On the use of air-conditioning plant room to house condensing units of split-type air-conditioners in residential buildings

The developer’s provision of split-type air-conditioners to residential buildings is growing popular in Hong Kong. So far the building re-entrant is one most common location for placing the outdoor condensing units. In a high rise residential building, it is not surprising to have over a hundred of these condensing units being installed within one single re-entrant. The rejected energy and the thermal plume then formed can result in very unfavorable air-cooling environment. The consequence can be a significant degradation in air-conditioner performance and a waste of electrical energy, especially for those units at the upper floor levels. An alternative way of placing the condensing units is by providing an air-conditioner plant room to each apartment to house the condensing units of its own. Condenser cooling air is led into the plant room through an intake louver at one external wall and discharged through openings at another wall. This minimizes the thermal effect, and is expected to result in much better air-conditioner performance than by placing the condensing units at the re-entrants. This paper examines the new concept through the use of CFD analyses. Alternative arrangements are discussed.