Cycles of the Fridge

Compressor

• When the thermostat in your fridge detects that the interior temperature is too high, the compressor engages and draws in the circulating refrigerant vapor. The compressor uses a motor-driven piston to compress the vapor and push it out of the exhaust valve into the next part of the cycle -- the condenser. After exiting the compressor, the refrigerant is still in vapor form, but under more pressure and hotter than when it entered.

Condenser

• When the hot, pressurized refrigerant enters the condenser, it is cooled with either air, driven by a fan, or water. The condenser itself is a long, thin tube covered with metal fins to increase the surface area available for effective cooling action. Because the refrigerant in the condenser is under pressure, removing heat causes much of it to condense into a liquid. The liquid moves from the condenser tube to the next part of the cycle, the expansion valve.

Expansion Valve

• The expansion valve is a gateway between an area of the refrigeration system that is under high pressure -- the condenser -- and an area of low pressure -- the evaporator. The valve is essentially a tiny hole that only allows a small amount of the liquid refrigerant through at a time. Without the expansion valve, the pressure in the condenser and the evaporator would equalize; with the valve, the compressor sucks vapor from the evaporator, keeping pressure low, and forces it into the condenser, where pressure is high.

Evaporator

• The evaporator is the final stage in the refrigeration cycle. When the liquid refrigerant is sucked from the condenser through the expansion valve and into this area of low pressure finned tubing, its temperature plummets lower than that of the air inside the fridge. A fan blows that warmer air across the evaporator tubing, cooling it. As the temperature of the refrigerant inside rises, it vaporizes and is sucked into the compressor once more, completing the cycle.