The purpose of this study is to build an experimental set-up which the performance test of heat exchangers are performed and to have a database about the heat exchangers having different geometry. The experimental set-up had been designed to find out heat transfer coefficients and friction factors of finned-tube heat exchangers for both cases of dry and wet surfaces. Under dry conditions, the air-side heat transfer coefficients and the friction factors of three finned-tube heat exchangers having different geometry were found out. Heat transfer coefficients of finned-tube heat exchangers are depend on the heat exchanger geometry and Reynolds number. While Reynolds number increases, the heat transfer coefficient decreases. As the fin spacing, which was the variable parameter in the experiments, decreases, heat transfer coefficient decreases, too. The friction coefficient of finned-tube heat exchangers are also depend on heat exchanger geometry and Reynolds number. In the same way, friction coefficient decreases, when Reynolds number and fin spacing increases. (C) 2002 Elsevier Science Ltd.