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A heat pump is a device that uses work to transfer heat from a cool space to a warm space by transferring thermal energy using a refrigeration cycle, cooling the cool space and warming the warm space. In cold weather a heat pump can move heat from the cool outdoors to warm a house; the pump may also be designed to move heat from the house to the warmer outdoors in warm weather. As they transfer heat rather than generating heat, they are more energy-efficient than other ways of heating a home.
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.
Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services.
Replacing conventional boilers by air to water heat pumps represents a major market opportunity and a contribution to more sustainable heating approaches. However, such retrofit situation impose tough technical requirements which must be met in order to de ...
1997
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Intube flow boiling experiments for refrigerant R-134a mixed with a lubricating oil are reported. The tests were run at a nominal inlet pressure of 3.4 bar over a wide range of vapor qualities at mass velocities of 100, 200 and 300 kg/m2s (73500, 147000 an ...
The objectives of the present work is to theoretically and experimentally demonstrate the advantages of a two-stage cycle equipped with an economizer and single variable speed compressor for heat pumps using air as cold source. Furthermore, an efficient de ...