STEP 1: A refrigerant transports the heat
In the heat pump's closed circuit, a refrigerant takes over the task of transmitting and transporting the heat. The question is, where is the actual again in heat that is so typical for heat pumps? - The answer is quite simple: in the evaporator!
STEP 2: The refrigerant evaporates in the evaporator
Evaporators function is to bring the liquid refrigerant to a boil or to evaporate at very low temperatures and thereby storing the energy that is absorbed. The refrigerant is therefore no longer liquid but gaseous. The cycle is repeated...
STEP 3: The gas is heated under pressure
The refrigerant gas volume in the compressor is now reduced. Of course the pressure increases. And also the temperature of the refrigerant. The hot refrigerant now flows to the condenser. This is a heat exchanger in which the recovered environmental heat is transferred to the heating system.
STEP 4: Refrigerant cools and takes on heat again
Due to the cooling process the refrigerant returns to liquid form again; in this process it can absorb new heat from the environment after a pressure and temperature sink in the expansion valve. The cycle begins anew.