How Does a Free Cooling Chiller Work?

External Free Cooler View

A free cooler, also known as a dry cooler, is a type of cooling system that uses ‘free’ outside air to cool the process fluid in a heat exchanger. Here’s how it works:

  1. The hot process fluid, typically water or a water-glycol mixture, is pumped through a heat exchanger, also called a “coil”, which is located outdoors.
  2. As the process fluid flows through the coil, a fan blows ambient air across the coil. This causes the heat from the process fluid to transfer to the air. Usually, a minimum difference of 10°F (~5°C) is enough.
  3. The process fluid is then pumped back into the facility to cool the equipment or process it is intended to cool.

Why use a free cooler system for your chilling process?

In a free cooler, the process fluid is cooled by the ambient air instead of a refrigeration cycle, which means that the system is more energy-efficient and less expensive to operate than traditional chillers. However, its performance is often limited by the outdoor temperature and humidity, and it may not be suitable for applications that require low process fluid temperatures.

What is the difference between a free cooler and a chiller?

A free cooler and a chiller are both types of cooling systems, but they operate in different ways and are used for different applications.

A chiller is a refrigeration system that removes heat from a process fluid and transfers it to a coolant/chiller fluid, typically water or a water-glycol mixture. The refrigerant then flows through a compressor, where it is compressed, and its temperature and pressure raised. The hot refrigerant gas is then condensed in a heat exchanger, releasing the heat it has absorbed. The now-cooled refrigerant is then expanded and passed through an evaporator, where it absorbs heat from the process fluid, completing the refrigeration cycle. Chillers, or also known as water cooled chillers, are typically used for large-scale cooling applications, such as air conditioning for commercial buildings or process cooling for industrial applications.

A free cooler, on the other hand, uses outdoor air to cool the process fluid in a heat exchanger or air-cooled coil. As mentioned earlier, the hot process fluid is pumped through a coil located outdoors, and a fan blows ambient air across the coil, which cools the process fluid. Free coolers can be used in all cooling applications, such as cooling for plastic injection molding, food, pharmaceutical, chemical, data centers or any other industrial processes that require cooling. 

In summary, while both free coolers and chillers are used for cooling applications, a chiller is a refrigeration system that uses a refrigerant to remove heat from a process fluid, while a free cooler uses ambient air to cool the process fluid.

Internal View of Free Cooler

Can you combine a free cooler and a chiller into one unit?

Yes, it is possible to combine a free cooler and a chiller into one unit, which is commonly referred to as a hybrid chiller.

A hybrid chiller is a cooling system that incorporates both a chiller and a free cooler in a single package. The system is designed to take advantage of the free cooling potential of the ambient air when the outdoor temperature is low enough to provide sufficient cooling, and to switch to mechanical cooling when the outdoor temperature rises.

In a hybrid chiller, the free cooling mode is typically achieved by using a three-way valve that diverts the process fluid through the free cooling coil when the outdoor temperature is lower than the process temperature setpoint. When the outdoor temperature rises above that setpoint, the valve switches back to the mechanical cooling mode, and the chiller compressor is turned on to provide additional cooling.

Hybrid chillers are often used in applications where the cooling load varies throughout the day or year, such as data centers or industrial processes with intermittent cooling requirements. By incorporating both free cooling and mechanical cooling capabilities into one unit, hybrid chillers can provide energy-efficient and cost-effective cooling solutions, while maintaining precise temperature control.

Free Coolers from Delta T Systems

Delta T Systems has recently launched a line of free coolers and has been an industry leader in chillers and temperature control system manufacturing. All of our products are designed and built in the USA. Our systems have been applied in a broad range of industries and applications, and our custom TCU and Chiller design continues to be used in a wide range of industries.

Our new free coolers and engineering capabilities have put our systems in the forefront of green temperature control technology by providing state of the art controls and the lowest energy consumption available in the industry. Our commitment to sustainability, efficiency and customer service is the reason clients continue to return to us time after time for new applications.

Learn more about Delta T Systems range of air and water-cooled chillers and temperature control units, contact us today!