Moving Refrigerant from the Evaporator to the Condenser
Two components set up the pressure differentials needed to make the refrigerant travel from the evaporator (where heat is absorbed) and into the condenser (where the heat is released). These are the compressor and the capillary tube.
The compressor is a motor driven pump that pulls refrigerant vapor out of the evaporator and pushes it into the condenser. A cam drives a piston backwards and forward in a cylinder .. At the opposite end of the cylinder, two valves open and close to allow refrigerant to be pulled into and expelled from the cylinder.
There are a few types of compressors that are used in appliances. Refrigerators use standard reciprocating compressors, their differences is how the electric motor inside rotates the piston to create compression on the refrigerant within the system.
Then there are linear compressors. Linear compressors use a piston as well and these are mainly used by LG and for a short time they were used on some Whirlpool model refrigerators.
On the intake stroke, the movement of the piston closes the exhaust valve and opens the suction valve. This allows refrigerant vapor to be pulled into the chamber. On the exhaust stroke, the piston forces the suction valve closed and pushes the exhaust valve open to allow the refrigerant vapor to be pushed into the condensing coil.