Numerical Modeling of Pressure Drop and Pump Design for High Power Density Microchannel Heat Sinks With Boiling

A physical and mathematical model has been developed to predict the two-phase flow and heat transfer in a microchannel with boiling. Based on the above physical model, a total of seven unknowns with corresponding equations resulted. The liquid film thickness, the vapor pressure and the axial heat flow rate have been solved using a fourth-order Runge-Kutta method. The liquid pressure, the vapor and liquid temperatures have been solved using the finite difference method with first order accuracy. The interfacial temperature and pressure have been solved using the root finding method for every mesh point in the axial direction. In addition to the sample calculations that were used to calibrate the model, computations based on the current model were performed to generate results for comparison with Carey’s macro-scale model (Carey, 1992) and with the experimental data of Jiang et al. (2002) where three different mass flow rates of the working fluid were used in the experiment. The comparisons of pressure drops were made for 25 W, 38 W and 58 W of heating with mass flow rates of 2 ml/min, 5 ml/min and 9ml/min, respectively. In general, Carey’s model underpredicted the experimental data by Jiang et al. (2002), especially at the lower flow rates. The calculated results from the current model matched closely with those of Jiang et al. (2002). The main reason for the poor performance of Carey’s model is that it was developed for the macrosystems, where the surface tension and the Marangoni effects are not important.