INVESTIGATION OF THE PERFORMANCE OF A SPIRAL-COIL FINNED TUBE HEAT EXCHANGER UNDER DEHUMIDIFYING CONDITIONSP. Naphon and S. Wongwises UDC 621.184.64 In the present study, heat-transfer characteristics of spiral-coil finned tube heat exchangers under dehumidifying conditions are investigated. A mathematical model of Ho et al. is modified by including fin efficiency. The derivation and solution methodologies are explained in detail. The effects of various inlet conditions of fluids flowing through the heat exchanger are discussed. The agreement of the model with the experimental data is satisfactory, with an average error of 1.2 and 4.0% for enthalpy and humidity effectivenesses, respectively. Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Laboratory (FUTURE), Department of Mechanical Engineering, King Mongkut's University of Technology, Thonburi, Bangmod, Bangkok 10140, Thailand. Tel.: +662-470-9115; Fax: +662-470-9111; email: firstname.lastname@example.org. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 76, No. 1, pp. 71-79, January-February, 2003.