File Name: refrigeration air conditioning and heat pumps .zip
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump , air conditioning and refrigeration systems. A heat pump is a mechanical system that allows for the transmission of heat from one location the "source" at a lower temperature to another location the "sink" or "heat sink" at a higher temperature. In either case, the operating principles are close. According to the second law of thermodynamics heat cannot spontaneously flow from a colder location to a hotter area; work is required to achieve this.
Similarly, a refrigerator moves heat from inside the cold icebox the heat source to the warmer room-temperature air of the kitchen the heat sink. The operating principle of ideal heat engine was described mathematically using Carnot cycle by Sadi Carnot in An ideal refrigeration or a heat pump system can be thought of as an ideal heat engine that is operating in a reverse Carnot cycle.
Heat pump and refrigeration cycles can be classified as vapor compression , vapor absorption , gas cycle , or Stirling cycle types. The vapor-compression cycle is used in most household refrigerators as well as in light commercial, commercial, and industrial refrigeration systems.
Figure 1 provides a schematic diagram of the components of a typical vapor-compression refrigeration system. The thermodynamics of the cycle can be analysed on a diagram   as shown in Figure 2. In this cycle, a circulating working fluid commonly called refrigerant such as Freon enters the compressor as a low pressure and low temperature vapor. The vapor is compressed at constant entropy and exits the compressor superheated.
The superheated vapor travels through the condenser which first cools and removes the superheat and then condenses the vapor into a liquid when releasing additional heat at constant pressure and temperature.
The liquid refrigerant goes through the expansion valve also called a throttle valve where its pressure abruptly decreases, causing flash evaporation and auto-refrigeration of, typically,a small portion of the liquid. That results in a mixture of liquid and vapor at a lower temperature and pressure. The cold liquid-vapor mixture then travels through the evaporator coil or tubes and is completely vaporized by cooling the warm air from the space being refrigerated being blown by a fan across the evaporator coil or tubes.
The resulting refrigerant vapor returns to the compressor inlet to complete the thermodynamic cycle. The above discussion is based on the ideal vapor-compression refrigeration cycle, and does not take into account real-world effects like frictional pressure drop in the system, slight thermodynamic irreversibility during the compression of the refrigerant vapor, or non-ideal gas behavior if any.
In the early years of the twentieth century, the vapor absorption cycle using water-ammonia systems was popular and widely used but, after the development of the vapor compression cycle, it lost much of its importance because of its low coefficient of performance about one fifth of that of the vapor compression cycle.
Nowadays, the vapor absorption cycle is used only where heat is more readily available than electricity, such as industrial waste heat , solar thermal energy by solar collectors , or off-the-grid refrigeration in recreational vehicles.
The absorption cycle is similar to the compression cycle, except for the method of raising the pressure of the refrigerant vapor. In the absorption system, the compressor is replaced by an absorber and a generator.
The absorber dissolves the refrigerant in a suitable liquid dilute solution and therefore the dilute solution becomes a strong solution. Then, a liquid pump would move the strong solution from the absorber to a generator where, on heat addition, the temperature and pressure increase. Then the refrigerant vapor is released from the strong solution, which turns into the dilute solution and is moved back to the absorber by the liquid pump.
Some work is required by the liquid pump but, for a given quantity of refrigerant, it is much smaller than needed by the compressor in the vapor compression cycle. However, the generator requires a heat source, which would consume heating energy unless waste heat is used.
In an absorption refrigerator, a suitable combination of refrigerant and absorbent is used. The most common combinations are ammonia refrigerant and water absorbent , and water refrigerant and lithium bromide absorbent.
Absorption refrigeration systems can be powered by fossil energies i. When the working fluid is a gas that is compressed and expanded but does not change phase, the refrigeration cycle is called a gas cycle. Air is most often this working fluid. As there is no condensation and evaporation intended in a gas cycle, components corresponding to the condenser and evaporator in a vapor compression cycle are the hot and cold gas-to-gas heat exchangers.
For given extreme temperatures, a gas cycle may be less efficient than a vapor compression cycle because the gas cycle works on the reverse Brayton cycle instead of the reverse Rankine cycle. As such, the working fluid never receives or rejects heat at constant temperature. In the gas cycle, the refrigeration effect is equal to the product of the specific heat of the gas and the rise in temperature of the gas in the low temperature side.
Therefore, for the same cooling load, gas refrigeration cycle machines require a larger mass flow rate, which in turn increases their size.
Because of their lower efficiency and larger bulk, air cycle coolers are not often applied in terrestrial refrigeration. The air cycle machine is very common, however, on gas turbine -powered jet airliners since compressed air is readily available from the engines' compressor sections.
These jet aircraft's cooling and ventilation units also serve the purpose of heating and pressurizing the aircraft cabin. The Stirling cycle heat engine can be driven in reverse, using a mechanical energy input to drive heat transfer in a reversed direction i.
There are several design configurations for such devices that can be built. Several such setups require rotary or sliding seals, which can introduce difficult tradeoffs between frictional losses and refrigerant leakage. The Carnot cycle is a reversible cycle so the four processes that comprise it, two isothermal and two isentropic, can also be reversed. When a Carnot cycle runs reversely, it is called a reversed Carnot cycle.
A refrigerator or heat pump that acts on the reversed Carnot cycle is called a Carnot refrigerator or Carnot heat pump respectively. In the first stage of this cycle, the refrigerant absorbs heat isothermally from a low-temperature source, T L , in the amount Q L. Next, the refrigerant is isentropically compressed and its temperature rises to that of the high-temperature source, T H.
Then at this high temperature, the refrigerant rejects heat isothermally in the amount Q H. Also during this stage, the refrigerant changes from a saturated vapor to a saturated liquid in the condenser. Lastly, the refrigerant expands isentropically until its temperature falls to that of the low-temperature source, T L. The efficiency of a refrigerator or heat pump is given by a parameter called the coefficient of performance COP. Both the COP of a refrigerator and a heat pump can be greater than one.
Combining these two equations results in:. In a worst-case scenario, the heat pump will supply as much energy as it consumes, making it act as a resistance heater. However, in reality, as in home heating, some of Q H is lost to the outside air through piping, insulation, etc. Therefore, the system used to heat houses uses fuel.
From Wikipedia, the free encyclopedia. For details of practical heat pumps, see Heat pump. Mathematical models of heat pumps and refrigeration. The classical Carnot heat engine. Classical Statistical Chemical Quantum thermodynamics.
Zeroth First Second Third. System properties. Note: Conjugate variables in italics. Work Heat. Material properties. Carnot's theorem Clausius theorem Fundamental relation Ideal gas law. Free energy Free entropy. History Culture. History General Entropy Gas laws.
Entropy and time Entropy and life Brownian ratchet Maxwell's demon Heat death paradox Loschmidt's paradox Synergetics. Caloric theory Theory of heat. Heat ". Thermodynamics Heat engines. Nucleation Self-assembly Self-organization Order and disorder. Main article: Vapor-compression refrigeration. Figure 1: Vapor-compression refrigeration.
Figure 2: Temperature—Entropy diagram of the vapor-compression cycle. Main article: Absorption refrigerator. This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. June Learn how and when to remove this template message. Main article: Stirling engine. Boles Retrieved Archived from the original on Modern Refrigeration and Air Conditioning.
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This Book provides an clear examples on each and every topics covered in the contents of the book to provide an every user those who are read to develop their knowledge. Refrigeration, Air Conditioning and Heat Pumps written to meet exhaustively the requirements of various syllabus in the subject of the courses in B.
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump , air conditioning and refrigeration systems. A heat pump is a mechanical system that allows for the transmission of heat from one location the "source" at a lower temperature to another location the "sink" or "heat sink" at a higher temperature. In either case, the operating principles are close. According to the second law of thermodynamics heat cannot spontaneously flow from a colder location to a hotter area; work is required to achieve this. Similarly, a refrigerator moves heat from inside the cold icebox the heat source to the warmer room-temperature air of the kitchen the heat sink.
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In , proceedings for this conference included papers from authors all over the world. For , we are soliciting papers on topics ranging from fundamental to applied, including heat transfer and fluid flow fundamentals, alternative refrigerants and working fluids, modeling of components and systems, heat exchanger enhancements and characterizations, controls, diagnostics, domestic, commercial and industrial refrigeration, heat pumps, transport refrigeration and air conditioning. Abdalla, Siddharth Pannir, and Elgenied Khalid. Bahman, Davide Ziviani, and Eckhard A. Hugenroth, and Eckhard A. Evaluation of binary and ternary refrigerant blends as replacements for Ra in an air-conditioning system , Ian Bell, Piotr Domanski, Greg Linteris, and M.
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In this study, an existing laboratory heat pump is converted to a refrigeration unit in order to evaluate efficiency, power consumption, pressure and temperature variations and optimal charge amount of the system in new mode using refrigerant RC. Refrigerant charge amount has a key role in the terms of performance, operating cost regarding to the charge reduction and energy consumption and environmental concerns in all heat pump and refrigeration systems, which work on the same principles. Heat pump charge amount is the subject of many research, but less studies have been done in the case of refrigerators and freezers where the system works in the transient condition, on the contrary to the heat pump units. Although this study has been devoted to a detailed attempt to examine the possibility of converting the heat pump into the refrigerator, energy aspects of the whole system and the compressor have been analyzed under different working conditions. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve. Int J Energy Res 28 9 —
Refrigeration, Air Conditioning and Heat Pumps, Fifth Edition, provides a comprehensive introduction to the principles and practice of refrigeration. Clear and comprehensive, it is suitable for both trainee and professional HVAC engineers, with a straightforward approach that also helps inexperienced readers gain a comprehensive introduction to the fundamentals of the technology. With its concise style and broad scope, the book covers most of the equipment and applications professionals will encounter. The simplicity of the descriptions helps users understand, specify, commission, use, and maintain these systems. It is a must-have text for anyone who needs thorough, foundational information on refrigeration and air conditioning, but without textbook pedagogy. It includes detailed technicalities or product-specific information. New material to this edition includes the latest developments in refrigerants and lubricants, together with updated information on compressors, heat exchangers, liquid chillers, electronic expansion valves, controls, and cold storage.
In , proceedings for this conference included papers from authors all over the world. For , we are soliciting papers on topics ranging from fundamental to applied, including heat transfer and fluid flow fundamentals, alternative refrigerants and working fluids, modeling of components and systems, heat exchanger enhancements and characterizations, controls, diagnostics, domestic, commercial and industrial refrigeration, heat pumps, transport refrigeration and air conditioning. Latini, P.
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