Refrigeration Cycle

What Is the Refrigeration Cycle?

The refrigeration vapor compression cycle is the path that refrigerant takes through your commercial HVAC system’s components to facilitate heat transfer and cooling. A refrigeration cycle at a minimum consists of a compressor, condenser, expansion device and evaporator components. Successful completion of the refrigeration cycle is essential for maintaining comfort in commercial spaces during warmer months. The cycle works by removing heat from the interior of the building, effectively cooling it down.

Components of the HVAC Refrigeration Cycle

The refrigerant cycle as stated above has four fundamental components: the compressor, the condenser, the expansion device, and the evaporator. Let's examine each one:

1. Compressor: The compressor is the powerhouse of the cooling system, typically located in the outdoor unit . It pressurizes and circulates the refrigerant throughout the HVAC system. The refrigerant enters the compressor as a low-pressure gas, and the compressor transforms it into a high-pressure, high-temperature gas, which is then moved through the discharge line to the condenser.
2. Condenser (Condenser Coil): Situated in the outdoor unit, the condenser receives high-pressure gas from the compressor. As the refrigerant passes through the condenser coil, it releases heat to the outside air and condenses into a liquid form.
   
3. Expansion Device: The high-pressure liquid refrigerant then moves to the expansion device, which reduces its pressure before it enters the evaporator. This rapid depressurization cools the refrigerant, like how releasing air from a can of compressed air causes cooling.
   
4. Evaporator: Next, the chilled liquid refrigerant flows into the evaporator coil, which consists of finned tubes. In split systems, the evaporator is installed inside your commercial space, where it absorbs heat from the warm indoor air, changing the refrigerant from liquid to gas. In packaged units, the evaporator coil is contained within the unit, and the refrigerant undergoes the same liquid-to-gas transformation as it absorbs heat from a mixture of outdoor air and recirculated air from the space. The heated gas then moves to the compressor, and the refrigerant cycle starts again.

The individual components are connected by refrigerant piping in a closed system. The suction line connects the evaporator to the compressor, the discharge line connects the compressor to the condenser, and the liquid line connects the condenser to the evaporator. The expansion device is located in the liquid line.

Basic Refrigeration System

A vapor compression refrigeration system can reject heat in either direction depending on how it is applied for the application. In the summer, heat is removed from the space to provide comfort, and this heat is rejected to the outside. In the wintertime, the refrigeration cycle can be reversed or designed as a heat pump, which then moves heat from cooler outdoor temperature and provides heating comfort to the occupied space. A heat pump runs in reverse from an air conditioner where the coil inside your building becomes the hot coil (the condenser), so that as the air in your facility blows across the coil, it is heated up, keeping your building warm.

Issues That Can Disrupt the Refrigeration Cycle

Common problems in the commercial HVAC refrigeration cycle can cause your air conditioning system or heat pump to struggle or even fail to cool or heat your building adequately. Some issues include

• Low refrigerant
• Refrigerant leaks
• System blowing warm air
• Dirty coils
• Frozen evaporator coil
• Short cycling (system turning on and off frequently)
• High energy consumption
• Compressor failures
• Controls failures

Regular commercial HVAC maintenance can help you avoid many of these issues. If you're having trouble with your commercial air conditioning or heat pump cooling, contact a reliable commercial HVAC company for professional assistance.

For further guidance on maintaining your commercial HVAC system, consult maintenance resources or contact your local Trane representative for expert advice.