Evaporative condenser
Also known as: water-spray condenser
Short definitionA condenser whose tubes are wetted with water while air is blown across them. The evaporating water carries the heat away; condensing temperature falls markedly compared with an air-cooled condenser.
In an air-cooled condenser the condensing temperature is 10–15 K above the outside air; on a 35 °C day that makes 45–50 °C. In an evaporative condenser, condensing approaches the wet-bulb temperature of the outside air and, when the air is dry, stays well below that figure. Each 1 K drop in condensing temperature cuts compressor consumption by roughly 2–3%.
It is used in ammonia plants, large central systems and cold stores in hot climates. In a dry climate the wet-bulb temperature is low, so the gain is greater. The price is water consumption, scale and water quality monitoring, frost protection in winter and Legionella precautions; these go into the operating cost. At small and medium capacities, the simplicity of an air-cooled condenser wins out. Adiabatic pre-cooling with wet pads is a halfway solution.