What is meant by Evaporative Fluid Cooler?
An Evaporative Fluid Cooler uses this exact same principle of evaporative cooling, but it’s a mechanical system designed to cool a liquid (usually water or a water-glycol mixture) instead of a human body.
Formal Definition
An Evaporative Fluid Cooler (often used interchangeably with Closed-Circuit Cooling Tower or Fluid Cooler) is a heat rejection device that uses the evaporation of water to lower the temperature of a process fluid that is contained in a closed coil, preventing it from being exposed to the outside air or evaporating itself.
The key distinction is that the process fluid being cooled is separated from the water being evaporated.
How It Works: The Two Separate Circuits
This is the most important concept to understand. An evaporative fluid cooler has two completely independent circuits:
1. The Closed Process Fluid Circuit (The “What” is being cooled)
- This is the fluid that needs to be cooled. It could be:
- Water from a chilled water system in a building.
- Water-glycol mix from an industrial process (e.g., plastic moulding, laser cutting, power generation).
- Refrigerant from a condenser loop.
- This fluid is never exposed to the atmosphere. It flows through a sealed coil (usually copper or stainless steel) inside the cooler.
2. The Open Water Circuit (The “How” it is cooled)
- This is the evaporative part of the system.
- A pump circulates water (called recirculating water) from a basin at the bottom of the unit and sprays it over the outside of the closed coil containing the hot process fluid.
- Simultaneously, a large fan at the top of the unit draws ambient air through the falling water and over the coil.
- A small portion of this recirculating water evaporates into the air. The energy (heat) required for this evaporation is drawn from the closed coil.
- By stealing heat from the coil, the evaporation cools the process fluid inside the coil.
- The excess water that doesn’t evaporate falls back into the basin to be recirculated again.
Because of evaporation, minerals in the water become concentrated. To control this, a bleed-off valve (blowdown) drains a small portion of the dirty water, and a float valve makes up the loss with fresh water (make-up water).