What is an Adiabatic Cooling Tower?
An adiabatic cooling tower is a hybrid cooling system that uses the adiabatic cooling effect of water evaporation to pre-cool the air before it passes over a heat exchanger. This dramatically increases the efficiency of the main heat rejection process.
Its key feature is that it combines the principles of a dry cooler (with a closed circuit) and the evaporative cooling of a wet cooling tower, but it uses water much more sparingly than a traditional wet tower.
How It Works (Step-by-Step)
Imagine a standard “dry” air-cooled heat exchanger (like a car radiator). Its cooling capacity is limited by the ambient dry-bulb temperature. An adiabatic system supercharges this process:
- Pre-Cooling Pad Section: The warm, dry ambient air first enters a saturated cooling pad at the air inlets. A pump circulates water over these pads, thoroughly wetting them.
- Evaporation and Adiabatic Cooling: As the air is drawn through the wet pads, a small portion of the water evaporates. This evaporation process absorbs heat from the air itself, cooling it down significantly. The temperature of the air drops closer to the wet-bulb temperature (the lowest temperature that can be reached by evaporating water only).
- Heat Exchange: This now pre-cooled and more humid air passes over the finned-tube heat exchanger coils. Inside these coils is the process fluid (water or a water-glycol mix) that needs to be cooled.
- Efficient Heat Rejection: Because the air is now much cooler than the ambient air, it can absorb far more heat from the process fluid inside the coils. The heated, moist air is then exhausted from the tower by a fan.
Water Usage: The water system that wets the pads only operates when needed (typically when the ambient temperature rises above a certain setpoint). When not needed, the
unit can run in a 100% “dry” mode, using zero water. This makes it highly efficient in both hot and cold weather.