In this study the effects of fin size, length of the evaporator, fluid velocity and heat pipe characteristics are investigated on the overall performance of heat pipe heat exchanger by thermal resistance analysis. The experimental device consist 19 stainless steel-water heat pipes with an outside diameter of 6.2 mm, a wall thickness of 0.5 mm and a length of 300 mm. The experiment was conducted at conditions for which hot gas and cooling waters enter at temperatures of 150-250ºC and 30ºC, respectively. The flow rate of gas through the evaporator is at the range of 0.114-0.270 kg/min, while the flow rate of water through the condenser is 0.940 kg/min. The length of the evaporator is twice the length of condenser in heat exchanger for better efficiency. The error between the theoretical and experimental result is 18.6-23.0 %.