Abstract: Fin-and-tube heat exchangers are widely used in refrigeration and air-conditioning appliances. Using smaller diameter tubes may help to improve the heat transfer performance and to decrease the size and the cost of the heat exchanger. In this paper, the state of art of fin-and-tube heat exchangers using small diameter tubes is reviewed. The reason of using small diameter tubes in fin-and-tube heat exchangers is elaborated, and the advantage of using small diameter tubes is qualitatively analyzed. The effects of small diameter tubes on the performance of air conditioner and on manufacture of fin-andtube heat exchangers are presented. The design of the new type of fins and the new type of distributor for fin-and-tube heat exchangers using small diameter tubes are illustrated. At last, the paper summarizes the development method of air-conditioning system using small diameter tubes.

Key words: Air conditioner, Fin-and-tube heat exchanger, Small diameter tube, Fin, Distributor