Effect of condensing unit layout at building re-entrant on split-type air-conditioner performance

The use of split-type air-conditioners is popular in residential buildings of Hong Kong. In new apartment buildings, the building re-entrants are the most frequent choice of the project team for placing the outdoor condensing units. Nevertheless, the effect of heat dissipation from all condensing units at a re-entrant can be detrimental. Improper condenser layout incurs energy wastage, equipment de-rating and malfunction problems. Because of the continuing changes in outdoor air conditions, individual air-conditioner usage and loading, accurate prediction of the thermal impact at a re-entrant is virtually difficult. Based on computational fluid dynamics (CFD) analysis incorporating with an energy performance evaluation model, the effectiveness of various condenser layout schemes in building re-entrants under steady-state conditions was explored in this paper. It was found that there are limited hard-and-fast rules to give definite solutions. Provided that there is no physical access problem, an alignment of condensing units facing inward to induce a positive inflow of air into the re-entrant is a desirable solution.