In this study natural convection heat transfer of15 fin-tube heat exchangers was measured. There were five fin pitches and three different tube numbers. The results show that lower chilled water temperature will give more heat transfer, but water velocity in tubes is a weak factor of heat transfer. It was also found that the single-tube heat exchangers have the highest heat transfer coefficient, with the three-tube heat exchangers the lowest. The heat transfer coefficient and the unit area heat transfer rate of the heat exchangers can reach 10 W/m2 °C and 100 W/m2, respectively. A hydraulic diameter for fin-tube heat exchangers was defined and used as the length scale of natural convection heat transfer. The experimental results were analyzed and the correlation Nu = 0.43 (RA)0.25 was obtained.

Units: SI