The document discusses cryogenics and its applications. It provides details about a thermal heat switch developed for cryogenic space applications operating near 100 K. The switch uses the difference in linear thermal expansion coefficients of materials to operate. It was designed to separate two pulse tube cold heads cooling a common focal plane array. Testing showed the switch reliably changed states around 220 K with adequate on/off conductivity. Long-term creep testing of the thermoplastic material used found up to 12% reduction in contact pressure after 10 years at 100 K. The switch concept shows promise for redundant cryocooler applications in space.
This document discusses cryogenics and cryogenic materials. It begins with an introduction defining cryogenics as the study of materials at temperatures below -150°C and how materials' properties change at cryogenic temperatures. It then discusses various cryogenic materials and their applicable temperature ranges. The document outlines how mechanical and thermal properties such as strength, ductility, and thermal expansion/contraction change at low temperatures. Finally, it briefly discusses applications of cryogenics in aerospace, medicine, manufacturing, and electronics.
This document discusses refrigerant compressors, including their classification and types. It describes reciprocating compressors, which use pistons driven by a crankshaft to compress gases. Rotary compressors are also covered, using two meshing screws to compress gas. Centrifugal compressors rely on the kinetic energy of an impeller to increase pressure. Direct drive and belt drive compressors are compared, as well as hermetic and semi-hermetic compressors, which enclose components within a sealed shell.
This document provides information on various metal rolling processes including hot rolling, cold rolling, and other specialized rolling techniques. It discusses the basic components and setup of rolling mills. Key rolling processes are defined, such as continuous rolling, shaped rolling, and ring rolling. The document also examines the differences between hot and cold rolling, and provides examples of typical rolling mill operations. Mathematical approaches for calculating rolling loads are introduced.
The ppt contains detailed study of Vapor Absorption Refrigeration System with neat sketches and description. It is well formed as per the syllabus of GTU
This document discusses different types of refrigerants including their classification and designation. It covers halo-carbon, hydro-carbon, inorganic, azeotrope, zeotropic, and hydrocarbon refrigerants. It explains that refrigerants are designated with an 'R' followed by numbers that indicate their chemical composition. Common refrigerants like R11, R12, ammonia, and carbon dioxide are discussed along with their substitutes due to environmental concerns.
Forced convection involves an external force moving a fluid over a surface, enhancing heat transfer between the surface and fluid. The rate of heat transfer depends on properties of the fluid and surface, as well as the type of fluid flow. As fluid moves over a surface, velocity and thermal boundary layers form near the surface. For a flat plate, the Nusselt number relationship depends on whether flow is laminar or turbulent. In laminar flow, Nu increases with the 1/2 power of the Reynolds number, while in turbulent flow Nu increases with the 1/4 power of the Reynolds number. These relationships can be used to determine average heat transfer over the plate.
Difference between Pipe and Tube are sometimes confusing, go through this slideshow to understand some basic features of pipes and tubes that make them different from each other
Cryogenics is the study of very low temperatures, including temperatures below -150°C that can be attained using cryogenic liquids like liquid nitrogen and liquid helium stored in Dewar flasks. Some key applications of cryogenics discussed include cryogenic rocket engines, which provide high energy per unit mass and were pioneered by the US and India. Cryogenic grinding is also discussed as an application, which avoids problems with heat generation, tool wear, and oxidation seen in conventional grinding. Both advantages like lower grinding costs and finer particle sizes, and disadvantages like high operating costs are reviewed. Health hazards associated with cryogenic liquids like frostbite and cold embrittlement are also summarized.
This document discusses cryogenics and cryogenic materials. It begins with an introduction defining cryogenics as the study of materials at temperatures below -150°C and how materials' properties change at cryogenic temperatures. It then discusses various cryogenic materials and their applicable temperature ranges. The document outlines how mechanical and thermal properties such as strength, ductility, and thermal expansion/contraction change at low temperatures. Finally, it briefly discusses applications of cryogenics in aerospace, medicine, manufacturing, and electronics.
This document discusses refrigerant compressors, including their classification and types. It describes reciprocating compressors, which use pistons driven by a crankshaft to compress gases. Rotary compressors are also covered, using two meshing screws to compress gas. Centrifugal compressors rely on the kinetic energy of an impeller to increase pressure. Direct drive and belt drive compressors are compared, as well as hermetic and semi-hermetic compressors, which enclose components within a sealed shell.
This document provides information on various metal rolling processes including hot rolling, cold rolling, and other specialized rolling techniques. It discusses the basic components and setup of rolling mills. Key rolling processes are defined, such as continuous rolling, shaped rolling, and ring rolling. The document also examines the differences between hot and cold rolling, and provides examples of typical rolling mill operations. Mathematical approaches for calculating rolling loads are introduced.
The ppt contains detailed study of Vapor Absorption Refrigeration System with neat sketches and description. It is well formed as per the syllabus of GTU
This document discusses different types of refrigerants including their classification and designation. It covers halo-carbon, hydro-carbon, inorganic, azeotrope, zeotropic, and hydrocarbon refrigerants. It explains that refrigerants are designated with an 'R' followed by numbers that indicate their chemical composition. Common refrigerants like R11, R12, ammonia, and carbon dioxide are discussed along with their substitutes due to environmental concerns.
Forced convection involves an external force moving a fluid over a surface, enhancing heat transfer between the surface and fluid. The rate of heat transfer depends on properties of the fluid and surface, as well as the type of fluid flow. As fluid moves over a surface, velocity and thermal boundary layers form near the surface. For a flat plate, the Nusselt number relationship depends on whether flow is laminar or turbulent. In laminar flow, Nu increases with the 1/2 power of the Reynolds number, while in turbulent flow Nu increases with the 1/4 power of the Reynolds number. These relationships can be used to determine average heat transfer over the plate.
Difference between Pipe and Tube are sometimes confusing, go through this slideshow to understand some basic features of pipes and tubes that make them different from each other
Cryogenics is the study of very low temperatures, including temperatures below -150°C that can be attained using cryogenic liquids like liquid nitrogen and liquid helium stored in Dewar flasks. Some key applications of cryogenics discussed include cryogenic rocket engines, which provide high energy per unit mass and were pioneered by the US and India. Cryogenic grinding is also discussed as an application, which avoids problems with heat generation, tool wear, and oxidation seen in conventional grinding. Both advantages like lower grinding costs and finer particle sizes, and disadvantages like high operating costs are reviewed. Health hazards associated with cryogenic liquids like frostbite and cold embrittlement are also summarized.
This document provides an overview of additive manufacturing (AM), also known as 3D printing. It defines AM as a process of joining materials layer by layer to make objects from 3D model data, as opposed to subtractive manufacturing methods. The document discusses different AM technologies including liquid-based, solid-based, powder bed fusion, and binder jetting. It also covers applications of AM in the medical and automotive industries, benefits of AM including design freedom and reduced material waste, and limitations such as part size restrictions.
The actual vapor compression cycle differs from the theoretical cycle in several ways that cause losses. In the actual cycle, the refrigerant leaves the evaporator as superheated vapor, compression is neither isentropic nor polytropic, and the refrigerant enters the expansion valve in a subcooled liquid state. Pressure drops also occur in the evaporator and condenser. Deviations from the theoretical cycle increase the required compressor work and can decrease the coefficient of performance. Changes in suction and discharge pressures also affect the refrigerating capacity and cost.
This document provides information on refrigerants including their definition, history, classification, properties, and environmental impact. It discusses early natural refrigerants and the development of artificial refrigerants over time. Refrigerants are classified based on their working principle and chemical properties. Key criteria for refrigerant selection include thermodynamic properties, environmental and safety factors, and cost. Common synthetic refrigerants discussed are CFCs, HCFCs, HFCs, hydrocarbons, and inorganic refrigerants like ammonia and carbon dioxide.
This document provides an introduction to non-conventional machining processes. It discusses how these processes use indirect energy like sparks, lasers, heat, or chemicals rather than direct contact between a tool and workpiece. Some key non-conventional machining processes described include electrical discharge machining, wire EDM, laser beam machining, electron beam machining, water jet machining, abrasive jet machining, ultrasonic machining, electrochemical machining, and electrochemical grinding. Advantages of these processes include high accuracy, less wear, longer tool life, and reduced environmental hazards compared to conventional machining.
The document discusses various methods of case hardening steel, which involves hardening only the surface layer while leaving the inner core relatively soft. The key methods covered are carburizing (including pack, liquid, and gas carburizing), cyaniding, nitriding, carbonitriding, induction hardening, flame hardening, and vacuum/plasma carburizing. The Jominy end quench test is described as a method to measure the hardenability or hardening depth of steels.
The document discusses refrigeration systems used in aircraft. It describes several types of air refrigeration systems:
1) Simple systems use compressed air cooled by a turbine-driven fan for ground cooling.
2) Bootstrap systems add a secondary compressor driven by the turbine to increase cooling capacity for high-speed aircraft.
3) Regenerative systems further cool air in a secondary heat exchanger using bled refrigerated air.
4) Reduced ambient systems use two turbines, one for cabin air and one for cooling air, driven by a single fan to cool air below ambient temperatures for supersonic aircraft.
Abrasive flow machining is a finishing process that uses a semi-solid abrasive putty to remove small amounts of material from workpieces. The putty is forced through or across the workpiece using hydraulic pressure to deburr, radius, polish and perform other surface finishing operations. It is well suited for finishing metals, ceramics and plastics in a uniform and economical manner, though it is not used for heavy material removal due to its low material removal rate. The process involves selecting abrasive media based on the material and desired finish, and using tooling and pressure to direct the flow of media through restrictions in the workpiece.
“Applications Of Powder Metallurgy In Reference with Cutting tools”Dushyant Kalchuri
Powder metallurgy is used for manufacturing products or articles from powdered metals by placing these powders in molds and are compacting the same using heavy compressive force. Typical examples of such article or products are grinding wheels, filament wire, magnets, welding rods, tungsten carbide cutting tools, self-lubricating bearings electrical contacts and turbines blades having high temperature strength. The manufacture of parts by powder metallurgy process involves the manufacture of powders, blending, compacting, profiteering, sintering and a number of secondary operations such as sizing, coining, machining, impregnation, infiltration, plating, and heat treatment.
Thermoforming is a process where a plastic sheet is heated and formed into a desired shape using pressure, vacuum, or mechanical methods. There are three main thermoforming methods: vacuum forming uses vacuum pressure to draw the heated sheet onto a mold; pressure forming uses compressed air to force the sheet onto the mold more quickly; and mechanical forming uses matching molds to shape the sheet without vacuum or pressure. Common materials thermoformed include plastics like ABS, polyethylene, and PVC. Applications include food packaging, automotive and aircraft parts.
In the Summer Air Conditioning system, the air is cooled, which is commonly joined by Dehumidification. In Summer, the outside condition is hot. Therefore, there will be a nonstop transfer of sensible heat as well as moisture from outside to the building. It is the sort of cooling, where the air is cooled and by and large dehumidified. The air provided to the adapted space is cooled and dehumidified. Sensible and latent heat loss from outside is an essential aspect of it.
Cryogenic insulations are needed to minimize heat transfer into storage tanks and transfer lines for cryogenic liquids. There are several types of insulation classified based on cost, weight, ease of application, and thermal conductivity. Expanded foams, gas-filled powders, and fiber materials provide insulation through a cellular or porous structure that reduces conduction and convection. Vacuum, evacuated, and opacified powder insulations further reduce conduction and radiation by removing gases. Multilayer insulation uses alternating conductive and non-conductive layers under vacuum to maximize reflection of radiation for optimal heat transfer prevention. The type used depends on the insulation needs and limitations of the specific cryogenic system.
The document describes the key components and operation of an ice plant, which uses ammonia as the primary refrigerant and a brine solution of ethylene glycol and water as the secondary refrigerant. The main components are the compressor, condenser, expansion valve, evaporator, ice cans, cooling tower, and pumps. The plant has three separate circuits - the refrigerant circuit with ammonia, the cooling water circuit, and the brine solution circuit which transfers heat from the water to produce ice using the ammonia refrigerant in a closed loop system.
The document discusses the history and principles of vapor absorption refrigeration systems. Some key points:
- Vapor absorption was first discovered in 1824 by Michael Faraday and the first machine was built in 1860. It uses a refrigerant (ammonia) that is absorbed into a solvent (water) for compression.
- Unlike vapor compression, it uses heat rather than mechanical energy to change the refrigerant's state. This allows it to be powered by waste heat or solar energy.
- The first domestic refrigerator using this technology was invented in 1925 and used ammonia, hydrogen, and water in a "three-fluid" system to eliminate the need for a pump.
The document provides an overview of additive manufacturing (AM) or 3D printing. It discusses the different families of AM, including powder bed fusion, material extrusion, binder jetting, vat photopolymerization, material jetting, direct energy deposition, and sheet lamination. It compares the various AM methods based on factors like deposition rate, feature resolution, part size limitations, and build speed. The document also outlines considerations for selecting suitable parts for AM and choosing the appropriate AM process based on the application.
A heat exchanger is a device that transfers heat between two or more fluids. There are several types of heat exchangers, including parallel-flow, counter-flow, cross-flow, double pipe, shell and tube, plate, and spiral. Heat exchangers are widely used in applications like heating, cooling, chemical processes, and power generation to efficiently exchange heat between fluids. Proper selection and maintenance of heat exchangers depends on factors such as temperature ranges, pressure, materials, fouling potential, and cleanability.
Unit 5 -RECENT TRENDS IN NON-TRADITIONAL MACHINING PROCESSESShanmathyAR2
Recent developments in non-traditional machining processes, their working principles, equipments,
effect of process parameters, applications, advantages and limitations. Comparison of non-traditional
machining processes.
Compressors complete description and a well arranged slides for the topic. That's too the point and relevant slide share you are looking for! Hope you will find it easy to understand
Thank you!
The document summarizes a student mini project on developing a thermoelectric air conditioning system. The system uses a thermoelectric Peltier module based on the Peltier effect to provide cooling without moving parts. It consists of a 12V Peltier device sandwiched between two heat sinks to dissipate heat, powered by a 12V battery. Fans are used to aid heat transfer. The document discusses thermoelectric principles, components used including specifications, assembly, advantages and limitations. The system was able to lower temperature by 2.11°C with a coefficient of performance of 0.8064 for cooling.
This document provides an overview of additive manufacturing (AM), also known as 3D printing. It defines AM as a process of joining materials layer by layer to make objects from 3D model data, as opposed to subtractive manufacturing methods. The document discusses different AM technologies including liquid-based, solid-based, powder bed fusion, and binder jetting. It also covers applications of AM in the medical and automotive industries, benefits of AM including design freedom and reduced material waste, and limitations such as part size restrictions.
The actual vapor compression cycle differs from the theoretical cycle in several ways that cause losses. In the actual cycle, the refrigerant leaves the evaporator as superheated vapor, compression is neither isentropic nor polytropic, and the refrigerant enters the expansion valve in a subcooled liquid state. Pressure drops also occur in the evaporator and condenser. Deviations from the theoretical cycle increase the required compressor work and can decrease the coefficient of performance. Changes in suction and discharge pressures also affect the refrigerating capacity and cost.
This document provides information on refrigerants including their definition, history, classification, properties, and environmental impact. It discusses early natural refrigerants and the development of artificial refrigerants over time. Refrigerants are classified based on their working principle and chemical properties. Key criteria for refrigerant selection include thermodynamic properties, environmental and safety factors, and cost. Common synthetic refrigerants discussed are CFCs, HCFCs, HFCs, hydrocarbons, and inorganic refrigerants like ammonia and carbon dioxide.
This document provides an introduction to non-conventional machining processes. It discusses how these processes use indirect energy like sparks, lasers, heat, or chemicals rather than direct contact between a tool and workpiece. Some key non-conventional machining processes described include electrical discharge machining, wire EDM, laser beam machining, electron beam machining, water jet machining, abrasive jet machining, ultrasonic machining, electrochemical machining, and electrochemical grinding. Advantages of these processes include high accuracy, less wear, longer tool life, and reduced environmental hazards compared to conventional machining.
The document discusses various methods of case hardening steel, which involves hardening only the surface layer while leaving the inner core relatively soft. The key methods covered are carburizing (including pack, liquid, and gas carburizing), cyaniding, nitriding, carbonitriding, induction hardening, flame hardening, and vacuum/plasma carburizing. The Jominy end quench test is described as a method to measure the hardenability or hardening depth of steels.
The document discusses refrigeration systems used in aircraft. It describes several types of air refrigeration systems:
1) Simple systems use compressed air cooled by a turbine-driven fan for ground cooling.
2) Bootstrap systems add a secondary compressor driven by the turbine to increase cooling capacity for high-speed aircraft.
3) Regenerative systems further cool air in a secondary heat exchanger using bled refrigerated air.
4) Reduced ambient systems use two turbines, one for cabin air and one for cooling air, driven by a single fan to cool air below ambient temperatures for supersonic aircraft.
Abrasive flow machining is a finishing process that uses a semi-solid abrasive putty to remove small amounts of material from workpieces. The putty is forced through or across the workpiece using hydraulic pressure to deburr, radius, polish and perform other surface finishing operations. It is well suited for finishing metals, ceramics and plastics in a uniform and economical manner, though it is not used for heavy material removal due to its low material removal rate. The process involves selecting abrasive media based on the material and desired finish, and using tooling and pressure to direct the flow of media through restrictions in the workpiece.
“Applications Of Powder Metallurgy In Reference with Cutting tools”Dushyant Kalchuri
Powder metallurgy is used for manufacturing products or articles from powdered metals by placing these powders in molds and are compacting the same using heavy compressive force. Typical examples of such article or products are grinding wheels, filament wire, magnets, welding rods, tungsten carbide cutting tools, self-lubricating bearings electrical contacts and turbines blades having high temperature strength. The manufacture of parts by powder metallurgy process involves the manufacture of powders, blending, compacting, profiteering, sintering and a number of secondary operations such as sizing, coining, machining, impregnation, infiltration, plating, and heat treatment.
Thermoforming is a process where a plastic sheet is heated and formed into a desired shape using pressure, vacuum, or mechanical methods. There are three main thermoforming methods: vacuum forming uses vacuum pressure to draw the heated sheet onto a mold; pressure forming uses compressed air to force the sheet onto the mold more quickly; and mechanical forming uses matching molds to shape the sheet without vacuum or pressure. Common materials thermoformed include plastics like ABS, polyethylene, and PVC. Applications include food packaging, automotive and aircraft parts.
In the Summer Air Conditioning system, the air is cooled, which is commonly joined by Dehumidification. In Summer, the outside condition is hot. Therefore, there will be a nonstop transfer of sensible heat as well as moisture from outside to the building. It is the sort of cooling, where the air is cooled and by and large dehumidified. The air provided to the adapted space is cooled and dehumidified. Sensible and latent heat loss from outside is an essential aspect of it.
Cryogenic insulations are needed to minimize heat transfer into storage tanks and transfer lines for cryogenic liquids. There are several types of insulation classified based on cost, weight, ease of application, and thermal conductivity. Expanded foams, gas-filled powders, and fiber materials provide insulation through a cellular or porous structure that reduces conduction and convection. Vacuum, evacuated, and opacified powder insulations further reduce conduction and radiation by removing gases. Multilayer insulation uses alternating conductive and non-conductive layers under vacuum to maximize reflection of radiation for optimal heat transfer prevention. The type used depends on the insulation needs and limitations of the specific cryogenic system.
The document describes the key components and operation of an ice plant, which uses ammonia as the primary refrigerant and a brine solution of ethylene glycol and water as the secondary refrigerant. The main components are the compressor, condenser, expansion valve, evaporator, ice cans, cooling tower, and pumps. The plant has three separate circuits - the refrigerant circuit with ammonia, the cooling water circuit, and the brine solution circuit which transfers heat from the water to produce ice using the ammonia refrigerant in a closed loop system.
The document discusses the history and principles of vapor absorption refrigeration systems. Some key points:
- Vapor absorption was first discovered in 1824 by Michael Faraday and the first machine was built in 1860. It uses a refrigerant (ammonia) that is absorbed into a solvent (water) for compression.
- Unlike vapor compression, it uses heat rather than mechanical energy to change the refrigerant's state. This allows it to be powered by waste heat or solar energy.
- The first domestic refrigerator using this technology was invented in 1925 and used ammonia, hydrogen, and water in a "three-fluid" system to eliminate the need for a pump.
The document provides an overview of additive manufacturing (AM) or 3D printing. It discusses the different families of AM, including powder bed fusion, material extrusion, binder jetting, vat photopolymerization, material jetting, direct energy deposition, and sheet lamination. It compares the various AM methods based on factors like deposition rate, feature resolution, part size limitations, and build speed. The document also outlines considerations for selecting suitable parts for AM and choosing the appropriate AM process based on the application.
A heat exchanger is a device that transfers heat between two or more fluids. There are several types of heat exchangers, including parallel-flow, counter-flow, cross-flow, double pipe, shell and tube, plate, and spiral. Heat exchangers are widely used in applications like heating, cooling, chemical processes, and power generation to efficiently exchange heat between fluids. Proper selection and maintenance of heat exchangers depends on factors such as temperature ranges, pressure, materials, fouling potential, and cleanability.
Unit 5 -RECENT TRENDS IN NON-TRADITIONAL MACHINING PROCESSESShanmathyAR2
Recent developments in non-traditional machining processes, their working principles, equipments,
effect of process parameters, applications, advantages and limitations. Comparison of non-traditional
machining processes.
Compressors complete description and a well arranged slides for the topic. That's too the point and relevant slide share you are looking for! Hope you will find it easy to understand
Thank you!
The document summarizes a student mini project on developing a thermoelectric air conditioning system. The system uses a thermoelectric Peltier module based on the Peltier effect to provide cooling without moving parts. It consists of a 12V Peltier device sandwiched between two heat sinks to dissipate heat, powered by a 12V battery. Fans are used to aid heat transfer. The document discusses thermoelectric principles, components used including specifications, assembly, advantages and limitations. The system was able to lower temperature by 2.11°C with a coefficient of performance of 0.8064 for cooling.
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.
Review on Design and Theoretical Model of Thermoelectricijsrd.com
This paper presents the theoretical development of the equations that allow to evaluate the performance of an air conditioning system based on the thermoelectric effect. The cooling system is based on a phenomena discovered by Jean Charles Athanase Peltier, in 1834. According to this when electricity runs through a junction between two semiconductors with different properties, heat is dissipated or absorbed. Thus, thermoelectric modules are made by semiconductors materials sealed between two plates through which a continuous current flows and keeps one plate hot and the other cold. The most important parameters to evaluate the performance of the device thermoelectric refrigeration are the coefficient of performance, the heat pumping rate and the maximum temperature difference between the hot side and the cold side of the thermoelectric module.
The document discusses heat pipes, including their types, working, components, and experimental setup used. It describes how heat pipes use evaporation and condensation to transfer heat from one location to another with low heat loss. The experiments tested a copper heat pipe with different working fluids and fill ratios. Results showed the heat pipe performed best with 100% fill ratio, demonstrating minimum temperature difference between the evaporator and condenser sections.
This document describes experiments conducted to determine the thermal conductivity of various materials and liquids. In experiment 1A, a guarded hot plate apparatus is used to measure the thermal conductivity of an insulating material sample. Experiment 1B involves determining the thermal conductivity of insulating powder packed between two copper spheres. Experiment 1C measures the thermal conductivity of a liquid using a guarded hot plate assembly to ensure one-dimensional heat conduction. Experiment 1D demonstrates a heat pipe and compares its temperature response over time to copper pipes, showing the heat pipe's nearly isothermal temperature distribution.
The techniques in which some physical parameters of the systems are determined and /or recorded as a function of temperature.
DSC is a thermal technique in which differences in heat flow into a substance and a reference are measured as a function of sample temperature while the two are subjected to a controlled temperature program.
Direct energy conversion involves transforming one form of energy directly into another without intermediate steps. This summary will discuss three methods of direct energy conversion:
1) Thermoelectric generators directly convert heat into electricity through the Seebeck effect using semiconductors. They have no moving parts and can operate with a simple design of p-type and n-type materials.
2) Fuel cells also directly produce electricity from chemical reactions without combustion, like the Grove fuel cell developed in 1839.
3) Thermoelectric photovoltaic cells directly convert sunlight into electricity through the photovoltaic effect in semiconductor junctions.
Heat transfer laboratory HEAT EXCHANGERSoday hatem
1. The document discusses heat exchangers and describes an experiment using a shell and tube heat exchanger. The objectives are to evaluate heat transfer coefficients, LMTD, heat transfer, and heat loss. Water is used as the hot and cold fluids flowing in counter-current configuration.
2. Key aspects covered include types of heat exchangers, theory behind heat transfer calculations, experimental procedures, results which did not match theory due to bubbles, and conclusions that objectives were still met despite non-ideal results.
3. The shell and tube heat exchanger uses water, with hot water inside tubes and cold water in the shell space. Heat is transferred between the streams in counter-current flow. Calculations
Evaluation of Convective Heat Transfer Coefficient of Air Flowing Through an ...Bishal Bhandari
The document evaluates the convective heat transfer coefficient of air flowing through an inclined circular duct. It describes an experimental setup used to study the effect of inclination angle and air velocity on the convective heat transfer coefficient. Tests were conducted by forcing air through a copper duct at various angles (0°, 30°, 60°, 90°, 120°, 150°) and velocities while keeping heat input constant. Temperature readings were used to calculate parameters like Reynolds number, Nusselt number, and the convective heat transfer coefficient. Results showed that the heat transfer coefficient peaks at a 90° inclination for an air velocity of 12 m/s, and is lowest at a 30° inclination for a velocity of 8.38 m/s
Performance Evaluation of Thermoelectric Materials: A Case Study of Orthorhom...inventionjournals
Designers often face the predicament of non-standardized and poor performing materials for thermoelectric module manufacturing. Other than analytical means, the only method to evaluate the performance of thermoelectric materials would be through experimental means. This work studies the experimental approach employed in performance investigation of thermoelectric materials using Orthorhombic SnSe crystals as a case study. The result obtained reveals the high thermoelectric conversion efficiency of orthorhombic crystals, and that they can operate as both low and high temperature thermoelectric material.
Thermoacoustic refrigeration uses sound waves to provide cooling without ozone-depleting refrigerants or moving parts. It was invented in 1992 by Steven Garrett and the first device, called the Space Thermoacoustic Refrigerator, was flown on the Space Shuttle Discovery. The main components are a driver to produce sound waves, a resonator containing a stack of plates through which the sound waves travel, transferring heat. As the waves compress and expand the gas, a temperature difference is created across the stack without vibration. Advantages include reliability, environmental friendliness, and low cost, though efficiency remains lower than conventional refrigerators.
Experimental and Analytical Performance of Gas Gap Cryogenic Thermal Switch ...ijsrd.com
This document discusses the experimental and analytical performance of a gas gap cryogenic thermal switch using nitrogen gas. The key points are:
1) A gas gap cryogenic thermal switch was fabricated and tested using liquid nitrogen storage. Thermal characteristics in the ON and OFF states were obtained by varying the heat load and measuring the temperature difference.
2) Thermal conductance increased with increasing heat load for both the ON and OFF states. Higher conductance and a smaller temperature difference indicated the ON state, while lower conductance and a larger temperature difference indicated the OFF state.
3) The experimental results matched well with theoretical calculations of thermal conductance, validating the analytical model. It was concluded that gas properties and gap geometry
Liquid Nitrogen Cooling in an Electronic Equipment under low pressureUsamaArifKhanNiazi
The document discusses spray cooling using liquid nitrogen (LN2) to cool electronic equipment under low pressure. It describes two theories that explain the spray cooling mechanism: thin film evaporation and convection, and secondary nucleation. Challenges at low pressure include LN2 flash evaporation. The study models heat and mass transfer between LN2 droplets and surroundings to determine temperature and pressure changes over time. Results show droplet lifetime is affected more by temperature than pressure. Continuous and intermittent LN2 spraying can control temperature by adjusting LN2 mass flow rates and switching spray nozzle frequencies.
1) The document discusses heat transfer analysis methods to optimize the water cooling scheme for combustion devices used in torpedo propulsion systems.
2) It describes the components of the combustion chamber including the inner and outer walls that form the coolant passageway. Heat transfer is highest in the nozzle throat region.
3) Methods for calculating heat transfer rates, temperatures, velocities and other parameters on both the gas and coolant sides are presented using equations from heat transfer theory. The analysis can be used to optimize the cooling system design.
Heat Transfer Analysis to Optimize The Water Cooling Scheme For Combustion De...IJERA Editor
Thermal Propulsion system is one kind of propulsion system which is used to drive torpedo. The present study focuses mainly on design of combustion device known to be thrust chamber or thrust cylinder. The chamber and nozzle wall and the injector face plate must be made of metals selected for high strength at elevated temperature coupled with good thermal conductivity, resistance to high temperature oxidation. chemical inertness on the coolant on the coolant side, and suitability for the fabrication method to be employed. In the case of certain monopropellants, the metal must not catalyze the decomposition. Although aluminum and copper alloys have been used successfully for combustion chambers and nozzles, stainless steels and carbon steels are in widest use today.A cooling jacket permits the circulation of a coolant, which, in the case of flight engines is usually one of the propellants. Water is the only coolant recommended. The cooling jacket consists of an inner and outer wall. The combustion chamber forms the inner wall and another concentric but larger cylinder provides the outer wall. The space between the walls serves as the coolant passage. The nozzle throat region usually has the highest heat transfer intensity and is, therefore, the most difficult to cool.
Thermodynamics describes systems and their ability to transfer and transform energy. A closed system does not allow mass transfer across its boundary, while an open system does. The zeroth law establishes thermal equilibrium, while the first law concerns energy conservation. The second law establishes that entropy always increases and heat naturally transfers from hot to cold bodies. Heat engines like steam power plants operate between a heat source and sink in a cycle to convert some heat into work, with efficiency limited by exhausting waste heat. The Carnot cycle achieves the highest possible efficiency between two temperatures. Real cycles like Rankine approximate Carnot but have additional practical considerations.
Heat exchangers transfer heat between two or more fluids that are at different temperatures. They work by bringing the fluids into thermal contact through a conducting surface while preventing mixing. There are several types of heat exchangers classified by their heat exchange process, fluid flow direction, mechanical design, and physical state. A common type is the shell and tube heat exchanger, which consists of a shell with a bundle of tubes inside. One fluid flows through the tubes while another flows over the tubes to transfer heat between the fluids. Double pipe heat exchangers are a simpler design with one pipe inside a larger pipe, allowing fluids to flow within and between the pipes.
This document discusses several methods for cooling power electronics including liquid cooling, air cooling, microchannel cooling, heat pipes, and jet impingement cooling. It also discusses using carbon nanotubes (CNTs) to improve polymer composites for applications in power electronics cooling. Microchannel cooling can provide high heat transfer coefficients but also high pressure drops. Heat pipes use phase change to passively circulate fluid for cooling. Jet impingement can provide high heat transfer but erosion may occur at high velocities. CNTs have excellent thermal and mechanical properties but achieving good dispersion in polymers is challenging.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Comparative analysis between traditional aquaponics and reconstructed aquapon...bijceesjournal
The aquaponic system of planting is a method that does not require soil usage. It is a method that only needs water, fish, lava rocks (a substitute for soil), and plants. Aquaponic systems are sustainable and environmentally friendly. Its use not only helps to plant in small spaces but also helps reduce artificial chemical use and minimizes excess water use, as aquaponics consumes 90% less water than soil-based gardening. The study applied a descriptive and experimental design to assess and compare conventional and reconstructed aquaponic methods for reproducing tomatoes. The researchers created an observation checklist to determine the significant factors of the study. The study aims to determine the significant difference between traditional aquaponics and reconstructed aquaponics systems propagating tomatoes in terms of height, weight, girth, and number of fruits. The reconstructed aquaponics system’s higher growth yield results in a much more nourished crop than the traditional aquaponics system. It is superior in its number of fruits, height, weight, and girth measurement. Moreover, the reconstructed aquaponics system is proven to eliminate all the hindrances present in the traditional aquaponics system, which are overcrowding of fish, algae growth, pest problems, contaminated water, and dead fish.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
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
2. WHAT IS CRYOGENICS
▪ Cryogenics is the production and behaviour of
materials at very low temperatures.
▪ Cryogenic processes involve temperatures
below -180 Celsius (123 k)
▪ The extremely low temperatures are produced
using substances called cryogens.
▪ Liquid Nitrogen is the most commonly used
cryogen (LN2).
2
3. 3
Liquid Nitrogen (LN2), a colourless, low
viscosity liquid that is widely used as a
cryogen.
A cryogenic rocket engine that uses a
cryogenic fuel.
4. ▪ The word cryogenics originates from the Greek
words ‘Cryo’ which means cold and ‘genics’
which means to produce.
▪ The cryogenic processes also have a unique
ability to recycle difficult to separate composite
materials.
▪ Cryogens are stored in vessels called as
Dewar flasks which provide good insulation.
Liquid helium (LH2) is another commonly used
cryogen.
4
6. A Compact thermal heat
switch for cryogenic space
applications operating near
100 k
AUTHORS- M. Dietrich, A. Euler, G. Thummes
PUBLICATION-Cryogenics, Volume 59, January-February 2018
7. THERMAL HEAT SWITCH
▪ A thermal switch is an electrical safety device
that interrupts electric current when heated to a
specific temperature.
▪ It is a device which opens at a high temperature
and re closes when the temperature drops.
▪ Thermal switches are used in power supplies in
case of overload, and also as thermostats in
some heating and cooling systems.
7
9. CRYOCOOLERS
A refrigerator designed to reach cryogenic temperatures is
often called a Cryocooler.
The term is most often used for smaller systems, typically
table-top size, with input powers less than about 20 kW.
In most cases cryocoolers use a cryogenic fluid as the working
substance and employ moving parts to cycle the fluid around a
thermodynamic cycle.
The fluid is typically compressed at room temperature,
precooled in a heat exchanger, then expanded at some low
temperature
9
10. ▪ The returning low-pressure fluid passes through the heat
exchanger to precool the high-pressure fluid before
entering the compressor intake.
10
11. HIGHLIGHTS
▪ A thermal heat switch has been developed intended for
cryogenic space applications operating around 100 K.
▪ The switch was designed to separate two pulse tube cold
heads that cool a common focal plane array.
▪ A construction based on the difference in the linear
thermal expansion coefficients (CTE) of different
materials was chosen.
▪ A simple design is proposed based on thermoplastics
which have one of the highest CTE known permitting a
relative large gap width in the open state
11
12. ▪ After a single switch was successfully built, a second double-
switch configuration was designed and tested.
▪ The long term performance of the chosen thermoplastic (ultra-
high molecular weight polyethylene) under cryogenic load is also
analyzed.
▪ The heat switch is a proof of concept for a redundant cryocooler
application.
▪ The creep of the used CTE material at cryogenics temperatures
was analyzed.
12
13. INTRODUCTION
• Cryocoolers for space applications in the 77 K range are of
the pulse-tube type combined with a flexure bearing
compressor.
• As part of a research project studying various redundancy
concepts for satellite operations, a heat switch was
developed including two cold heads (CH1 and CH2) mounted
on a single focal plane array detector.
• The heat switch thermally connects an active cold head to
the FPA while increasing the thermal contact resistance to a
second cold head in stand-by mode, thus reducing the heat
load of the stand-by system to the active cold head.
13
15. WHY A CTE IS USED INSTEAD OF OTHER HEAT SWITCHES?
▪ There exist various kinds of heat switches for space
applications, each having their own advantages and
disadvantages.
▪ Most common are heat switches of the Gas-Gap and
CTE-based (CTE: linear thermal coefficient of expansion)
▪ In Gas-Gap switches the pressure of a gas in a small gap
is controlled. This can be done e.g. by use of absorbers or
valves connected to gas reservoirs. The
presence/absence of the gas in the small gap (typically
100 lm) enables/disables a thermal contact.
15
16. ▪ The CTE-based switches rely on the thermal expansion of
one or more components.
▪ When the temperature decreases the high CTE material
‘‘shrinks’’ and closes the gap between the two solids.
▪ Below a certain ‘‘switching temperature’’, the gap is fully
closed, thus providing a heat conduction path.
▪ By using thermoplastics with a high CTE, such as ultra-high
molecular weight polyethylene (UHMW-PE), in order to
circumvent the requirement of tiny gaps, the CTE-based
switch becomes superior compared to other designs with
respect to the required temperature range and standards
for space applications.
16
17. THERMAL HEAT SWITCH CONCEPT
▪ The switch needs to serve as a support for the FPA, the contact
areas that are connected to the cold head and FPA must not
move upon switching.
▪ The switch should exhibit an on-state thermal conductivity of
more than 1 W/K at an operating temperature between 80 and
100 K and an off-state conductivity of less than 1 mW/K.
▪ Unfortunately, high thermal conductivity materials, such as
metals, exhibit a rather small CTE leading to a small gap sizes
which require careful manufacturing and increase the risk of
failure.
▪ This leads to a design where a thermoplastic is used as the
switching element only, bringing two metals with high thermal
conductivity into contact.
17
18. ▪ The graph below shows the CTE between 80 K and 300 K of
some metals and thermoplastics.
18
19. ▪ While most metals exhibit a CTE of 10–20 10^6 /K,
polytetrafluoroethylene (PTFE) for example has an order of
magnitude higher CTE compared to copper at room temperature.
▪ PTFE shows two solid–solid phase transitions near room
temperature with a maximum CTE of more than 500*10^-6/K.
▪ Measurements using liquid nitrogen revealed that ultra-high-
molecular-weight polyethylene (UHMWPE) has an even higher
thermal contraction than PTFE between room temperature and
77 K.
▪ When designing a CTE-based switch, one important parameter
is the gap width, which depends on the CTE material and the
desired switching temperature.
19
20. ▪ Two switches were built: a single switch connected to a single
cold head and heat load, which was used for initial testing.
▪ Later on, a second switch was built which has a T-form to
connect two cold heads to a single load located in the middle of
the switch.
▪ The part connected to the heat load (detector side) consists of
an inner shaft made of a solid copper cylinder (10 mm diameter)
with a flange on one end.
▪ The part connected to the cold head (PE-side) consists of a
copper flange with four integrated copper jaws that are
separated from the inner cylinder by the gap.
▪ The distribution of stress inside the switch components was
calculated using Hooke’s law.
20
22. ▪ The contact pressure of the jaws to the shaft at 100 K was estimated to be
1.4 MPa, while the maximum tensile stress in the UHMWPE was estimated to
be 5 MPa.
22
shows the compressive and tensile stresses in radial and tangential (= circumferential)
directions inside the switch components, calculated at an operating temperature of 100 K
24. ▪ The test apparatus consists of a coaxial pulse tube cold head driven by
an AIM SL400 linear compressor to which the single switch is attached.
▪ During the measurement a constant heat load of 500 mW is being
applied to the detector side of the switch.
▪ The detector side of the switch maintains a constant temperature until
the switch closes at a temperature of about 220 K.
▪ After that, the detector side cools down quickly until it reaches the cold
head temperature.
▪ From there on, both temperatures further decrease until the base
temperature of 57 K is reached.
▪ At 2.5 h the compressor is turned off. Both temperatures start to rise
until the switch opening temperature of about 250 K is reached.
▪ From there on, the cold head temperature rises slower than the sensor
temperature because of the low thermal coupling in the off-state.
24
25. ▪ After 6 h the heater is switched off and after around 6.5 h the cooler
and heater are started again and the next cycle begins.
▪ There exists a small hysteresis of about 25 K due to the lag of the
UHMW-PE temperature with respect to the cold head temperature.
25
26. Long term performance of UHMW-PE
▪ For long term satellite missions it is essential to know how the
materials used in the switch will degrade in their properties during
mission lifetime.
▪ It is known that thermoplastics tend to creep over time, which would
have a significant effect on the switch performance.
▪ Material pre-aging can significantly reduce long term creep, whereas
other methods like material-enforcement tend to reduce the CTE.
▪ Long term creep measurements for UHMW-PE have been studied for
room temperatures and above, mainly because of their application in
the medical sector
▪ A test apparatus was built for testing the creep of our UHMW-PE
samples at low temperatures using strain gauges (type Micro-
Measurements EK-13-250BF-10C/W)
26
28. ▪ The UHMW-PE samples were in form of a solid cube with an edge
length of 20 mm.
▪ The graph shows the compliance data under a compressive load of 1
MPa for several temperatures. Similar results are expected for tensile
stresses.
▪ After some initial relaxation processes on a time scale of less than
10,000 s, it appears that the material starts to creep linearly on a
logarithmic time scale.
▪ At least for the 100 K data this is in accordance with the research work
which used short term measurements near room temperature to
predict low temperature creep data for temperatures T < Tg , where
Tg = 130 K is the glass transition temperature of UHMW-PE.
▪ For a mission time of 10 years, a creep compliance of 0:2 GPa1 at 100
K can be roughly extrapolated
28
29. Conclusions
▪ Two variants have been studied: a single and a double heat switch
configuration.
▪ The single switch showed a state change around 220 K, and an
on/off-state conductivity of more than 1 W/K and an 3 mW/K
respectively.
▪ The double switch was successfully tested in a two cooler
configuration and showed reliable switching characteristics over
several cycles.
▪ UHMW-PE, which was used as the high CTE material, shows a rather
high creep rate under uniaxial pressure at room temperature.
29
30. ▪ To estimate the degeneration of the material during switch operation at
cryogenic temperatures, creep tests were performed and extrapolated
for long term prediction.
▪ At 100 K, the compliance is estimated to be 0:2 GPa1 in 10 years
resulting in a 12% drop in contact pressure during on-state.
▪ The CTE-based thermal switch presented in this paper is a promising
concept.
▪ Further development will focus on mechanical properties as stability and
weight.
30
31. OTHER APPLICATIONS OF CRYOGENICS
▪ Electric power transmission in big cities
▪ Frozen food
▪ Blood banking
▪ Infrared sensors
▪ Electronics
▪ Nuclear Magnetic Resonance
▪ Experimental research on certain physics phenomena.
31
36. References
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