-
rangement were used to evacuate the thermosyphon to a
pressure of ~0.01 mmHg, followed by the addition of the desired
volume of methanol. In this work filling ratios, defined as the
ratio of working fluid volume to the evaporator section volume,
of 5% and 10% were used, and were obtained by filling with
15.6 mL and 31.3 mL of methanol, respectively. A low filling ratio
is desirable, as the thermal resistance of the pool is generally
higher than the resistance through the falling liquid film in
the evaporator (Fig. 2) (Shiraishi et al., 1981). The methanol
volume was measured and introduced using a 30 cm3
syringe
and short length of vinyl tubing to avoid introducing air into
the evacuated thermosyphon during the filling procedure.
To remove any residual non-condensable gas in the
thermosyphon, a degassing procedure was conducted before
the test began. The evaporator section was heated with a heat
gun and the condenser section was cooled by the climate simu-
lator to drive the non-condensable gas toward the top
(condenser) region where the filling values are located. The
vacuum pump was then turned on and the vacuum valve
opened for 3–5 s to remove the non-condensable gas.This pro-
cedure was repeated several times.To make up for the possible
loss of methanol working fluids during the degas process, an
additional 2–3 mL of methanol was added during the charg-
ing process mentioned above.
3.2. Experimental configuration
A schematic and image of the experimental setup are shown
in Fig. 3. A commercially available residential refrigerator
(Frigidaire FRU17B2J) is used for the testing. The unit is a re-
frigerator only, with no freezer section. Cooling is maintained
by cycling the OEM refrigeration system on or off; there is no
ability to modulate the delivered cooling. The refrigerator also
incorporates a defrost cycle that runs for 30 minutes after every
12 hours of compressor cumulative running time. During the
defrost cycle, the refrigeration unit pauses and a defrost heater
is switched on, with a measured electrical power rating of 453 W.
The climate simulator chamber is located directly above
the refrigerator.The enclosure is fabricated from 50-mm thick
rigid polystyrene insulation (Owens Corning). A Neslab RTE-
140 chiller provides chilled water to a Koolance liquid–air heat
exchanger plate inside the climate simulator.Six 12VDC 120 mm-
diameter fans provide airflow over the heat exchanger.The air
within the simulator was dried using 0.9 kg of silica gel in a
porous container to avoid ice forming on the heat exchanger.
Six 41.3 cm-length long high-efficiency 24-VDC tangential
fans (Ebmpapst) are used to force air over the thermosyphon
evaporator and condenser. Three fans are located in the re-
frigerated section, and the remaining three are located in the
climate simulator. The fans are placed 2–3 cm from the
thermosyphon, and aluminum sheet is used to duct the airflow
through the thermosyphon fins. The fans can be individually
turned on or off, and their speed modulated by using pulse-
width-modulation from a microcontroller.
Temperature measurements in the refrigerator and the
climate simulator were made using DS18B20 digital tempera-
ture sensors (Dallas Semiconductor), which have a stated
accuracy of ±0.5 °C. These sensors were located in the refrig-
erator space at the center of the top, middle, and bottom
Fig. 3 – Experimental schematic of the thermosyphon-assisted cooling system (left), overall setup for the thermosyphon-
assisted cooling system (temperature sensors not shown, right).
169i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
7. shelves. Four additional sensors were located in the top, middle
and bottom portions of the climate simulator.The ambient tem-
perature of the room in which the refrigerator operates was
monitored using an Oregon THGR268 sensor, which has a stated
accuracy of ±1.0 °C. An Arduino Uno microcontroller was used
for data acquisition and control.
Two Keithley 2000 digital multimeters were employed to
measure the current and voltage of the fans to determine their
electrical power consumption. To measure the power con-
sumption of the refrigerator’s own cooling system, a Watts Up?
PRO AC meter was used. To provide an accurate average of the
power usage, data was collected for 23 h.
When testing the thermosyphon cooling system, the re-
frigerator was unplugged to eliminate any cooling contribution
from the refrigerator’s own cooling system. All fans were turned
on, and the chiller temperature was then adjusted to obtain
the target temperature in the climate simulator. The system
was maintained in this condition until the refrigerator, the
climate simulator, and ambient room temperatures stabi-
lized (typically 2–4 h). The refrigerator door remained closed
at all times during the test.
4. Results and discussion
A series of tests were performed in order to investigate the per-
formance of the thermosyphon-assisted cooling refrigerator
system.
4.1. Original refrigerator COP
The cooling performance of the refrigerator’s original equip-
ment manufacturer (OEM) cooling system was determined to
provide a comparison to the thermosyphon-assisted cooling
system. The overall coefficient of performance (COP) is defined as
follows:
COP
Q
P
c
re
≡ (3)
Here Qc is the heat removed from the interior of the re-
frigerator and discharged to the room surroundings, and Pre is
the electrical power consumed by the refrigerator compressor
and fans. The interior light was disabled to avoid its contri-
bution to the electrical and thermal loads. The heat flow is
determined as follows. When the refrigerator is in steady state,
and in the absence of door-open events, the cooling system
removes the heat that migrates into the refrigerator interior,
Qc0 . To determine Qc0, a series of additional heat inputs Qin
was added to the refrigerator and the increase in the refrig-
erator electricity consumption was recorded. The relationship
between Pre and Qin thus becomes
P
COP
Q Qre c in= +( )1
0 (4)
The heat load was provided with two 100 W incandescent
light bulbs placed at the bottom of the refrigerated space. The
bulbs were covered with aluminum foil to minimize radia-
tion heat transfer to the temperature sensors. Electrical power
to the bulbs was adjusted using a variable AC transformer
(Variac), while the voltage and current were measured after the
transformer using two Keithley 2000 multimeters. The bulb
power was varied from 0 to 120 W in 20 W increments. The
number of refrigerator defrost cycles was one or two, depend-
ing on the heat load, with higher heat loads yielding an extra
defrost cycle due to the increased compressor run time. The
refrigerator interior temperature was maintained at
3.5 °C ± 0.6 °C using the OEM cooling system and ambient room
temperature was 21.9 °C ± 1.1 °C during the tests.
The results are shown in Fig. 4, plotted as the bulb heat
power versus OEM refrigerator electrical power consump-
tion. As can be seen, the power consumption is nearly linear
with the heat load. The slope of the line is 0.68 (We/Wth). The
reciprocal of this value 1.47 (Wth/We) is the overall COP of the
Fig. 4 – Refrigerator’s own cooling system’s energy consumption vs. heating elements’ (bulbs) power.
170 i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
8. refrigerator from Eq. (4). The estimated electricity use with no
lamp load is 28.7 W ± 0.3 W, which corresponds to the normal
heat leakage into the refrigerated section in the absence of any
internal heat load. From the slope of the regression line in Fig. 4,
the heat load Qc0 is estimated to be 42.2 ± 0.7 W.
4.2. Steady state operation of thermosyphon-assisted
cooling system
The first series of tests with the thermosyphon cooling system
were done for steady-state operation of the refrigerator in which
the door remains closed, and all items within the refrigerator
are in thermal equilibrium with the refrigerated space. The
only heat loads in this case are: (1) the heat leakage into the
refrigerator, which is largely independent of the food load,
and (2) any heat provided by the defrost cycle. There are two
goals: (1) minimize the temperature between the outside
ambient temperature and the refrigerated space, and (2) provide
this minimal temperature with as little electricity use for the
fans as possible.
The following parameters were varied for this test: (1) tem-
perature of climate simulator, (2) number of fans in operation
in the refrigerated compartment, and (3) filling ratio of the
thermosyphon. All three fans in the climate simulator were
run for all tests. The climate simulator temperatures ranged
from −5.1 °C to −0.6 °C. The lower value represents the coldest
temperature that the chiller was able to produce in the climate
simulator, while the upper limit was selected to ensure that
the refrigerator interior temperature would not exceed the
maximum FDA-recommended temperature of 4.5 °C (40 °F) to
avoid spoilage of perishable items (U.S. Food and Drug
Administration, 2016).
The thermosyphon fans in the refrigerator space were turned
on in the following combinations: (i) all fans on, (ii) all fans
off, (iii) top and bottom fans on, (iv) top fan only, (v) middle
fan only, and (vi) bottom fan only. When turned on, the fans
ran at full speed. These combinations were chosen to assess
the thermal performances vs. additional electricity cost for
the fans. Also, there is a thermal penalty for using more fan
power because the electricity provided to the fans represents
an additional heat load that must be removed from the re-
frigerated space. Thermosyphon fill ratios of 5% and 10% were
tested to determine if a significant performance difference
was observed.
Temperatures were reported separately for the bottom,
middle, and top shelves in the refrigerated space. This is
necessary to both assess temperature stratification as well as
account for situations when different combinations of fans are
turned on or off. Each test was run for at least 12 hours after
the system reached steady state.
The results are shown in Fig. 5 and Fig. 6. A 5% filling ratio
is used in all cases, except in 7(d), in which 10% filling ratio is
used. In Fig. 5a, all three fans are on, which represents the
maximum cooling capability, at the expense of the most elec-
tricity used, and the largest heat addition to the refrigerated
space. Temperatures at the top, middle, and bottom shelves
are presented for several climate-simulator temperatures. The
temperature difference between the refrigerator and climate
simulator remained nearly constant at 5.0–5.5 °C, regardless
of the climate simulator temperatures or shelf position. The
bottom shelf was about 1 °C warmer than the middle and top
shelves, which is likely due to the liquid pool located at the
bottom of the thermosyphon, which has a higher thermal re-
sistance than the evaporating film on the walls above the pool
(Fig. 2) (Shiraishi et al., 1981).
In Fig. 5b, the bottom fan is shut off. The distribution of top
shelf temperature and bottom shelf temperature is nearly the
same as for all fans on. However, the middle shelf tempera-
ture has increased by more than 0.5 °C relative to the top shelf,
even though its fan remains on. The increase may be due to
heat flow from the bottom shelf via natural convection.
The temperature data for top, middle, and bottom fans op-
erating individually are shown in Fig. 6a–c, respectively. As
expected, the shelf next to the fan that is on has a lower tem-
perature compared to the other two shelves. However, the
overall temperature in the space varied considerably depend-
ing on which fan is on. For the case of the top fan on only, the
middle and bottom shelf temperatures are still marginally in
Fig. 5 – Temperature distribution inside the cabinet at 5% thermosyphon filling ratio. (a) All three fans in refrigerated section
are on, (b) top and middle fans on, bottom fan off.
171i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
9. the acceptable range of 4.5 °C or less. For the middle or bottom
shelf fans on, however, the temperatures in the refrigerated
space are considerably higher, and would be unacceptable in
most conditions. Explanations for this variation include the
poorer performance of the liquid pool at the bottom of the
thermosyphon mentioned above. Buoyancy effects may also
be coming into play, as air cooled near the upper region of the
refrigerated space will sink to the bottom, whereas cooler air
already at the bottom will tend to remain there.
Shelf temperatures for a filling ratio of 10% are shown in
Fig. 6d.There is no distinct difference from those for a 5% filling
ratio. As such, a low filling ratio works well for this applica-
tion and an exact filling ratio does not appear to be necessary.
Care should be taken, however, to ensure that none of the
traditional thermosyphon limits are exceeded for normal
refrigeration operation.
The case for all fans off in both the refrigerated space and
the climate simulator yielded a large temperature difference
between the two spaces. When the climate simulator tem-
perature was −2 °C, the refrigerated space rose to nearly
20 °C. This suggests that very cold outside conditions can be
accommodated by simply shutting all fans off to prevent freez-
ing the food in the refrigerator.
4.3. Thermal diode test
The thermal diode effect, in which the thermosyphon auto-
matically shuts down when the ambient temperature exceeds
the interior temperature, was evaluated as follows. All fans
in the refrigerator and the climate simulator were turned off,
and the refrigerator was provided with AC power so that the
OEM cooling system would chill the refrigerated space to 2 °C.
The power consumption of the refrigerator was then mea-
sured for the climate simulator set at temperatures of 2 °C and
then 28 °C, representing a winter and summer day, respectively.
The energy consumption for the 28 °C simulated hot weather
condition was only about 2.5 W larger than that for the 2 °C
condition. The thermosyphon device is thus conformed to be
shutting down once the ambient temperature approaches that
of the refrigerated space.The higher energy consumption may
result from additional heat leakage due to the fact that the room
was about 2 °C warmer when the 28 °C case was run.
Fig. 6 – Temperature distribution inside the cabinet, (a–c) top fan’s operation, middle fan’s operation, bottom fan’s
operation, these three operations are at 5% filling ratio, (d) fan operations at 10% filling ratio.
172 i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
10. 4.4. Transient cooling test
Refrigerators must cool food and beverage items to the con-
ditioned temperature after they are initially placed in the
refrigerated space. This transient cooling event requires re-
moving the heat in the food in as short of time as possible to
maintain freshness (Fukuyo et al., 2003). The Japanese Indus-
trial Standard (JIS) test protocol was used for this test, as it is
the only known standard to specify transient load test for re-
frigerators (Geppert, 2011). Eight 500-mL water bottles were used
to simulate the food thermal load. The water bottles were ini-
tially at room temperature (23–24 °C), then they were placed
in the refrigerated space. A waterproof DS1820 temperature
sensor was placed within one bottle to monitor the water tem-
perature as it was cooled. Two test cases were run, as well as
a reference case using the OEM refrigeration system. The lo-
cation, fan configuration, and start/end temperatures for each
are shown in Table 3.
The results are shown in Fig. 7. As can be seen, for both
cases, the thermosyphon-assisted cooling system cooled the
water more rapidly than the OEM refrigeration system.The total
heat removal from water can be determined by
Q mC Tp ii
N
= ( )=∑ Δ1
(5)
where m = 4 kg is the mass of water in the eight 500 mL bottles,
Cp = 4180 J kg−1
K−1
is the specific heat of water, and ΔTi is the
decrease of the water temperature in the ith measurement in-
terval. Eq. (5) is plotted in Fig. 8.The accumulated heat removal
increased rapidly shortly after the thermal load is placed in
the refrigerator load. The thermosyphon cooling system
removed heat from thermal load more rapidly than refrigera-
tor OEM cooling system in the same amount of time, Near the
end of the measurement for Case 1 at ~500 min the water
temperature increased nominally due to a slight increase in
temperature inside the climate simulator.
4.5. Power consumption, cost and further opportunities
for optimization
Almost the entirety of the thermosyphon-assisted cooling sys-
tem’s electrical usage is from the fans in the refrigerated space
and climate simulator (six total), with a negligible amount of
power used to run the microcontroller (250 mW). The power
for each fan was measured and is summarized in Table 4. The
measurement error for each fan is ±0.04 W.
The total power use when all three fans are on is about 27 W,
which is comparable to the power used by the OEM refrigera-
tion system at steady-state conditions.This value can be further
reduced if it is possible to shut off one or more fans, depend-
ing on the outside conditions.
Table 5 presents cost and savings analysis for several rep-
resentative cities in the U.S. Typical metrological year (TMY)
data (NREL, 2008) are used to determine the number of hours
Table 3 – Transient test cases.
Case Water location Thermosyphon
fan use
Water start
temperature (°C)
Water end
temperature (°C)
Climate simulator
temperature (°C)
Case 1 Middle shelf Top fan only 24.3 3.7 −2.2
Case 2 Top shelf Top and middle fans 23.9 2.0 –4.0
Reference Middle shelf N/A (OEM refrigeration used) 23.0 2.9 N/A
Fig. 7 – Dynamic cooling test: (a) Case 1: thermal load on the middle shelf, top and middle fans on, Tcs = − °2 2. C; (b) Case 2:
load on the top shelf, top fan on only, Tcs = − °4 0. C. The yellow dashed line is the reference case using the OEM refrigeration.
173i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
11. per year when the outside temperature is less than 4.4 °C, and
it is assumed that the thermosyphon system will carry the re-
frigeration load completely in this case. Only the top fan is used
in this case, which represents the maximum potential energy
savings of the current system.The regional current (2016) elec-
tricity rate is used for each city.
There are several opportunities to improve the perfor-
mance of the current system. These include:
• Incorporate high-efficiency PWM fans.The tangential fans were
used in this work for their small size and outlet duct
geometry that allowed easy coupling to the thermosyphon
fins. For optimal energy savings, other fan geometries may
provide similar airflow at reduced energy consumption. In
particular, low-voltage DC square, axial “muffin” fans are
inexpensive, efficient, come in a variety of form factors, and
can be driven directly by solar panels.
• Remove thermal contribution from fan heating. The power con-
sumed by the fans in the refrigerated space, which can be
up to 13.2 W, is converted to heat that must be removed from
the refrigerated space. At steady state conditions, this power
can represent an additional 30% thermal load, beyond the
42.2 W of normal leakage current. Arranging the fan motors
to reside outside of the refrigerated space would remove this
thermal burden from the system. The fan mounting would
be more complicated, as the fan motor shaft would be re-
quired to penetrate the refrigerated space envelop, however
the energy savings would be significant.
Fig. 8 – Total heat removed from food: (a) Case 1: thermal load on the middle shelf, top and middle fans on, Tcs = − °2 2. C;
(b) Case 2: load on the top shelf, top fan on only, Tcs = − °4 0. C. Yellow line is the reference case using the OEM refrigeration.
Table 4 – Power usage by fans.
Device Fan Power
Climate simulator All three fans together 13.7 W
Refrigerator cabinet Top fan power 4.5 W
Middle fan power 4.5 W
Bottom fan power 4.2 W
Total power 26.9 W
Table 5 – Estimated energy savings by location in U.S.
City Electricity cost
US$/kWhr
Thermosyphon system
annual usage
Total energy saving
(kWhr)
Annual bill
saving (US$)
20-year bill saving
(US$)*
New York, NY 0.177 6% 24.9 4.40 88
Washington, D.C. 0.137 8% 32.9 4.50 90
Philadelphia, PA 0.145 8% 33.8 4.90 98
Boston, MA 0.192 10% 40.2 7.70 154
Columbus, OH 0.130 13% 51.7 6.70 134
Denver, CO 0.117 13% 52.2 6.10 122
Ann Arbor, MI 0.154 14% 55.8 8.60 172
Chicago, IL 0.132 16% 63.4 8.40 168
Des Moines, IA 0.130 18% 70.6 9.20 184
Minneapolis, MN 0.131 25% 100.1 13.10 262
* Assumes electricity price remains fixed for entire period.
174 i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 7 4 ( 2 0 1 7 ) 1 6 5 – 1 7 6
12. • Eliminate condenser fans. It may be possible to eliminate the
condenser fans completely. Space is much less of an issue
outside of the house envelope, hence considerably larger
fins can be used, as well as a longer condenser section. The
fin design can also factor in local average wind speeds. It
may thus be possible to design the condenser heat
exchanger so that no fans are required. If fans are neces-
sary, it may be possible to shut them down when the wind
speed is sufficient to provide additional energy savings.
• Optimize the fin structure on the thermosyphons. The current
fin type and spacing were restricted by the availability of
a tubing manufacturer to provide. An optimized fin con-
figuration in terms of fin spacing, fin length, shape (simple,
louvered, etc.) would maximize heat transfer with minimal
airflow and pressure drops, which would also reduce the
required fan power (Rohsenow et al., 1998; Shah and Sekulic,
2003; Webb and Kim, 1994).
5. Micro-climate concept
As shown in Fig. 7, the temperature in the refrigerated space
can vary substantially with the thermosyphon-assisted cooling
system, depending on which fans are on. This can be used as
an advantage to save additional electricity by implementing
a micro climate in the refrigerated space.The idea is to have only
a portion of the refrigerator maintained at or below the target
of 4.4 °C or less for perishable foods, while other regions of the
refrigerator can be run warmer for foods and beverages that
favor slightly higher temperatures and/or are not susceptible
to spoilage. Examples of the latter include canned and non-
dairy beverages, water, condiments, bread, fruits, and vegetables
(European Food Information Council, 2001). In contrast, a tra-
ditional refrigerator cooling system cools the entire space to
the same temperature.The refrigeration system’s OEM cooling
system can be used to ensure the cold-temperature regions of
the refrigerator are not exceeded.
In addition, the results in Fig. 5 and Fig. 6 suggest that
the optimal configuration for a micro-climate configuration
would be to run the top fan only, with the top shelf serving
as the coldest portion of the refrigerator. Temperature sensors
placed on each shelf can be used to drive the corresponding
fan for that shelf. The shelves could be thermally insulated,
and color-coded, e.g., blue, green, red for cold, chilled, and cool
shelves, respectively, for easy recognition. The user could
have the option of adjusting each shelf temperature as desired,
and the microcontroller could also report total energy usage
and temperature history as feedback to maximize energy
savings. In commercial refrigeration examples, food items can
be separated by their required storage temperature to ensure
that spoilage or cross contamination does not occur.
Another very important consequence of allowing warmer
refrigeration temperatures is that the proposed refrigeration
concepts can be used in significantly warmer climates and/
or for more hours per year. As discussed earlier, the coldest
achievable refrigeration temperature is directly related to the
outside temperature. By allowing the refrigeration tempera-
ture to rise, the warmer portions of the refrigerator can use
thermosyphon cooling for a larger number of hours per year.
6. Conclusions
This article presents a thermosyphon-based cooling system for
residential and commercial refrigeration systems. The system
uses cold outside temperatures to provide low-cost cooling for
energy savings. Tests were performed on a residential refrig-
erator and a thermosyphon made from a finned copper tube.
Outdoor conditions were simulated with a cooled air space
above the refrigerator. It was found that the refrigerated space
can be maintained within ~5 °C of the outside ambient tem-
perature for a range outside temperatures. The impact of the
outdoor air temperature and the fans was investigated. Tem-
peratures below the maximum recommended temperature of
4.4 °C were achieved with outside temperatures as high as
−0.8 °C. Using fewer fans increases some regions of the refrig-
erated space temperature. A micro-climate concept is proposed
in which only a portion of the refrigerator is cooled below the
4.4 °C target, while the balance of the refrigerator runs slightly
warmer.
Opportunities for further work include optimizing the fan
and fin configuration to minimize the fan electricity consump-
tion, moving the fan motors outside of the refrigerated space
to eliminate their thermal load, and incorporating thermal
energy storage to capitalize on lower temperatures at night.
Another concept is to use the thermosyphons to cool the con-
densers on a normally operating refrigeration system. By
reducing the average condenser temperature, the overall COP
will increase. Furthermore, since the condenser temperature
is typically well above the ambient room temperature, this
would allow the system to be used for a larger fraction of the
year in many regions of the country.
Acknowledgments
This work was supported by the U.S. Department of Energy and
Lawrence Berkeley National Laboratory 2012/2013 Max Tech and
Beyond Program, Grant No. 7038944.
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