We know that the air-conditioning system is used for cooling the room in summers when atmospheric temperatures are very high, but do you know that the air-conditioner can also be used to heat the room during winter conditions? Actually the air-conditioner which is used for heating the room is called as heat pump. The components of the heat pump are exactly same as the air conditioner; the only difference is that the heat pump works in direction opposite to that of the air conditioners. The heat pump is reverse air conditioner or refrigerator.
Heat pump is the devise which is used to carry the heat from atmosphere which is at low temperature to the room which is at high temperature. Thus heat pump is the devise in which heat is carried from low temperature reservoir to the high temperature reservoir. The second definition of the heat pump is exactly same as the air conditioner or the refrigerator or even the freezer.
As per the second law of thermodynamics, the natural tendency of the heat is to flow from the high temperature reservoir to the low temperature reservoir, but in the heat pump the heat travels from low temperature reservoir to the high temperature reservoir. Since this is against the natural flow of heat, some external work has to be supplied to the heat pump in order to enable the transfer of heat from low temperature to the high temperature reservoir.
