City University of Hong Kong Department Name



Split-type air-conditioner heat dissipation


The use of split-type air-conditioners has been growing in residential buildings of Hong Kong. In new apartment buildings, the building re-entrants are popular 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 mal-function problems. Because of the continuing changes in (i) outdoor air conditions, (ii) the individual air-conditioner usage, and (iii) the room loading, accurate prediction of the thermal impact at a re-entrant is highly difficult. Based on the Computational Fluid Dynamics analysis incorporating with an energy performance evaluation model, the effectiveness of various condenser layout schemes in building re-entrants was evaluated. The evaluation was extended to seek the alternative way of placing the condensing units in an air-conditioning plant room provided in individual domestic flat. The similar approach was used for predicting the condensing unit performance at the low-rise residences.


Array of condensing units at a building re-entrant

 กกAir temperature contours at one floor level of an L-shape re-entrant for different wind conditions



Alternative schemes of introducing condenser cooling airflow via light wells


Related publications :


Journal articles:

Chow TT, Lin Z. Prediction of on-coil temperature of condensers installed at tall-building re-entrant. Applied Thermal Engineering, Vol.19(2), 1999, pp.117-132.

Chow TT, Lin Z, Wang QW. Applying CFD simulation in analysing split-type air-conditioner performance at buildings. Architectural Science Review, Vol.43(3), 2000, pp.133-140.

Chow TT, Lin Z, Wang QW. Effect of building re-entrant shape on performance of air-cooled condensing units. Energy And Buildings, Vol.32(2), 2000, pp.143-152.

Chow TT, Lin Z. Provision of air-conditioning in apartment buildings of Hong Kong and the recent problems. International Journal for Housing Science and Its Applications, Vol.25(1), 2001, pp.13-21.

Chow TT, Lin Z, Wang QW. Flow analysis of condenser cooling air delivery via building light well. Applied Thermal Engineering, Vol.21(8), 2001, pp.831-843.

Chow TT, Lin Z, Yang XY. Numerical study of air flow and heat transfer at condensing units of split-type air-conditioners installed at low-rise residences. Journal of Refrigeration, Vol.1, 2002, pp.45-48. (in Chinese with English Abstract)

Chow TT, Lin Z, Liu JP. Effect of condensing unit layout at building re-entrant on split-type air-conditioner performance. Energy And Buildings, Vol.34(3), 2002, pp.237-244.

Chow TT, Lin Z, Liu JP. Effect of condensing unit operation on kitchen exhaust at residential tower. Architectural Science Review, Vol.45(1), 2002, pp.3-11.

Chow TT, Liu JP, Wang QW. Evaluating group performance of residential air-conditioners. International Journal on Architectural Science, Vol.3(2), 2002, pp.61-71.

Chow TT, Lin Z, Yang XY. Placement of condensing units of split-type air conditioners at low-rise residences. Applied Thermal Engineering, Vol.22(13), 2002, pp.1431-1444.

Conference papers:

Chow TT, Lin Z. Thermal problems of split-Type air-conditioning units installed at high-rise buildings of Hong Kong. Proceedings of ACHRB ’97, IIR International Symposium, Shanghai, China, September 1997, pp.108-113.

Chow TT, Lin Z, So ATP. Studying thermal effects on split-type air-conditioner operation in multi-storey buildings in Hong Kong. Proceedings of 32nd Annual Conference of Australian & New Zealand Architectural Science Association, Victoria University of Wellington, Wellington, New Zealand, July 1998, pp.163-169.

Chow TT, Lin Z, Wang QW, Lu JWZ. Studying thermal performance of split-type air-conditioners at building re-entrant via computer simulation. Proceedings of Building Simulation ’99, the 6th IBPSA International Conference, Kyoto, Japan, September 1999, Vol.3, pp.1357-1363.

Chow TT, Lin Z, Liu JP. Placement of air-cooled condensing units in multi-story apartments. Proceedings of the 4th International Congress of SITHOK: Heating & Air-conditioning for the Third Millennium, Maribor, Slovenia, May 2000. (CD ROM)

Chow TT, Lin Z, Fong KF, Liu JP. On the use of air-conditioning plant room to house condensing units of split-type air-conditioners in residential buildings, Proceedings of ROOMVENT 2000, Reading, UK, July 2000, pp.977-982.


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