A heat pump is a device that transfers heat from a lower temperature medium to a higher temperature medium with the assistance of a power source. Basically, a heat pump operates in a similar manner as the air conditioner does, but in reverse
Heat pump thermal Cycle
A Heat pump comprises a refrigerant circuit, filled with a special fluid (refrigerant). Depending on the temperature and pressure operating conditions in which it is working, will be in either a gaseous or liquid state. The refrigerant circuit consists mainly:
The heat pump thermal cycle is best described through the flow of the refrigerant through the prescribed heat pump components. Starting at the discharge side of the compressor, the refrigerant is in a gaseous state, has been compressed and is therefore hot and at high pressure. It passes into the condenser (a brazed plate Heat exchanger) where it releases most of its heat. As it cools it changes state (condenses) to a liquid which is warm and at high pressure. This warm liquid refrigerant passes through a pressure reducing device (the expansion valve) as temperature and pressure are directly linked; pressure drop causes the sudden temperature of the refrigerant to plummet. In addition, some of the refrigerant evaporates and the result is a low temperature mix of liquid and gaseous refrigerant that is known as “Flash Gas”. This mixture then passes to another brazed plate heat exchanger, the evaporator, where the refrigerant, in this gaseous state, passes to the compressor where it is pressurized, heated and circulated back around the system.