How a Cooling Coil Works

April 17, 2023

From typical office environments, to manufacturing plants, to schools, hospitals and other institutional buildings, cooling coils keep millions of people comfortable every day no matter how high outside temperatures climb.

They are also used in industrial process cooling applications to make some manufacturing processes possible and to optimize others. While they come in a wide range of types and sizes, all cooling coils use the same basic principles:

  1. Chilled water, liquid refrigerant or another fluid enters the coil and travels through a series of tubes which are connected to metal fins.
  2. As warm air blows across the cold tubes and fins, heat is removed from the air and transferred to the fluid.
  3. As the air temperature drops and the dew point is reached, moisture condenses out of the air. Condensate is carried to the bottom of the coil where a drain pan captures the liquid and directs it somewhere else – usually out of the system and into a drain.
  4. Cooler, typically saturated air then exits the coil. (In cases where the dew point isn’t reached, there may not be condensate to drain out of the coil, but the humidity ratio will be higher than the entering air. This is important to consider in any manufacturing process that is sensitive to humidity levels.)

Cooling coils can be broken down into two main types: standard fluid coils and refrigerant coils. Both achieve the same result of cooling incoming air, but are designed differently to accommodate the different cooling medium.

Standard Fluid Coils

Fluid coils used for cooling typically utilize chilled water or glycol/water mix (to prevent freezing) as the heat transfer fluid. At Marlo, we manufacture several different types of fluid coils for a wide range of applications, including standard coils, pitched core coils, coils with cleanable tube plugs, and coils with removable box headers. These coils are used in both comfort cooling and industrial process cooling applications.

Direct Expansion (DX) Coils

Direct expansion (DX) coils, also known as evaporator coils, use refrigerant to remove heat from the incoming air. The refrigerant enters the coil as a liquid, flows through the tubes and absorbs the heat from the warm incoming air, evaporating the refrigerant into a gas. The gas then flows from the evaporator coil to the compressor, where it is compressed to a higher pressure. From there, it flows through a condenser coil, where heat is removed and released into the outdoor air. The gas condenses back into a liquid and the process repeats.

As a custom manufacturer, we design and build each cooling coil to meet the specific requirements of its individual application. So, whether you want an exact replacement for an existing coil, or if you want to improve the performance of your HVAC system, your local Marlo representative can work with you to design the coil that will best meet your needs – including customizing the coil for the exact size, materials and any special features you may need.

You can read more about our wide range of coil products, or find your local Marlo representative.

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