The thermal contact resistance has been frequently neglected in the process of design of heat exchangers because of the difficulty of measurement and the lack of accurate data. However, the thermal contact resistance is one of principal parameters in heat transfer mechanism of fin-tube heat exchangers. The objective of the present study is to investigate new factors such as fin types and manufacturing types of the tube affecting the thermal contact conductance and to find a correlation between the thermal contact conductance and the effective factors in fin-tube heat exchangers with 7 mm, tube. The thermal contact conductances in the 22 heat exchangers with 7 mm tube have been investigated through the experimental numerical method. A numerical scheme has been employed to calculate the thermal contact conductance and the portion of thermal resistances using the experimental data. As a result, the thermal contact conductance has been evaluated quantitatively, and a new correlation including the influence of new factors such as fin types and manufacturing types of the tube has been developed in the fin-tube heat exchanger with 7 mm tube. Also, the portion of each thermal resistance has been evaluated in each case. (c) 2005 Elsevier Ltd. All rights reserved.