The Condenser is one of the Four main Components of Refrigeration and Air Conditioning. The other three Components are the Evaporator, Compressor, and Metering Device.
The Condenser’s job is to dissipate both the heat absorbed in the Evaporator and the heat gained in the Compressor during compression.
In the refrigeration cycle, superheated refrigerant vapor enters the Condenser from the Discharge Line. The Condenser then performs three primary functions:
- De-superheating: Cooling the superheated vapor to its saturation temperature
- Condensation: Changing the refrigerant from vapor to liquid state while maintaining constant temperature and pressure
- Subcooling: Further cooling the liquid refrigerant below its condensing temperature
Note: Subcooling (at the Condenser’s outlet/Liquid Line) increases Refrigeration Effect, helps mitigate Flash Gas, and assists in providing a full column of Liquid Refrigerant to the Metering Device.
Condensers usually have their Refrigerant inlet physically at their top from the Discharge Line and have their outlet at the bottom to the Liquid Line or Condensate Line (for systems that employ Receivers). Some Condensers, however, have their inlet at the bottom, side, or other orientation to assist with equal Condenser circuit distribution.
Condenser Accessories
To assist with Condenser Operation, there are different accessory devices that are commonly used to help regulate its operation. The target with any type of Condenser control is maintaining the system’s intended Condensing Pressure.
Condensers often employ a fan, and methods to control this include Fan Cycling Controls, and Variable Speed Drives or ECM’s (Electronically Commutated Motors). Condenser fans can also simply be on/off. Condensers may have a single fan or multiple which can be staged.
To assist with maintaining sufficient Condenser Pressure during varying loads and reduced Outdoor Ambient Temperature during Winter in cold climates, Air Louvres, or Condenser Flooding Valves may be used.
Note: Condenser Splitting is a method used in Supermarket Refrigeration that utilizes “Valving” to split the Condenser’s physical size based on load and ambient conditions.
Condensers that are Liquid Cooled can utilize a spring-actuated “Water” Pressure regulator to vary the flow of the Condenser Cooling Medium to maintain Head Pressure.
Air-Cooled Condensers
Air-Cooled Condensers employ Ambient Air (usually outdoor air), which is at a lower temperature than the temperature at which the Refrigerant Condenses. Air-Cooled Condensers often have a fan to assist with increasing the heat transfer rate.
Note: all types of Condenser Coils may be manufactured from Copper, Aluminum, Steel, or Stainless Steel, depending on their application.
Natural Convection
The Condenser on most home fridges is a Natural Convection Air-Cooled Condenser, which does not use a fan to expedite heat transfer. With not too much heat to get rid of, applications like this are a good candidate for manufacturers to save costs on a part, while eliminating the potential failure of a fan motor.
Note: on Domestic appliances, Condensers may be bare tubes joined to thin steel wires. The wires stabilize the coil and increase its Surface Area.
Forced Convection
Forced Convection is by far the most common type of Air-Cooled Condenser. It can utilize a single or multiple fans, which can be controlled by the methods mentioned above in “Condenser Accessories”. Note: Forced Convection Condensers almost always have their tubes joined to Fins, which increases their surface area. The increased surface area allows for better heat dissipation from the coil. The article’s first image and the image below both show Condensing Units which utilize Finned Tubes on their Condensers.
Water-Cooled Condensers
Water-Cooled Condensers have the benefit of being cooled by “Two Mediums”: water and air. Depending on their Construction, water usually transfers its energy somewhere “Inside” of the refrigerant passage, while the surrounding air allows heat transfer on the “Outside” surface of the refrigerant.
Note: instead of water, any Water-Cooled Condenser could instead be cooled with Glycol, depending on the application.
Coaxial Tube-in-Tube
The Tube-in-Tube part of this name refers to the Water Coil being physically inside the Refrigerant Coil. The air surrounding the Refrigerant Coil’s ambient provides additional heat transfer for the Condenser. The Coaxial part of this Condenser’s name comes from the Water Coil following the Refrigerant Coil on the same axis. These are commonly run in a circular shape and installed on smaller Condensing Units. Their application is often for systems which serve Low Temperatures, and are required to rid much Enthalpy from a high Heat of Compression.
Note: most Water-Cooled Condensers use “Countercurrent Flow”. The Refrigerant and Water will flow in opposite directions to maximize heat transfer.
Plate Condensers
Plate Condensers have a large number of channels where there is heat exchange between the refrigerant and the water. This Condenser type is also known as a brazed plate heat exchanger (BPHX).
When charging refrigeration systems with plate condensers, special care must be taken to avoid freezing the heat exchanger.
Shell and Tube Condensers
Large-capacity condensers typically found in chillers, featuring a cylindrical shell holding liquid Refrigerant, which surrounds the Condenser’s Tubes. The Tubes are filled with water, which flows in and out of the chiller. The usual way in which this “Condenser Water” is cooled is with a Cooling Tower (an accessory to this Water-Cooled Condenser).
Note: a Shell and Tube Condenser also functions as a refrigerant Receiver, with its large capacity to store Liquid Refrigerant.
Other Condenser Types
Evaporative Condensers
Evaporative Condensers are a hybrid between Air and Water-Cooled condensers. They are unique in that both the air and water are cooling the Refrigerant Condenser from its outside. The image below shows both existing and mid-construction (on the right: not yet tied into the system) Evaporative Condensers. The Refrigerant Piping’s inlet is at the top, and its Condensate Drain is at the bottom (yellow on the left). The Water Inlet is at the top (in green on the left) and feeds spray nozzles to distribute the water over the coil. This water partially Evaporates as it falls, which assists with its cooling effect. The water collects in the “Sump” at the Condenser’s bottom, and follows a drain pipe back towards the Condenser Water Tank and Condenser Water Pump.
This Condenser type often employs a fan to assist in heat transfer. Their common application is Ammonia Systems. This evapco Piping Guide offers more information on Evaporative Condensers (this article’s second image is from this document).
For more detailed information on evaporative condensers in industrial applications, refer to the HVAC Know It All podcast episode on industrial refrigeration.
Adiabatic Condensers
Adiabatic Condensers are commonly used on CO2 systems. Since CO2’s Refrigerant States are unique, this Condenser may instead function as a Gas Cooler depending on outdoor and system conditions.
The Adiabatic Condenser is unique in utilizing a Wetted Pad to “Pre-Cool” the entering air. This gives the Condenser function an added efficiency while allowing good results in high ambient conditions. Further details can be found in evapco’s product guide for their Adiabatic Condensers.
These systems are becoming more common in commercial refrigeration applications, particularly in supermarket installations.
Glycol-Cooled Condensers
Instead of water, a Refrigerant Condenser may be cooled by Glycol. Since Glycol has a lower rate of heat transfer compared to water, the use of a Glycol-Cooled Condenser occurs for sites with limited availability of water supply.
After serving the Condenser (usually indoors), the Glycol will be pumped to a Dry Cooler (usually outdoors) to allow the Glycol to cool down in a coil that is commonly of a finned type, and assisted by fans.
Note: depending on the manufacturer, Dry Coolers may instead be referred to as Fluid Coolers.
Common Types Of Condensers
Common Types Of Condensers include:
- Traditional copper coil with aluminum fins
- Micro Channel Condenser
- Condenser Bundle
- Coaxial Coil
- Brazed Plate Heat Exchanger
Microchannel condensers represent one of the most significant advancements in condenser technology, featuring multiple flat tubes with small channels for improved heat transfer efficiency and reduced refrigerant charge requirements.
Practical Applications and Maintenance Considerations
Proper condenser maintenance is essential for system efficiency and longevity. Key maintenance tasks include:
- Keeping air-cooled condenser coils clean and free of debris
- Ensuring adequate airflow around the condenser
- Maintaining proper water treatment for water-cooled systems
- Monitoring subcooling to verify proper condenser operation
- Checking for non-condensable gases that can reduce efficiency
Proper condensate management is also critical, particularly in high-humidity environments where condensation rates are significant.
Summary
Condensers, in basic principle, are a simple Component of the Refrigeration System. There are, however, many different types, so it is helpful to be knowledgeable of this when working on a variety of equipment. Awareness of unique Condenser applications assists in setting up to perform Service, Maintenance, and Construction on Refrigeration and AC Systems.
For hands-on professionals, developing expertise in condenser technology is critical as we continue to see advancements in HVAC technology and efficiency standards.