Adiabatic condensers and fluid coolers: Impact of pad system design on saturation efficiency and unit operation.

Refrigerant condensers and closed circuit coolers which utilize air-cooled heat exchange are growing in popularity for various reasons, but mainly to conserve water. However, in climates with high ambient temperatures, air-cooled heat exchangers require too much capital cost, consume too much energy and/or require too much plan area. In many cases, incorporating adiabatic pads on an air-cooled heat exchanger (a.k.a., an adiabatic fluid cooler or refrigerant condenser) is the best solution to balance costs, energy consumption and the size or number of units required. The adiabatic pad test program included testing ten pad designs from four adiabatic pad suppliers. The independent research contained in this report is offered for the benefit of industry, and to de-mystify some of the variables surrounding adiabatic cooling technology which have been misrepresented in the marketplace. The adiabatic air pre-cooling system uses water to depress the ambient air dry-bulb to a lower value, reducing the necessary size of the heat exchanger compared to a 100% air-cooled equivalent. Main conclusions: Saturation efficiency changes with air velocity. The maximum saturation efficiency achieved for the various adiabatic pads in this test program was: 78% at 2.0 m/s, 76% at 2.5m/s, 74% at 3 m/s and 72% at 3.5m/s. Saturation efficiency and air side pressure drop are equally important in rating the thermal performance of an adiabatic unit. Furthermore it was proven that water flow rate and water temperature have very little impact on adiabatic pad saturation efficiency when measured on a full-size adiabatic fluid cooler or condenser.