Flow boiling heat transfer coefficients and pressure drops of FC-72 in small channel heat sinks

In this study, the heat transfer and pressure drop characteristics of FC-72 in small channel heat sinks, which were designed for liquid cooling of electronic components, were measured by varying the mass flux, saturation temperature, and vapor quality. The small channels had circular cross-sections with diameters of 2 and 4 mm and length of 100 mm. The heat flux provided by the heaters in the copper block ranged from 0.5 to 3.0 W/cm². Based on data comparisons, the existing pressure drop correlations were modified by introducing the effective viscosity including wall effects of the fluid in the small channel. The modified homogeneous pressure drop model yielded the best predictions with average and mean deviations of 0.9% and 27.0%, respectively. The measured heat transfer coefficient was also compared with the predictions obtained by using the existing heat transfer correlations. The Kandlikar correlation with the fluid surface parameter for water yielded consistent trends with the measured heat transfer coefficient. A new fluid surface parameter F_Fl = 0.747 for FC-72 was proposed based on the present data, and satisfactory predictions were obtained with average and mean deviations of 0.4% and 7.0%, respectively.