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HEAT PUMP SYSTEM AND ITS WORKING PRINCIPLE

 The heat pump is a cyclic device which is able to extract energy at a low  temperature heat source and upgrade it to a high temperature heat source, enabling it to be used more effectively. Low grade reject heat available at low temperature may be upgraded  to high temperature heat source by a heat pump. While refrigerator is meant for the removal of heat and to achieve cooling, a heat pump is used to supply   heat at a high temperature.



 Heat pump systems may have many features in common with the refrigeration systems and may be of   the vapor compression or the absorption type. A typical vapor compression heat pump for space heating   has the same  basic components as the vapor - compression refrigeration system : compressor,   condenser, expansion valve  and evaporator. The heat Qin comes from the surroundings (cold air) , and Qout is directed to the dwelling as the desired effect, with the COP given by, 

COP = Qout /  Wc  = (h2-h3) / ( h2-h1)

many possible sources are available for heat transfer Qin to the refrigerant passing through the evaporator. These include the outside air, the ground, and water from lakes, rivers, or wells. Liquid circulated through a solar collector and stored in an insulated tank also can be used as a source for a heat pump. Industrial heat pumps employ waste heat or warm liquid or gas streams as the low temperature heat source and upgrade it. 

An air-air heat pump can be used for year- around air conditioning, to achieve heating during winter and cooling during summer, by using a reversing valve with the evaporator and condenser executing opposite duties. A heat pump in industry will be very effective if both condenser and condenser are utilized for heating and cooling respectively 

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