Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

In this paper, the forced convective heat transfer of FC-72 was experimentally investigated for various of parameters like velocity, inlet temperature, tube size, and exponential period of heat generation rate. Circular tubes with different inner diameters (1, 1.8 and 2.8 mm) and heated lengths (30–50 mm) were used in this study. The experiment data suggest that the single-phase heat transfer coefficient increases with increasing flow velocity as well as decreasing tube diameter and ratio of heated length to inner diameter. The experiment data were nondimensionalized to study the effect of Reynolds number (Re_d) on forced convection heat transfer. The results indicate that the relation between Nusselt numbers (Nu_d) and Re_d for d = 2.8 mm show the same trend as the conventional correlations. However, the Nu_d for d = 1 and 1. 8 mm depend on Re_d in a different manner. The conventional heat transfer correlations are not adequate for prediction of forced convective heat transfer in mini channels. The heat transfer correlations for FC-72 in vertical small tubes with diameters of 1, 1.8 and 2.8 mm were developed separately based on the experiment data. The differences between experimental and predicted Nu_d are within ±15%.