Airflow maldistribution and the performance of a packaged air conditioning unit evaporator

Abstract

The performance of an evaporator for a packaged air conditioning unit has been investigated. A heat transfer program ACOL5 validated in an earlier study, was used to predict the performance. Non-uniform velocity distribution measurements taken in a typical air conditioning unit were employed in the prediction of the evaporator performance. It was found that this maldistribution reduced the performance of an evaporator circuit, as compared to uniform flow. Circuits at the edges of the evaporator, where the velocity was low, did not perform well. With the refrigerants controlled by one thermostatic valve, the worst performing circuit affected the performance of the whole evaporator, the evaporator performance being reduced by as much as 35%. The performance of the evaporator, where the circuits had different numbers of passes, depended on the position of the circuit in the evaporator.