# HVAC Course (What is Refrigeration?)
Refrigeration is achieved by removing heat at low temperature level and rejecting at a relatively high temperature level.
By the nature heat flows from high temperature to low temperature.
So, transfer heat form low to high temperature required external sources.
# HVAC Course (How Does a Refrigerator Works?)
In the refrigeration cycle, there are five basic components:
: fluid refrigerant;
: a compressor, which controls the flow of refrigerant;
: the condenser coils (on the outside of the fridge);
: the evaporator coils (on the inside of the fridge);
: and something called an expansion device.
Working Process of Domestic Refrigerator
1. The compressor constricts the refrigerant vapor, raising its pressure, and pushes it into the coils on the outside of the refrigerator.
2. When the hot gas in the coils meets the cooler air temperature of the kitchen, it becomes a liquid.
3. Now in liquid form at high pressure, the refrigerant cools down as it flows into the coils inside the freezer and the fridge.
4. The refrigerant absorbs the heat inside the fridge, cooling down the air.
5. Last, the refrigerant evaporates to a gas, then flows back to the compressor, where the cycle starts all over.