Computational method for characterization of a microchannel heat sink with multiple channels involving two-phase flow

Two-phase microchannel heat sinks are of interest in electronics cooling because of their compactness and low thermal resistance. In this study, a computational method is presented for the analysis of conjugate heat transfer and two-phase flow in a heat sink containing multiple microchannels that have prescribed flow rates. It involves coupled analysis of conduction within the solid and simultaneous two-phase flow and heat transfer in the microchannels. The flow and thermal behavior in each microchannel is determined by solving the one-dimensional momentum and energy conservation equations. Coupling between the heat transfer within the solid region and the two-phase flow in the microchannels is handled through iterations involving the transfer of heat flux distributions on the channel bounding surfaces. The method has been applied for the prediction of the flow and thermal performance of a heat sink with equal mass flow through individual microchannels. The results of our analysis show the important physical effects in the two-phase flow regime, namely the acceleration pressure drop and the boiling enhancement of heat transfer, that strongly affect the relative behavior of the individual microchannels. The study demonstrates quantitatively that the disparity in the heat loads is the cause of flow redistribution among the microchannels. Finally, the computational method presented in this study enables determination of the flow resistances of individual microchannels for a prescribed flow distribution. When combined with a network-based approach, this method will enable the prediction of both the two-phase flow distribution and thermal performance of practical heat sinks containing multiple microchannels