New approach for performance testing of air-cooled condensing units

Condensing units are designed to work with the condenser-fan component working in open space. Testing condensing units in these conditions presents several drawbacks: difficulty to find a really infinite plenum and to avoid air shortcuts around the condenser inlet which means temperature variations, impossibility to measure the mass flow rate passing through the condenser. On the other hand, separating the condenser inlet and outlet plenums means a risk of not controlling the pressure difference between the two plenums and then overfeeding or underfeeding the condenser. This paper discusses the advantages and disadvantages to work in one way or in another. A method is presented to avoid condenser over or underfeeding and guarantee a low air velocity profile. Finally, an example of a flat-coil condensing unit tested with two different fans, variable refrigerant charge and evaporating temperature is shown to illustrate the discussion. (C) 2003 Elsevier Inc. All rights reserved.