Recently, due to the global warming caused by the green house effect of various gases, the need of refrigeration and air-conditioning has been increased day by day. Increasing the efficiency of the refrigeratiion and air-conditioning system could reduce the electrical power consumption directly. The objective of present study is to apply the swirl atomizer to spray fine droplets on the composite heat exchangers, in order to perform an investigation on the controlling parameters associated with the droplet diameter, the forced convective effect, the changes in the types of the heat exchangers, and the effect on the over all heat transfer rate. Optimal operating conditions adapt to the refrigeration and the air-conditioning system is to be found. According to the experimental results, the simultaneously effects of evaporation cooling with smaller spraying droplets and forced convection cooling could significantly enhance the heat transfer efficiency of the composite heat exchangers. But with no fan operating for forced convection, the heat transfer efficiency of spraying with the large droplets is better than the one with the small droplets. The efficiency of forced convection is better than spraying droplets when each one is operated alone. In conclusion, applying swirl atomizers to the composite heat exchanger could provide pronounced enhancement on its heat transfer efficiency.