A novel transient thermohydraulic model of micro-channel heat sink

•Novel transient thermal numerical model is presented for a single micro-channel heat sink.•Governing equations for the transient were derived under liquid thin-film evaporation.•Predicted performance variables were analyzed during the whole transient process.•The model was validate by experimental results in the literature.•Influence of the input variables on the transient simulation was investigated. The purpose of this work is to develop an analytical model for prediction of the thermal fluid performance of a micro-channel heat sink by applying liquid thin-film theory. For this purpose, a one-dimensional transient model has been developed for a single channel of micro-channel heat sink and a series of numerical simulation was performed for various operating conditions. Mass, momentum and energy equations were applied separately for the vapor and liquid phases to predict more effective physical performance of the transient behavior. As a result, the axial distributions of mass flow, pressure, and temperature for the working fluid were obtained for vapor and liquid in the micro-channel. In particular, the phase change interface profile with the liquid thin-film was obtained using an augmented Young Laplace equation. Consequently, the interface areas of heat and mass transfer occupied by the liquid and vapor were predicted and incorporated into the governing equations of each phase. The analytical model was validated by comparison of its numerical solutions with experimental results. The discrepancy between the experimental and numerical results for the axial wall temperature was less than 4 °C, and that for the transient time to reach a steady-state wall temperature was within 1 sec. Through a series of performance simulations for a micro-channel model with pure water as the working fluid, transient response of the wall temperature, liquid film thickness, mass flow rate, liquid pressure, and vapor and liquid temperatures were investigated. The model developed in this study might be utilized for more refined performance prediction of a micro-channel heat sink.