Refrigeration Cycle: Refrigeration Condensers

The first law of thermodynamics teaches us that heat can not be created or destroyed, but it can be moved. The refrigeration cycle leverages this law by “moving” heat from an area or object where it is unwanted to somewhere that it will “do no harm”. In a refrigeration cycle, the condenser is the heat exchanger responsible for “rejecting” the heat gained in the evaporator and compressor. Most often, the heat is expelled into the atmosphere, but other heat-receiving media can be employed as well. 

A refrigeration condenser receives high-pressure, superheated vapor from the compressor. As the refrigerant passes through the condenser, its temperature is lowered, and the vapor is cooled. Once the refrigerant becomes saturated, it continues to reject heat, but now in the “latent” form as the vapor transitions into a liquid at a constant temperature. High-pressure, saturated liquid exits the condenser and enters a high pressure receiver or is piped directly to an expansion device. 

There are three primary categories of refrigeration condensers:

1. Evaporative Condensers
2. Water-Cooled Condensers
3. Air-Cooled Condensers

Evaporative condensers use a combination of air and water to cool the refrigerant which results in lower condensing pressure and efficient operation. 

Water-cooled condensers utilize a heat exchanger with cooling water that is pumped from a remote cooling tower. The water absorbs heat from the refrigerant and is returned to the tower where the heat is rejected to the atmosphere. 

Air-cooled condensers are the simplest type of condenser and use fans to move air over the condenser coil surface. No water is employed in air-cooled condensers. This results in the highest condensing pressure of the three categories. Historically, air-cooled condensers have been limited to residential and commercial refrigeration systems, but are gaining popularity in low-charge ammonia systems because of their simplicity.