This document summarizes research analyzing heat losses in a compact Fresnel linear reflector solar power system with trapezoidal absorbers. The system aims to directly heat water to generate steam, improving efficiency over thermal oil systems. Heat loss is analyzed through adjusting cavity angles, depths, and insulation thickness. A thermal resistance circuit model is used to calculate heat losses from the absorber and cavity through convection and radiation. The goal is to determine the most efficient configuration for this concentrated solar power technology.
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.
Efficiency Analysis For an Experimentally Set-up Double-Pass V-Corrugated Sol...Aakanksha Dubey
This paper presents the efficiency analysis of an experimental set-up double-pass V-corrugated solar air heater. All
the experimental results were obtained with the developed solar air heater kept at an inclination angle of 23.5
degrees (Latitude Angle of Bhopal, India), facing due south, and using DC fans (for forced convection) with
different air flow rates. The efficiency results, gathered on two consecutive typical Indian peak summer days, are
presented taking into consideration the intermittent availability of sunlight at different times on these days. All the
relevant design aspects of the developed double-pass V-corrugated solar air heater such as the material used for
insulation, construction of the outer enclosure, and the solar air heater assembly, are discussed.
1. This document describes solar thermal desalination systems that use multi-layer heat recovery to improve energy efficiency. Heat from evaporation is recovered in successive layers, requiring less energy input.
2. Three prototype systems were tested - using flat plate collectors, parabolic reflectors, and evacuated tubes. Measurements showed the flat plate system produced 44kg of water over 24 hours with 98% energy efficiency.
3. Dynamic simulations using Matlab/Simulink accurately modeled the multi-stage process and predicted annual performance at other locations. Optimization continues to further reduce energy requirements.
CFD Analysis of a Heat Collector Element in a Solar Parabolic Trough Collector iMentor Education
A numerical study of the performance of a solar Parabolic Trough Collector (PTC) has been done focusing on its receiver. The receiver consisting of a glass-shield enclosing a Heat Collector Element (HCE) with vacuum in the annular space has been subjected to seasonal and diurnal variations of solar radiation along with the
concentrated heat flux reflected from the parabolic trough mirror for conditions at Pune, India. The HCE is modeled as a metallic tube with thermic fluid Therminol-VP1TM flowing through it at low Reynolds number under thermally developing conditions with highly temperature dependent properties. The highly asymmetric
nature of the physics for thermal and turbulent flow conditions make it imperative to consider a complete three dimensional domain for the conjugate heat transfer analysis. The conduction, convection and radiation heat transfer effects have been modeled with radiation restricted within the annular region using the S2S radiation
model. The solar fluxes have been modeled using the Solar Load Model also accounting for the shadowing effects for semi-transparent and opaque surfaces. The pressure drop in the thermic fluid flow is comparatively uniform throughout the day during winter conditions while the fluid gets heated up 4 times more at noon
compared to morning. The summer conditions exhibit a 2.5 times higher pressure drop at noon compared to the morning conditions. The comprehensive analysis is performed using the finite volume based CFD code of ANSYS FLUENT 12.1 and verifies the huge potential that PTC holds for high temperature applications in
concentrated solar power plants.
A solar ejector cooling system using refrigerant r141bMark Murray
This document describes a solar ejector cooling system that uses R141b as the working fluid. Key points:
- The system achieves a high coefficient of performance (COP) of 0.5 experimentally for single-stage cooling at a generation temperature of 90°C, condensing temperature of 28°C, and evaporating temperature of 8°C.
- For solar cooling, the overall COP is estimated to be around 0.22 at a generation temperature of 95°C, evaporating temperature of 8°C, and solar radiation of 700 W/m2.
- The solar ejector cooling system is simpler than absorption cooling systems and has potential for solar refrigeration applications with an optimum overall
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.
Thermo Acoustic refrigeration is a phenomenon that uses high intensity sound waves in a pressurized gas tube to pump heat from one place to other to produce refrigeration effect. This system completely eliminates the need for lubricants and results in 40% less energy consumption.
This document describes a mini project on thermo-acoustic refrigeration. It discusses the design and fabrication of a thermo-acoustic refrigerator prototype using a standing wave resonator with air as the working fluid. The prototype was unable to demonstrate a distinguishable thermo-acoustic refrigeration effect due to issues with the heat exchange process, where heat from the hot region did not exit the system properly. The document also provides background on thermo-acoustic refrigeration and outlines its potential advantages over conventional refrigeration techniques.
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.
Efficiency Analysis For an Experimentally Set-up Double-Pass V-Corrugated Sol...Aakanksha Dubey
This paper presents the efficiency analysis of an experimental set-up double-pass V-corrugated solar air heater. All
the experimental results were obtained with the developed solar air heater kept at an inclination angle of 23.5
degrees (Latitude Angle of Bhopal, India), facing due south, and using DC fans (for forced convection) with
different air flow rates. The efficiency results, gathered on two consecutive typical Indian peak summer days, are
presented taking into consideration the intermittent availability of sunlight at different times on these days. All the
relevant design aspects of the developed double-pass V-corrugated solar air heater such as the material used for
insulation, construction of the outer enclosure, and the solar air heater assembly, are discussed.
1. This document describes solar thermal desalination systems that use multi-layer heat recovery to improve energy efficiency. Heat from evaporation is recovered in successive layers, requiring less energy input.
2. Three prototype systems were tested - using flat plate collectors, parabolic reflectors, and evacuated tubes. Measurements showed the flat plate system produced 44kg of water over 24 hours with 98% energy efficiency.
3. Dynamic simulations using Matlab/Simulink accurately modeled the multi-stage process and predicted annual performance at other locations. Optimization continues to further reduce energy requirements.
CFD Analysis of a Heat Collector Element in a Solar Parabolic Trough Collector iMentor Education
A numerical study of the performance of a solar Parabolic Trough Collector (PTC) has been done focusing on its receiver. The receiver consisting of a glass-shield enclosing a Heat Collector Element (HCE) with vacuum in the annular space has been subjected to seasonal and diurnal variations of solar radiation along with the
concentrated heat flux reflected from the parabolic trough mirror for conditions at Pune, India. The HCE is modeled as a metallic tube with thermic fluid Therminol-VP1TM flowing through it at low Reynolds number under thermally developing conditions with highly temperature dependent properties. The highly asymmetric
nature of the physics for thermal and turbulent flow conditions make it imperative to consider a complete three dimensional domain for the conjugate heat transfer analysis. The conduction, convection and radiation heat transfer effects have been modeled with radiation restricted within the annular region using the S2S radiation
model. The solar fluxes have been modeled using the Solar Load Model also accounting for the shadowing effects for semi-transparent and opaque surfaces. The pressure drop in the thermic fluid flow is comparatively uniform throughout the day during winter conditions while the fluid gets heated up 4 times more at noon
compared to morning. The summer conditions exhibit a 2.5 times higher pressure drop at noon compared to the morning conditions. The comprehensive analysis is performed using the finite volume based CFD code of ANSYS FLUENT 12.1 and verifies the huge potential that PTC holds for high temperature applications in
concentrated solar power plants.
A solar ejector cooling system using refrigerant r141bMark Murray
This document describes a solar ejector cooling system that uses R141b as the working fluid. Key points:
- The system achieves a high coefficient of performance (COP) of 0.5 experimentally for single-stage cooling at a generation temperature of 90°C, condensing temperature of 28°C, and evaporating temperature of 8°C.
- For solar cooling, the overall COP is estimated to be around 0.22 at a generation temperature of 95°C, evaporating temperature of 8°C, and solar radiation of 700 W/m2.
- The solar ejector cooling system is simpler than absorption cooling systems and has potential for solar refrigeration applications with an optimum overall
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.
Thermo Acoustic refrigeration is a phenomenon that uses high intensity sound waves in a pressurized gas tube to pump heat from one place to other to produce refrigeration effect. This system completely eliminates the need for lubricants and results in 40% less energy consumption.
This document describes a mini project on thermo-acoustic refrigeration. It discusses the design and fabrication of a thermo-acoustic refrigerator prototype using a standing wave resonator with air as the working fluid. The prototype was unable to demonstrate a distinguishable thermo-acoustic refrigeration effect due to issues with the heat exchange process, where heat from the hot region did not exit the system properly. The document also provides background on thermo-acoustic refrigeration and outlines its potential advantages over conventional refrigeration techniques.
Investigation of solar cooker with pcm heat storageiaemedu
This document summarizes an experimental investigation of a solar cooker with phase change material (PCM) heat storage for use in high altitude places like Taif City, Saudi Arabia. The solar cooker system consists of evacuated tube solar collectors connected to a hot water storage tank. The base of the solar cooker box is connected to a copper tube heat exchanger inside a cylindrical pot filled with paraffin PCM. Hot water from the solar collectors is circulated through the heat exchanger to store thermal energy in the PCM and heat the cooking pot. Parameters like solar radiation, humidity, cooker orientation, and ambient temperature were evaluated. The study shows this system can effectively cook and heat food under high altitude conditions with partial cloud cover and moderate
The document presents the results of an experimental analysis of a flat plate solar collector with an integrated latent heat storage unit using phase change material (PCM). Tests were conducted over 60 days from October 2016 to March 2017 in Colombia. The collector reached an average thermal efficiency of 24.11% and a maximum outlet temperature of 50°C. While the PCM provided stability to outlet temperatures during cloudiness, it was unable to supply thermal energy after sunset likely due to a short charging time where the absorber plate temperature reached the PCM melting point. Using a PCM with a lower melting point may increase charging time and improve performance.
IRJET- Efficiency Improvement and Performance Analysis of Solar Collector...IRJET Journal
This document discusses using nanofluids to improve the efficiency of solar collectors. It summarizes the design and fabrication of a flat plate solar collector that uses different shaped copper tubes (circular, triangular, square) as absorber tubes. A computational fluid dynamics (CFD) simulation was performed and results were validated through experimentation on a fabricated solar collector setup. The goal was to increase collector efficiency by changing the absorber tube geometry to increase surface area for heat transfer.
This document discusses thermoacoustics, which uses thermal energy to generate or amplify sound waves. It describes how sound waves can be amplified through heat and used to drive a piston. The key components of thermoacoustic systems are the driver, resonator, stack, and heat exchangers. The resonator contains gas that undergoes compression and cooling from the sound waves. The stack facilitates heat transfer through many small parallel channels. Thermoacoustic systems can be used for refrigeration and have benefits like being environmentally friendly.
This document discusses thermoacoustic engines (TAEs). TAEs use sound waves to pump heat from one place to another, or use a heat difference to induce sound waves. They have no moving parts, making them reliable with a long lifespan. The document outlines the history and discovery of TAEs. It describes the thermodynamic cycle and types of TAEs, including standing wave and traveling wave systems. Components like the heat exchanger, resonator, stack, and regenerator are also explained. The performance, advantages of no moving parts and environmental friendliness, and limitations like low power density of TAEs are summarized.
This document summarizes solar energy utilization in India and types of solar collectors. It discusses that India has high solar potential with about 300 sunny days per year. The key types of solar collectors are flat plate collectors and focusing collectors. It also reviews various artificial roughness geometries that can be used to enhance heat transfer in solar air heaters, such as transverse ribs, V-shaped ribs, and dimples. Experimental studies on single and double pass solar air heaters with different rib configurations are presented.
The document describes two solar powered liquid desiccant cooling systems. The first system was constructed by K. Gommed et al to air condition offices in Haifa, Israel using lithium chloride (LiCl) solution. It achieved a thermal COP of around 0.8 and removed 16 kW of latent heat on average. The second system, studied by Rajat Subhra Das et al for tropical climates like Delhi, India, used LiCl solution and various heat exchangers. It achieved a maximum moisture removal rate of 1.6 g/s and a COP between 0.4-0.8 depending on ambient conditions, with higher COP and capacity at higher ambient humidity levels. Both systems demonstrated the viability of solar
Aia Csi Transpired Solar Collector June2007Sunreps
This document provides information on transpired solar collectors for fresh air heating systems. It discusses how transpired solar collectors work, capturing solar energy through perforated panels to preheat outdoor air drawn into buildings. It outlines key factors to consider for solar collector performance like orientation, climate, solar absorptivity, available solar radiation, ventilation requirements, collector wall area, and air flow rate. The document also notes benefits of these systems for both heating and cooling seasons.
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.
Review of magnetic refrigeration system as alternative to conventional refrig...Naji Abdullah
The refrigeration system is one of the most important systems in industry.
Developers are constantly seeking for how to avoid the damage to the environment. Magnetic
refrigeration is an emerging, environment-friendly technology based on a magnetic solid that
acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials,
MCE warms as the magnetic moments of the atom are aligned by the application of a magnetic
field. There are two types of magnetic phase changes that may occur at the Curie point: first
order magnetic transition (FOMT) and second order magnetic transition (SOMT). The
reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle),
where the magnetic material matrix works both as a refrigerating medium and as a heat
regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer
medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating
fashion through the regenerator made of magnetocaloric material that is alternately magnetized
and demagnetized. Many magnetic refrigeration prototypes with different designs and software
models have been built in different parts of the world. In this paper, the authors try to shed
light on the magnetic refrigeration and show its effectiveness compared with conventional
refrigeration methods.
DESIGN, SIMULATION AND ANALYSIS OF A HYBRID-TYPE (PV/T) SOLAR AIR HEATER FOR ...ijiert bestjournal
This paper deals with the numerical analysis of a H ybrid-Type (PV/T) Solar Air Heater and a study on t he effect of various design parameters that enhance th e performance of the system. The heat transfer improvement in general may be achieved by increasin g the heat transfer coefficient or by increasing th e surface area or by increasing both. The main object ive of the present work is to determine the optimum air mass flow rate at which PV/T systems are to be oper ated and to develop an optimal design of a hybrid t ype (PV/T) solar air heater that shows better performan ce at various heat fluxes due to solar radiation. T his study determines the set of design parameters which lead to the best annual yield of the system. In th is study of a hybrid type (PV/T) solar air heater ICEM CFD (ANSYS) is used to obtain the optimum results,there by increasing the efficiency of the system.
This document summarizes a study that developed a calculation technique to determine the optimal size of flat panel solar thermoelectric systems for combined heat and power production. The technique directly calculates the heat and electric power output based on system parameters like solar irradiation, thermoelectric generator size, and temperatures. The technique was validated through experiments with five commercial thermoelectric generators of varying sizes. Both the calculated and measured results showed there is an optimum system size that achieves maximum heat and electric power output, demonstrating the effectiveness of the developed calculation technique.
International Journal of Computational Engineering Research(IJCER) ijceronline
nternational Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
Thermo acoustic refrigeration uses high intensity sound waves in a pressurized gas tube to pump heat from one place to another and produce a refrigeration effect without lubricants, resulting in 40% less energy consumption. It takes advantage of sound waves reverberating within devices to convert a temperature differential into mechanical energy or vice versa. Applications include liquefying natural gas, chip cooling, refrigerating food, and air conditioning buildings.
A Detailed Review on Artificial Roughness Geometries for Optimizing Thermo-Hy...IJMER
It is well known fact that the heat transfer coefficient between the absorber surface of solar air collector & flowing fluid i.e. air can be improved by providing artificial roughness geometry on heat transfer surface (absorber surface).In this way the Thermal efficiency is increased. But at the same time due to roughness geometry pumping power of solar air collector in increased due to fictional losses in duct. So it necessary to examine the shape, size & flow pattern of various roughness elements to get maximum efficiency with minimum frictional losses. Therefore the selection of roughness geometry has to be based on the parameter that takes into account both Thermal & Hydraulic (friction) performance i.e. Thermo-hydraulic Performance of Solar air collector. Number of roughness elements has been investigated on heat transfer & friction characteristics of solar air collectors. In this paper, reviews of various artificial roughness elements used as passive heat transfer techniques, in order to improve Thermo-hydraulic performance of solar air collectors is reviewed & presented. Correlations developed by various researchers with the help of experimental results for heat transfer & friction factor for solar air collector by taking different roughness geometries are given & these correlations are useful to predict the Thermo-hydraulic performance of solar air collector having roughened ducts. The objective of this paper is also the awareness of effect of various types’ roughness geometries on heat
This document summarizes a research article that developed a simulation application to optimize the position and number of solar collectors in an array to maximize annual energy gain and thermal efficiency. The article describes analyzing a solar collector array system in Macedonia with collectors at different tilts, orientations, and hydraulic connections. It developed a simulation program using the INSEL programming language to perform parametric runs and optimization. Two scenarios were compared: changing the tilt of southeast oriented collectors from 35 to 25 degrees, and retaining the existing 35 degree tilt but adding more collectors. Scenario 1 resulted in over 13% more annual energy gain, while Scenario 2 had 2% higher thermal efficiency.
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.
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.
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.
This document describes the cranial nerves, including their origins, pathways, and functions. It discusses the 12 pairs of cranial nerves, beginning with the olfactory nerve (CN I) and ending with the hypoglossal nerve (CN XII). For each nerve, it outlines where the nerve originates in the brain, the pathways it follows through the skull and other structures, and the structures it innervates or provides sensation to. The document focuses on describing the individual cranial nerves in detail for educational purposes.
Investigation of solar cooker with pcm heat storageiaemedu
This document summarizes an experimental investigation of a solar cooker with phase change material (PCM) heat storage for use in high altitude places like Taif City, Saudi Arabia. The solar cooker system consists of evacuated tube solar collectors connected to a hot water storage tank. The base of the solar cooker box is connected to a copper tube heat exchanger inside a cylindrical pot filled with paraffin PCM. Hot water from the solar collectors is circulated through the heat exchanger to store thermal energy in the PCM and heat the cooking pot. Parameters like solar radiation, humidity, cooker orientation, and ambient temperature were evaluated. The study shows this system can effectively cook and heat food under high altitude conditions with partial cloud cover and moderate
The document presents the results of an experimental analysis of a flat plate solar collector with an integrated latent heat storage unit using phase change material (PCM). Tests were conducted over 60 days from October 2016 to March 2017 in Colombia. The collector reached an average thermal efficiency of 24.11% and a maximum outlet temperature of 50°C. While the PCM provided stability to outlet temperatures during cloudiness, it was unable to supply thermal energy after sunset likely due to a short charging time where the absorber plate temperature reached the PCM melting point. Using a PCM with a lower melting point may increase charging time and improve performance.
IRJET- Efficiency Improvement and Performance Analysis of Solar Collector...IRJET Journal
This document discusses using nanofluids to improve the efficiency of solar collectors. It summarizes the design and fabrication of a flat plate solar collector that uses different shaped copper tubes (circular, triangular, square) as absorber tubes. A computational fluid dynamics (CFD) simulation was performed and results were validated through experimentation on a fabricated solar collector setup. The goal was to increase collector efficiency by changing the absorber tube geometry to increase surface area for heat transfer.
This document discusses thermoacoustics, which uses thermal energy to generate or amplify sound waves. It describes how sound waves can be amplified through heat and used to drive a piston. The key components of thermoacoustic systems are the driver, resonator, stack, and heat exchangers. The resonator contains gas that undergoes compression and cooling from the sound waves. The stack facilitates heat transfer through many small parallel channels. Thermoacoustic systems can be used for refrigeration and have benefits like being environmentally friendly.
This document discusses thermoacoustic engines (TAEs). TAEs use sound waves to pump heat from one place to another, or use a heat difference to induce sound waves. They have no moving parts, making them reliable with a long lifespan. The document outlines the history and discovery of TAEs. It describes the thermodynamic cycle and types of TAEs, including standing wave and traveling wave systems. Components like the heat exchanger, resonator, stack, and regenerator are also explained. The performance, advantages of no moving parts and environmental friendliness, and limitations like low power density of TAEs are summarized.
This document summarizes solar energy utilization in India and types of solar collectors. It discusses that India has high solar potential with about 300 sunny days per year. The key types of solar collectors are flat plate collectors and focusing collectors. It also reviews various artificial roughness geometries that can be used to enhance heat transfer in solar air heaters, such as transverse ribs, V-shaped ribs, and dimples. Experimental studies on single and double pass solar air heaters with different rib configurations are presented.
The document describes two solar powered liquid desiccant cooling systems. The first system was constructed by K. Gommed et al to air condition offices in Haifa, Israel using lithium chloride (LiCl) solution. It achieved a thermal COP of around 0.8 and removed 16 kW of latent heat on average. The second system, studied by Rajat Subhra Das et al for tropical climates like Delhi, India, used LiCl solution and various heat exchangers. It achieved a maximum moisture removal rate of 1.6 g/s and a COP between 0.4-0.8 depending on ambient conditions, with higher COP and capacity at higher ambient humidity levels. Both systems demonstrated the viability of solar
Aia Csi Transpired Solar Collector June2007Sunreps
This document provides information on transpired solar collectors for fresh air heating systems. It discusses how transpired solar collectors work, capturing solar energy through perforated panels to preheat outdoor air drawn into buildings. It outlines key factors to consider for solar collector performance like orientation, climate, solar absorptivity, available solar radiation, ventilation requirements, collector wall area, and air flow rate. The document also notes benefits of these systems for both heating and cooling seasons.
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.
Review of magnetic refrigeration system as alternative to conventional refrig...Naji Abdullah
The refrigeration system is one of the most important systems in industry.
Developers are constantly seeking for how to avoid the damage to the environment. Magnetic
refrigeration is an emerging, environment-friendly technology based on a magnetic solid that
acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials,
MCE warms as the magnetic moments of the atom are aligned by the application of a magnetic
field. There are two types of magnetic phase changes that may occur at the Curie point: first
order magnetic transition (FOMT) and second order magnetic transition (SOMT). The
reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle),
where the magnetic material matrix works both as a refrigerating medium and as a heat
regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer
medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating
fashion through the regenerator made of magnetocaloric material that is alternately magnetized
and demagnetized. Many magnetic refrigeration prototypes with different designs and software
models have been built in different parts of the world. In this paper, the authors try to shed
light on the magnetic refrigeration and show its effectiveness compared with conventional
refrigeration methods.
DESIGN, SIMULATION AND ANALYSIS OF A HYBRID-TYPE (PV/T) SOLAR AIR HEATER FOR ...ijiert bestjournal
This paper deals with the numerical analysis of a H ybrid-Type (PV/T) Solar Air Heater and a study on t he effect of various design parameters that enhance th e performance of the system. The heat transfer improvement in general may be achieved by increasin g the heat transfer coefficient or by increasing th e surface area or by increasing both. The main object ive of the present work is to determine the optimum air mass flow rate at which PV/T systems are to be oper ated and to develop an optimal design of a hybrid t ype (PV/T) solar air heater that shows better performan ce at various heat fluxes due to solar radiation. T his study determines the set of design parameters which lead to the best annual yield of the system. In th is study of a hybrid type (PV/T) solar air heater ICEM CFD (ANSYS) is used to obtain the optimum results,there by increasing the efficiency of the system.
This document summarizes a study that developed a calculation technique to determine the optimal size of flat panel solar thermoelectric systems for combined heat and power production. The technique directly calculates the heat and electric power output based on system parameters like solar irradiation, thermoelectric generator size, and temperatures. The technique was validated through experiments with five commercial thermoelectric generators of varying sizes. Both the calculated and measured results showed there is an optimum system size that achieves maximum heat and electric power output, demonstrating the effectiveness of the developed calculation technique.
International Journal of Computational Engineering Research(IJCER) ijceronline
nternational Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
Thermo acoustic refrigeration uses high intensity sound waves in a pressurized gas tube to pump heat from one place to another and produce a refrigeration effect without lubricants, resulting in 40% less energy consumption. It takes advantage of sound waves reverberating within devices to convert a temperature differential into mechanical energy or vice versa. Applications include liquefying natural gas, chip cooling, refrigerating food, and air conditioning buildings.
A Detailed Review on Artificial Roughness Geometries for Optimizing Thermo-Hy...IJMER
It is well known fact that the heat transfer coefficient between the absorber surface of solar air collector & flowing fluid i.e. air can be improved by providing artificial roughness geometry on heat transfer surface (absorber surface).In this way the Thermal efficiency is increased. But at the same time due to roughness geometry pumping power of solar air collector in increased due to fictional losses in duct. So it necessary to examine the shape, size & flow pattern of various roughness elements to get maximum efficiency with minimum frictional losses. Therefore the selection of roughness geometry has to be based on the parameter that takes into account both Thermal & Hydraulic (friction) performance i.e. Thermo-hydraulic Performance of Solar air collector. Number of roughness elements has been investigated on heat transfer & friction characteristics of solar air collectors. In this paper, reviews of various artificial roughness elements used as passive heat transfer techniques, in order to improve Thermo-hydraulic performance of solar air collectors is reviewed & presented. Correlations developed by various researchers with the help of experimental results for heat transfer & friction factor for solar air collector by taking different roughness geometries are given & these correlations are useful to predict the Thermo-hydraulic performance of solar air collector having roughened ducts. The objective of this paper is also the awareness of effect of various types’ roughness geometries on heat
This document summarizes a research article that developed a simulation application to optimize the position and number of solar collectors in an array to maximize annual energy gain and thermal efficiency. The article describes analyzing a solar collector array system in Macedonia with collectors at different tilts, orientations, and hydraulic connections. It developed a simulation program using the INSEL programming language to perform parametric runs and optimization. Two scenarios were compared: changing the tilt of southeast oriented collectors from 35 to 25 degrees, and retaining the existing 35 degree tilt but adding more collectors. Scenario 1 resulted in over 13% more annual energy gain, while Scenario 2 had 2% higher thermal efficiency.
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.
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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.
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Baraka Zebedayo holds an MBA and BSc in agriculture and has over 10 years of experience managing private sector development projects in Tanzania. He has extensive experience engaging and supporting private sector actors across sectors like dairy, poultry, and agriculture. Currently he is the Private Sector Engagement Manager for Land O'Lakes in Tanzania and Ethiopia, where he is responsible for attracting private sector investments and providing business support. He is seeking new opportunities to advance economic empowerment initiatives through senior strategic roles.
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Against a backdrop of our world’s changing climate solar thermal power generation shows great potential to move global energy production away from fossil fuels to non-polluting sources. A parameter study was conducted based on the previous analysis to improve specific aspects of the initial design using a value of benefit analysis to evaluate the different design. This project focused on the design, analysis and verification of a high temperature solar receiver. Computational Fluid Dynamic (CFD) analysis of Radiation model is carried out with new geometry design of receiver. Discrete Transfer Radiation Model (DTRM) model is used for numerical simulation.
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This document discusses various types of solar thermal energy collectors. It begins by introducing flat-plate collectors that can provide moderate temperatures up to 100°C and are suitable for applications like water heating. It then describes concentrating collectors like parabolic troughs, Fresnel reflectors, and central receiver systems that can achieve higher temperatures by focusing sunlight onto receivers. These higher temperatures make them suitable for electricity generation. The document provides details on the design and operation of each type of collector.
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The document summarizes research on improving the efficiency of flat plate solar collectors through various concentration techniques. It discusses the limitations of conventional flat plate collectors and reviews studies that have incorporated things like twisted wire coils inside tubes, double glazing, selective coatings including nanoparticles, and optical lenses to increase absorption. Experimental results showed efficiency increases ranging from 5% to 15% compared to standard flat plate collectors without these enhancements. The review concludes that ongoing developments aim to make flat plate collectors more compact and effective through improved materials and designs.
The document summarizes key aspects of concentrating solar collectors, including:
1) Concentrating collectors can achieve higher temperatures than flat plate collectors by optically focusing sunlight onto a small receiver area. Common types include parabolic troughs, dishes, and power towers.
2) Concentration ratios refer to the ratio of aperture area to receiver area, with practical maximums of 200 for point focus systems and 80 for linear focus collectors.
3) Higher temperatures allow applications like power generation but require tracking the sun and more complex designs. Optical and thermal performance factors determine collector efficiency.
The document summarizes different types of concentrating solar collectors, including parabolic troughs, dishes, power towers, and Fresnel lenses. It describes the key features and working principles of each technology. Parabolic troughs use linear reflectors to concentrate sunlight onto receiver tubes, achieving temperatures up to 400°C. Power towers use an array of tracking mirrors to focus sunlight onto a central receiver atop a tower, allowing temperatures over 550°C. Concentrating collectors can achieve higher temperatures than flat plates, making them suitable for industrial heat and power applications.
This document describes the design of six simple solar water heating systems suitable for use in Basra, Iraq. The systems are designed to be inexpensive and easy to build using locally available materials. The six designs include a basic galvanized iron tube collector, and designs that add features like a wooden insulation box, black paint coating, a copper plate reflector, aluminum sheet insulation, and a double tube collector. Experimental testing showed that the designs were able to heat water to temperatures over 90°C even on cold winter days in Basra. The theoretical model developed to analyze the systems showed good agreement with experimental data.
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This document describes an experimental setup for a solar vapor absorption cooling system using a flat plate collector. The system consists of two main circuits: 1) A solar water heating system circuit that uses a flat plate collector to heat water which is then used in the generator. 2) A vapor absorption refrigeration circuit consisting of a generator, absorber, evaporator, condenser and solution heat exchanger, using an ammonia-water working fluid. Experimental results showed a temperature drop of 7-8°C in the evaporator and a coefficient of performance of 0.75-0.79 for the solar powered vapor absorption system, lower than the maximum theoretical COP of 3.11 but demonstrating the potential to produce refrigeration from solar energy
This document discusses a system designed to increase the efficiency of concentrated solar power generation. The system uses a parabolic trough solar concentrator and heat exchanger to capture waste heat from a solar panel. By focusing sunlight and transferring heat to a working fluid, the system aims to utilize more of the solar energy than traditional photovoltaic panels alone. An experiment will track system temperatures and solar input to calculate the overall efficiency gained from combining thermal and electrical energy collection. The results could demonstrate a six-fold increase in energy captured through cogeneration compared to photovoltaics alone.
EXPERIMENTAL STUDY ON SOLAR HEATING BY NATURAL HEAT CONVECTION AND RADIATIONADEIJ Journal
Heat storage is a good energy saving option these days. Heat storage makes it possible to use thermal
energy at the required time. Solar water heaters for construction purposes and industrial purposes are the
best source to maintain traditional energy sources and thus can maintain high quality energy and liquid or
steel fuel due to the highest rise in their prices. In recent years, using solar energy has become remarkably
cheap and especially noteworthy. The efficiency of natural solar water heater system depends on collector
and reservoir setting, design and environmental factors such as solar intensity, ambient temperature and
wind conditions. Also, the relative height of the tank and collector separation mainly affects the volume of
the Siphon thermal flow rates, including both forward and reverse flow at night. In this pilot investigation,
two parallel rectangular glass plates were connected to the hot water storage tank. The effect of the
separation space between the plates (collectors) (D) was investigated and reported. The results reported
that outlet temperature in case D= 15 cm for two plates decreased approximately 24% and 23% for two
plates. Also, the heat radiated to the room decreased as the inner space between the two plates increased,
and decreased to approximately 25% as compared to stack plates.
The document discusses different types of solar collectors and components of flat plate collectors. Flat plate collectors consist of an absorber plate, glass cover, insulation, and enclosure. They work by absorbing solar radiation to heat a fluid flowing through tubes attached to the absorber plate. The performance of collectors is determined by measuring the inlet and outlet fluid temperatures and flow rate. Collector efficiency is the ratio of useful energy gain to incident solar energy. Temperature distributions in collectors and methods for calculating overall heat loss coefficients are also examined.
A Thesis on Design Optimization of Heat Sink in Power ElectronicsIJERA Editor
The heat sinks are used in electronic systems to remove heat from the chip and effectively transfer it to the ambient. The heat sink geometry is designed by the mechanical engineers with the primary aim of reducing the thermal resistance of the heat sink for better cooling in the electronic systems. Due to the proximity of the heat sink with the ICs, the RF fields created by RF currents in the ICs/PCBs gets coupled to heat sinks. Hence, the coupled RF current can cause radiated emission. This radiated noise from the device can couple and disturb the functioning of the nearby electronic systems. Also this radiated emission from the device poses a problem to the system compliance with respect to EMI/EMC regulations. The international EMI/EMC standards require the radiated emission from the electronic devices to be kept below the specified limits. As a result the design of Heat Sink is very important factor for the efficient operation of the electronic equipment. In this project design optimization of a Heat sink in a Power amplifier is performed to reduce the weight and size .Power amplifier is electronic equipment mounted in an army vehicle. The power modules inside the amplifier generates a heat of 1440 Watts and a temperature of 140 0c.Two Heat sinks are used to dissipate the heat generated inside the equipment and maintain a temperature of less than 850c. The existing heat sink which is being used is weighing around 10.3kgs and height of 51mm; as a result the unit is very robust. The objective of my project is To design & optimize the heat sink to reduce the weight and size. The optimized heat sink should also dissipate heat generated by power modules and maintain a temperature of less than 850c inside. To achieve the design a steady state thermal analysis will be performed on the heat sink and plot the Temperature distribution on the fins. Based on the above analysis results we will increase/decrease the number of fins, thickness of fins, and height of fins to reduce the weight of the heat sink. We will perform CFD analysis of the power amplifier by mounting the optimized heat sink and plot temperature, pressure and velocity distribution in the power amplifier enclosure. Efforts are made to optimize temperature, pressure and velocity distribution in the power amplifier enclosure by reorienting the power modules in the enclosure. UNIGRAPHICS software is used for 3D modeling SOLID WORKS FLOW SIMULATION software is used for thermal and CFD analysis.
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Absorber Technology for Concentrated Solar Power System
1. Page 1
Analysis of the Thermal Losses in the Innovative
Technology, the Compact Fresnel Linear Reflector with the
trapezoidal absorbers.
Capstone Research Course (E 194)
Name: Fang-Ming Lin
Department of Engineering Science
Major: Energy Engineering
Course supervisor: Van Carey
Department of Mechanical Engineering
Abstract
Concentrated Solar Power System (CSP) is the most proven technology for the solar energy
technology. The compact Fresnel Linear Reflector takes the concept of trough design and
enhance the efficiency and reduce the cost with a set of rows, flattening the parabolic
reflectors into flat mirrors. With this change, the mirrors are able to avoid the thermal oil used
in traditional receiver technology, the concentrated sun light is then used directly to heat
water, produce the superheated steam and improve the thermal efficiency. Since the efficiency
for the solar power system is extremely important, it would be analyzed through the heat loss
happens at the light absorber, with the adjusting cavity angles cavity depth and the insulation
thickness, heat loss would be analyzed for obtaining the most efficient configuration for the
technology of CSP.
2. Page 2
1. INTRODUCTION
1.1 The Compact Fresnel Linear Reflector
Concentrated solar power (CSP) is one of the most important candidate for providing the
majority of the energy source because of its cost-effective electricity technologies and its
potential for further technology improvements. The Compact Fresnel Linear Reflector is the
innovative design which is suitable for the large-scale solar thermal energy collection but also
efficiently uses the available power plant area, further reducing the cost with the low-cost
materials([3] Edkins et al). In traditional Fresnel Linear Reflector, there is only one absorber,
reflectors concentrate the sun light all to the only one linear system. For this design, it contains
many optical losses, especially the shading loss, with its geometric configuration that produces
the limits. With the Compact Fresnel Linear Reflector, its design system contains at least two
absorbers, which absorbs reflected sun light from a series of mirror that are put into different
configuration, the mirrors placed on the outside of the two absorbers maintain the same
configuration as the traditional Fresnel Linear Reflector, but for the mirrors sit between two
absorbers, each mirror faces to the opposite direction as to the adjacent one so that it reduces
the shading loss and enhance the optical efficiency ([10] Pye, John D et al).
1.2 Direct Steam Generation
For most of the innovative design of the Compact Fresnel Linear Reflector, it uses the
technology of direct steam generation to do the heat conversion. The basic idea of the Direct
Steam Generation is heating the water directly and generating steam from it without going
through from various energy mechanisms and transitions. Unlike the most common chosen
heat transfer fluids (HTF), the synthetic thermal oil or the molten salt; the direct steam
generation uses water as the heat transfer fluid and directly generates the steam with a more
simplified model by eliminating the complex heat exchanger component. With the usage of the
synthetic thermal oil or the molten salt, the maximum temperature the system can reach is
around 400 Celsius. With the application of direct steam generation, it is able to exceed the
limited temperature and reaches up to 550 Celsius ([1] Alguacil, M. et al). With this, the direct
steam generation enhances the efficiency by increasing the steam temperature, and avoids the
environmental risk that the traditional HTF can have.
2. DATA COLLECTION
2.1 Heat Transfer and Heat Loss on the Receiver
For the solar power collectors, each collector contains a concentrator and a receiver.
Two main types of concentrators are the nonimaging concentrator or the focusing
concentrator, and the two main types of receivers are the refracting lens type or the reflecting
mirror type. Therefore the performance for each solar collector is determined by two
parameter, the concentration and the acceptance angle ([14] Vieira, 2005).
3. Page 3
In order to analyze the heat transfer and heat loss, the design of the receiver is really
important, different factors will result in different effects on each design. The choice of the type
of receiver the concentrated power system was made of would determine the analysis for the
heat loss. There are two types of receiver designs, which later receiver designs deviate from
them but still sustain those fundamental concepts from the formers. These two types are the
Heat Loss from Linear, Omnidirectional Receiver and the Heat Loss from Cavity Receiver.
Furthermore, sizing the receiver will also alter different heat loss for the receiver, finding the
optimal receiver size is crucial to the design of the receiver. ([13] Stine, William B. et al). The
fundamental calculation is conducted by including the heat loss through convection and the
heat loss through the radiation:
𝑄𝑙𝑜𝑠𝑠,𝑔
̇ = ℎ 𝑔 𝐴 𝑔(𝑇𝑔 − 𝑇𝑎) + 𝜎 𝐵 𝜖 𝑔 𝐹𝑔 𝑎 𝐴 𝑔(𝑇𝑔
4
− 𝑇𝑠
4
) 𝐿𝑖𝑛𝑒𝑎𝑟, 𝑂𝑚𝑛𝑖𝑑𝑖𝑟𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟𝑠
𝑄𝑙𝑜𝑠𝑠,𝑐𝑎𝑣
̇ = ℎ 𝑐𝑎𝑣 𝐴 𝑐𝑎𝑣(𝑇𝑐𝑎𝑣 − 𝑇𝑎) + 𝜎 𝐵 𝜖 𝑐𝑎𝑣 𝐹𝑐𝑎𝑣 𝐴 𝑐𝑎𝑣(𝑇𝑐𝑎𝑣
4
− 𝑇𝑠
4) 𝐶𝑎𝑣𝑖𝑡𝑦 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟𝑠
In this paper, since the focus is on the Compact Linear Fresnel Reflector, the heat loss
analysis would deviate from the fundamental ones, and follows the experimental model
performed by Reynolds and Jance at University of New South Wales ([6] Jance et al, 2000) and
later the calculation introduced by Pye from the same school ([9] Pye et al, 2003).
Instead of using a flat plate absorber, this model of Compact Linear Fresnel Reflector
uses the multi-tube solar collector structure that within the trapezoid absorber, there are
several numbers of the cylindrical absorber side-by-side arranged with each other. Since the
concentrator is the ratio of the aperture area to the receiver area, by decreasing the area of the
receiver, the concentrator is improved. ([8] Lievre, 2011)
The material chosen for the trapezoid absorber is aluminum. “A significant benefit of
aluminum and the aluminum extrusion process is the almost unlimited opportunity to adapt
the shape of the product to optimize performance, maximize stiffness and strength, and reduce
the number of parts to assemble and fabricate; all of which contribute to lowering cost” ([4]
Hydro Solar Solutions). If we were to find the temperature difference between the aluminum
wall and the surrounding temperature, we applied the Wiedemann-Franz law, k =
Lo 𝑇
𝜌
, where Lothe Lorenz number(2.45 × 10−8
𝑊 ∙ Ω ∙ 𝐾−2
). ([15] Woodcraft, 2005)
The model developed for this trapezoid absorber contains more parameters in order to
calculate the heat loss corresponding to its dimensions to the functions of the cavity depth or
he absorber temperature ([9] Pye et al, 2003). There are two parts of heat loss analysis, the
heat loss for the absorber and the heat loss for the cavity. Deriving from the fundamental heat
loss equation, the heat loss for absorber through radiation is kept the same and for the heat
loss through convection, the Nusselt number (Nu) and the Grashof number (Gr) are used for the
analysis.
𝑄𝑡𝑜𝑡𝑎𝑙 = 𝑄 𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛 + 𝑄 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛
4. Page 4
Where radiative heat lows is:
𝑄 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 = 𝐹𝑟𝑎𝑑 𝜎𝜖 𝑎(𝑇𝑎
4
− 𝑇𝑔
4
), 𝑤ℎ𝑒𝑟𝑒 𝐹𝑟𝑎𝑑 = 0.90
And here shows the relationship between Nu, Gr numbers, and the convective heat loss:
𝑁𝑢 =
𝑄 𝑐𝑜𝑣
𝑊
(
𝑘 𝑐
𝐷
) (𝑇𝑔 − 𝑇𝑎)
𝑁𝑢 = 1.1917𝐺𝑟0.10363
(
𝐷
𝑊
)
0.6432
𝐺𝑟 =
9.8𝛽𝑐(𝑇𝑎 − 𝑇𝑔)𝐷3
𝑣𝑐
2
, 𝑤ℎ𝑒𝑟𝑒 𝛽𝑐 𝑎𝑛𝑑 𝑣𝑐 𝑜𝑏𝑡𝑎𝑖𝑛𝑒𝑑 𝑓𝑟𝑜𝑚 𝑇𝑐 =
1
2
(𝑇𝑎 + 𝑇𝑔)
The heat loss for the cavity for the cavity from the cavity is much simpler but unlike the
heat loss for the absorber that only convection heat loss is geometrically dependent, the
radiation heat loss for the cavity also depends on the width of the window. The equations are
given for the heat loss of convection at two sides of the walls and at the window, and the
radiation heat loss at the window:
𝑄 𝑤,𝑐𝑜𝑛𝑣 = 𝑁ℎ 𝑤(𝑇𝑐 − 𝑇𝑒) (𝐶𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛 ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 𝑎𝑡 𝑡ℎ𝑒 𝑤𝑎𝑙𝑙)
𝑄 𝑔,𝑐𝑜𝑛𝑣 = 𝐵ℎ 𝑤(𝑇𝑔 − 𝑇𝑒) (𝐶𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛 ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 𝑎𝑡 𝑡ℎ𝑒 𝑤𝑖𝑛𝑑𝑜𝑤)
𝑄 𝑔,𝑟𝑎𝑑 = 𝐵𝜖 𝑔 𝜎(𝑇𝑔
4
− 𝑇𝑒
4
) (𝑅𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 𝑎𝑡 𝑡ℎ𝑒 𝑤𝑖𝑛𝑑𝑜𝑤)
Here we notice that the radiation heat loss for the cavity does not include the Radiation
shape factor,𝐹𝑟𝑎𝑑, this is because the B, the width of the window has already taken the
geometrical consideration into account.
2.2 Analytic calculation
In this paper, instead of general heat loss computation, the approach to analyze the
heat loss is applying the most fundamental analogy, the Thermal Resistance Circuits. Here, a
brief introduction will be given. ([5] Incropera, Frank P)
From Ohm’s law
E! − 𝐸2
𝐼
=
𝐿
𝜎𝐴
We know that heat transfer by conduction is
5. Page 5
Qcond =
kA(T2 − 𝑇1)
𝐿
𝑤ℎ𝑒𝑟𝑒 𝑇2 𝑖𝑠 𝑡ℎ𝑒 ℎ𝑖𝑔ℎ 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒, 𝑎𝑛𝑑 𝑇1 𝑖𝑠 𝑡ℎ𝑒 𝑙𝑜𝑤 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
Qconv = hA(Tw − 𝑇∞)
𝑤ℎ𝑒𝑟𝑒 𝑇 𝑤 𝑖𝑠 𝑡ℎ𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑎𝑡 𝑡ℎ𝑒 𝑜𝑏𝑗𝑒𝑐𝑡
𝑎𝑛𝑑 𝑇∞ 𝑖𝑠 𝑡ℎ𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑢𝑡𝑒 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑠𝑢𝑟𝑟𝑜𝑢𝑛𝑑𝑖𝑛𝑔 𝑎𝑖𝑟 𝑜𝑟 𝑡ℎ𝑒 𝑔𝑎𝑠
When we replace the voltage drop with the temperature difference, and after the thermal
resistance circuit is arranged, the thermal resistance becomes
Rcond =
(T2 − 𝑇1)
𝑞
=
𝐿
𝑘𝐴
Rconv =
(T 𝑤 − 𝑇∞)
𝑞
=
1
ℎ𝐴
In this paper, it would be separated into two sections of resistance analysis. The first
section would be included with the hottest region, where the absorber tubes locate. The
second region would be included with the enclosed convection coefficient. We would make an
assumption that the temperature at the absorber region is 100 degree Celsius higher than the
average temperature enclosed in the absorber cavity.
Figure 1. Cross section of the absorber view
(with 0.5m length of the absorber shown), created by [12] SolidWorks
6. Page 6
Figure 2. Thermal resistances for the solar absorber cavity, created by [2] AutoCAD
First, with the sketch provided above, we know that for the top of the cavity, the
thermal resistance analysis consists of the insulation resistance, which would be represented by
the inverse of thermal conductance times the thickness of the insulation. This would then in
series with the convection inside the cavity, the convection coefficient here would depend on
the height of the absorber. Lastly, the resistance of the convection and radiation from the
absorber wall to the surrounding will also be included in the analysis. The thermal resistance
equations for the top side of cavity is:
𝑅𝑡𝑜𝑝 = 𝑅 𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛,𝑒𝑛𝑐𝑙𝑜𝑠𝑢𝑟𝑒 + 𝑅𝑖𝑛𝑠𝑢𝑙𝑎𝑡𝑒𝑑 + 𝑅 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑,𝑠𝑢𝑟𝑟
, 𝑅 𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛,𝑒𝑛𝑐𝑙𝑜𝑠𝑢𝑟𝑒 =
1
ℎ 𝑐𝑎𝑣𝑖𝑡𝑦 𝐴 𝑡𝑜𝑝
, 𝑤ℎ𝑒𝑟𝑒 ℎ 𝑐𝑎𝑣𝑖𝑡𝑦 =
𝑘 𝑎𝑖𝑟
𝐷/2
𝑅𝑖𝑛𝑠𝑢𝑙𝑎𝑡𝑒𝑑 =
𝑡𝑖𝑛𝑠𝑢𝑙𝑎𝑡𝑒𝑑
𝑘𝑖𝑛𝑠𝑢𝑙𝑎𝑡𝑒𝑑
𝑎𝑛𝑑 𝑅 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑,𝑠𝑢𝑟𝑟 =
1
ℎ 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 𝐴 𝑡𝑜𝑝
, 𝑤ℎ𝑒𝑟𝑒 ℎ 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 = ℎ 𝑤 + ℎ 𝑟𝑎𝑑 , 𝑎𝑛𝑑 ℎ 𝑔 = 4 × εg × σ × Frad ∗ 𝑇 𝑚
3
, 𝑇 𝑚 =
𝑇𝑎 + 𝑇𝑔
2
, 𝑇𝑎 𝑟𝑒𝑝𝑟𝑒𝑠𝑒𝑛𝑡𝑠 𝑡ℎ𝑒 ℎ𝑜𝑡 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑟𝑒𝑔𝑖𝑜𝑛
, 𝑤ℎ𝑖𝑐ℎ 𝑖𝑠 𝑡ℎ𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑤𝑖𝑡ℎ𝑖𝑛 𝑡ℎ𝑒 𝑐𝑎𝑣𝑖𝑡𝑦 𝑜𝑟 𝑎𝑟𝑜𝑢𝑛𝑑 𝑡ℎ𝑒 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑟
, 𝑇𝑔 𝑟𝑒𝑝𝑟𝑒𝑠𝑒𝑛𝑡𝑠 𝑡ℎ𝑒 𝑐𝑜𝑙𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑟𝑒𝑔𝑖𝑜𝑛, 𝑤ℎ𝑖𝑐ℎ 𝑖𝑠 𝑡ℎ𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑢𝑡𝑠𝑖𝑑𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑎𝑣𝑖𝑡𝑦
For the sides’ walls the heat loss comes from the combined heat loss of radiation and
convection, the conduction heat loss at the wall, and also the radiation and convection heat
loss to the surrounding. The thermal resistance equations in this case would be,
Rwall = Rconvection,enclosure + Rcond,wall + 𝑅 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑,𝑠𝑢𝑟𝑟, where Rcond,wall =
L
𝑘𝐴 𝑤𝑎𝑙𝑙
and Rconvection,enclosure ℎ𝑎𝑠 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑒𝑞𝑢𝑎𝑡𝑖𝑜𝑛 𝑎𝑠 𝑡ℎ𝑒 𝑜𝑛𝑒 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑡𝑜𝑝 𝑠𝑖𝑑𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑎𝑣𝑖𝑡𝑦
7. Page 7
, 𝑎𝑛𝑑 𝑠𝑜 𝑑𝑜𝑒𝑠 𝑡ℎ𝑒 ℎ 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑣𝑒 𝑟𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒.
Lastly, for the heat loss analysis at the glass side, the heat loss is the same as the sides’
walls, except the thermal conductivity and the thickness of the glass are different, which the
heat loss from conduction would be different. However, another assumption would be made
here is that we would neglect the thickness of the glass window. Therefore, the equations for
the thermal resistance is:
Rglass = Rconvection,enclosure + 𝑅 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑,𝑠𝑢𝑟𝑟
In order to find the final total heat loss, besides the series thermal resistance analysis
we did on the top side of the solar absorber, we would also do a parallel analysis on the glass
side and the wall sides. Furthermore, here we notice that the absorber is geometrically
symmetric, 𝑅 𝑠𝑖𝑑𝑒 can then be doubled to represents both sides of the absorber walls.
Therefore, the parallel resistance will become:
𝑅 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙 = (
1
Rglas
+
1
2 × 𝑅 𝑠𝑖𝑑𝑒
)
−1
𝑎𝑛𝑑 𝑡ℎ𝑒 ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 ℎ𝑒𝑟𝑒 𝑤𝑜𝑢𝑙𝑑 𝑏𝑒:
𝐻𝑒𝑎𝑡 𝐿𝑜𝑠𝑠, 𝑄ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠_𝑏𝑜𝑡𝑡𝑜𝑚 =
(𝑇𝑒𝑛𝑐𝑙𝑜𝑠𝑒𝑑 − 𝑇𝑠𝑢𝑟𝑟)
𝑅 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙
With the heat loss obtained earlier from the absorber’s top side,
, ℎ𝑒𝑟𝑒 𝑡ℎ𝑒 ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 𝑤𝑜𝑢𝑙𝑑 𝑏𝑒 𝑄ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠_𝑡𝑜𝑝 =
𝑇𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑟 − 𝑇𝑠𝑢𝑟𝑟
𝑅𝑡𝑜𝑝
The total heat loss would be 𝑄ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠_𝑡𝑜𝑡𝑎𝑙 = 𝑄ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠_𝑡𝑜𝑝 + 𝑄ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑠_𝑏𝑜𝑡𝑡𝑜𝑚
Now the analysis would be emphasized on changing three variables with two varying
bases. The two varying bases are the temperature outside of the absorber cavity (𝑇𝑔) and the
temperature inside of the cavity (𝑇𝑎). The three parameters will be changed are the depth of
the absorber, the angle of the absorber inclination, and the thickness of the insulation. We
would analyze the changes for the total heat loss after each adjustment. When one parameter
is changing, the other two parameters would be set to the middle values, such as when we are
changing the depth of the absorber from 50mm, 100mm, 150mm, the values used for the
inclination angle and the 45⁰, and 20mm.
8. Page 8
2.3 Graphical results
2.3.1 Adjustments on the depth of the absorber
Figure 3. Heat Loss with D=0.05m, θ=45⁰, t=0.02m
Figure 4. Heat Loss with D=0.1m, θ=45⁰, t=0.02m
Figure 5. Heat Loss with D=0.15m, θ=45⁰, t=0.02m
9. Page 9
2.3.2 Adjustments on the inclination angle of the absorber
Figure 6. Heat Loss with D=0.1m, θ=30⁰, t=0.02m
Figure 7. Heat Loss with D=0.1m, θ=45⁰, t=0.02m
Figure 8. Heat Loss with D=0.1m, θ=60⁰, t=0.02m
10. Page 10
2.3.3 Adjustments on the thickness of the insulation
Figure 9. Heat Loss with D=0.1m, θ=45⁰, t=0.0m
Figure 10. Heat Loss with D=0.1m, θ=45⁰, t=0.02m
Figure 11. Heat Loss with D=0.1m, θ=45⁰, t=0.05m
11. Page 11
3. DISCUSSION AND CONCLUSION
3.1 Discussion
First, from figure 3, figure 4, and figure 5 above, we notice that the higher the depth,
the less the heat loss is. Secondly, from figure 6, figure 7, and figure 8, the plots show us that
the smaller angle is, the more the heat loss is. These two sets of plots agree with each other
that more space for the internal side of the absorber reduces the heat loss, since that the
absorber can enclose more warm air within the cavity. Another set of plots, figure 9, figure 10,
and figure 11 show that the thickness of insulation also have huge impact on the heat loss. The
insulating material is meant to enclose the heat inside the cavity and prevent the heat from
losing. These three graphs prove the prediction that the heat loss decreases as the thickness of
the insulation is increased.
Since all the previous plots showed each different case for a given x-axis and y-axis, the
following plots compare the heat loss for all different 7 cases at a given surrounding
temperature. It is clear to see from the figure 12 that when the surrounding temperature is
lower (here Temperature = 373 K is chosen), the heat enters into the cavity is less hence the
overall heat loss is less. The high surrounding temperature chosen for comparing is shown in
the figure 13 that when the surrounding temperature is 673 K, the overall heat loss increases.
Figure 12. Heat loss for seven combinations at temperature = 373 (K)
12. Page 12
Figure 13. Heat loss for seven combinations at temperature = 673 (K)
It is interesting to observe from the results that the combinations, [0.1, 30, 0.02], [0.1,
45, 0.0], and [0.05, 45, 0.02] (the depth of the absorber, the inclination angle, the thickness of
insulation) have higher heat losses for both surrounding temperatures compared to the other
four combinations. They either have small inclination angle, small insulation thickness, or small
height of the absorber, and these characteristics also agree to the results concluded earlier.
3.2 Conclusion
In this paper, the heat loss for the trapezoid solar absorber used for the Concentrated
Solar Power System is analyzed and the adjustments for the geometry (the height of the
absorber cavity and the inclination angle for the absorber), and the insulation thickness are
made to find the optimal combination for the absorber design.
The conclusion comes that no matter for high or low surrounding temperatures, the
combination for the absorber design should include high cavity depth and larger inclination
angle to make a larger enclosed space. Excluding the material cost for now, the insulation
thickness should be maximized to secure the hot air enclosed within the absorber cavity.
The future work for this project includes analyzing the impact how Direct Steam
Generation would help to reduce the heat loss and maximize the system overall efficiency.
More parameters and tests could be carried out and present another more accurate report, and
to find the best geometric configuration for this concentrated power absorber system.
13. Page 13
4. Appendix
4.1 Constant and varied parameters ([10] Pye, John D et al, [7] Lai, Yanhua et al)
Constant
Parameter
Definition
𝜎 5.6696 × 10−8
𝑊/𝑚2
𝐾4 Stefan-Boltzmann constant
𝜖 𝑡 0.5 Absorber top emissi vity
𝜖 𝑎 0.1 Absorber wall emissivity
𝜖 𝑔 0.85 Glass cover emissivity
𝑘 𝑐 0.58 W/m ∙ 𝐾 Thermal conductivity
ρ 2.65 × 10−8
Ω ∙ 𝑚 Resistivity for aluminum
𝑘 𝑎𝑖𝑟 0.024 W/m ∙ 𝐾 Air conductivity
ℎ 𝑔 2.6 W/m2
∙ 𝐾
Convection coefficient outside of the cavity
window (glass side)
ℎ 𝑤 0.5 W/m2
∙ 𝐾
External heat loss coefficient outside of cavity
side walls
L 60 m Length of the absorber
W 160 mm Width of the receiver
T 20 mm The thickness of the wall
𝑘𝑖 0.04 W/m ∙ 𝐾 Insulation thermal conductivity
Varied
Parameter
Definition
D 50,100,150 (mm) Depth of the absorber
ℎ 𝑤
kair
𝐷/2
Convection coefficient inside of the cavity
t 0, 20, 50 mm The thickness of the insulation
𝜃 30,45,60 (°) Inclination of the wall
𝑇𝑎 100,200,300,400 (℃) Temperature enclosed in the absorber
𝑇𝑔 270,280,290,300,310 (K)
Temperature at the outside surface of the
absorber
15. Page 15
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