For a cooling tower, approach is leaving water temperature minus entering air wet bulb, often around 7 degrees F at design. For a chiller condenser, it is condensing temperature minus leaving condenser water temperature; for an evaporator, leaving chilled water minus evaporator saturation. A small approach means good heat transfer, and a creeping approach on a chiller is the classic sign of fouled tubes or low charge.
Condenser approach on chiller two is up to 6 degrees from 2, the tubes need brushing before summer.
Also heard as
- temperature approach
- approach temperature
Related terms
Chiller
A refrigeration machine that cools water or glycol, which is then pumped to coils to cool a building or process.
Cooling tower
Equipment that cools condenser water by evaporating a small part of it into an airstream.
Condenser
The heat exchanger where hot, high-pressure refrigerant gives up heat and condenses back to a liquid.
Wet bulb
The temperature a wet-wicked thermometer reads in moving air, lowered by evaporation in proportion to how dry the air is.