Air cooled chillers are preferred in commercial buildings and industrial facilities because they do not rely on large water systems for cooling. For facility managers, engineers and procurement teams, it is good to understand how such systems work to help solve energy efficiency, maintenance and performance issues.
This article describes how air cooled chillers work and help you select the appropriate design for your requirements.
What Are Air Cooled Chillers?
Air cooled chillers are cooling machines which are used in buildings and industrial facilities. They cool water and force the cold water through pipes to cool rooms, equipment or production processes.
Main Components of Air Cooled Chillers
a) Compressor
The compressor circulates refrigerant within the system and maintains the cooling cycle. It absorbs refrigerant in the form of low pressure gas and compresses it into high pressure gas. This difference of pressure enables the heat to exit the system.
b) Evaporator
The evaporator is used to extract heat out of water or process fluid. When warm water passes through the unit, the refrigerant absorbs the heat and starts boiling at a low temperature. This process cools the water and feeds it back into the system. Simultaneously, the refrigerant transforms into a gas, which ensures the efficient movement of heat and maintains the temperatures during cooling.
c) Condenser
The condenser transfers the heat from the refrigerant to outside the air. The hot refrigerant gas is introduced into the condenser where the fans blow air over the coils. Once the heat is released from the refrigerant, it transforms back to a liquid state.
d) Expansion Valve
The expansion valve dictates how much refrigerant enters the evaporator. Before cooling, it reduces refrigerant pressure and temperature. This process makes the refrigerant absorb the heat quickly.
How Air Cooled Chillers Work
Air cooled chillers use a closed loop process to cool water. This cycle is repeated continuously to maintain water at a constant cooling temperature. Every step relies on the previous one, thus effective process is important at all phases.
· Evaporation
Cooling starts within the evaporator. Warm water in your building or equipment is pumped through pipes in this unit. Simultaneously, refrigerant is introduced to the evaporator at low pressure and low temperature.
As the warm water flows through, heat is transferred between water and refrigerant. This heat causes the refrigerant to boil and transform into a gas. Since heat exits the water, the water temperature is lowered. The cooled water is then pumped back to air handling units or machines which require to be cooled.
At this phase, the temperature of the water usually drops to approximately 6°C to 7°C. Regulated water flow ensures that the cooling is always consistent and avoids the fluctuation in temperature.
· Compression
The refrigerant gas is forced out of the evaporator and into the compressor. The compressor squeezes this gas and increases its pressure and temperature. This process prepares the refrigerant to remove heat outside the building.
When the pressure increases, the refrigerant gets significantly hotter compared to the air outside. Normal discharge temperatures lie between 70°C and 100°C. This difference in temperature enables release of heat in the subsequent stage.
The compressor is also responsive to cooling demand. The compressor works more when more cooling is required. When less cooling is needed it decreases its workload. This response assists in managing energy consumption and stability of the system.
· Condensation
This hot and high pressure refrigerant gas then flows to the condenser and outdoor air is drawn over the condenser coils by fans. Since the refrigerant has more heat than the surrounding air, heat is removed out of the refrigerant and into the air.
The refrigerant is transformed back into a liquid as heat is removed. This is referred to as condensation. The air which passes through the condenser transfers the heat out of the system and dissipates it into the environment.
This stage is directly dependent on outdoor temperature. Hot weather complicates heat removal, increasing the pressure of the system and energy consumption.
· Expansion
After exiting the condenser, the refrigerant goes through the expansion valve. This valve decreases the refrigerant pressure abruptly. When the pressure decreases, so does the temperature.
The refrigerant exits the valve as a cold liquid-gas mixture. This condition prepares it to reabsorb heat within the evaporator. Depending on the cooling needs, the valve regulates the amount of refrigerant entering the evaporator.
When the cooling demand increases, more refrigerant is passed through the valve, while less refrigerant gets in when demand decreases. This regulation keeps the water temperatures constant and prevents system overload or inefficient cooling.
· Cycle Repeats
After expansion, the refrigerant is pumped back into the evaporator and the cycle repeats. This process is repeated as long as cooling is required.
Temperatures, pressures and water flow through the system are monitored by sensors. Control panels regulate compressor speed, fan operation and refrigerant flow to ensure a consistency in performance. This coordination guarantees effective cooling, regulated energy consumption, and extended equipment life.
Comparing Types of Air Cooled Chillers
| Type | Characteristic/working principle | Capacity | Best for |
| Scroll chillers | Compress refrigerant with a simple design using interlocking scrolls | Up to 150 tons | Small commercial buildings |
| Screw chillers | Use twin rotating screws to ensure continuous compression and steady output | 100 to 600 tons | Industrial processes |
| Centrifugal chillers | Higher speed impellers are used to increase refrigerant velocity and pressure | 300 tons and above | Large campuses |
| Modular chillers | Integrate several small units into a single system | 30 to 300 tons | Expanding facilities |
| Portable chillers | Air cooled condensers with self-contained units | 1 to 80 tons | Temporary cooling |
FAQs
What are the advantages of air cooled chillers?
Air cooled chillers are easy to install, require less water and less maintenance requirements thus they are suitable in areas where there is a scarcity of water.
What are the limitations of air cooled chillers?
Air cooled chillers cannot operate efficiently in hot climates, and they produce a lot of noise.
How do air-cooled chillers differ from water-cooled chillers?
Air cooled chillers reject heat using air and fans whereas water cooled chillers reject heat using cooling towers and water circulation.
What are best routine maintenance practices for an air cooled chiller?
Routine maintenance practices involve cleaning condenser coils, checking refrigerant levels, checking electrical connections, observing pressures and adequate airflow to maintain efficiency and prevent wear on components.
How do you determine air cooled chiller efficiency?
Efficiency is determined using metrics such as COP or EER, calculated by comparing cooling output and the electrical input at normal operating conditions and at certain ambient temperatures.
Chillerone is your Trusted Air Chiller Manufacturer in China
At Chillerone, we design and manufacture a wide range of air cooled chillers ranging from packaged chillers, modular chillers, to portable chillers. Our engineers will customize every chiller to your system’s cooling requirements.
Whether you want our standard chillers, or cooling systems designed to your unique specifications, Chillerone is your trusted partner in China – Contact our sales team for quotation.
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