Experimental Study on Dynamic Thermal Response Characteristics in a Microchannel Evaporator

As the heat flux of electronic devices continues to increase, conventional air cooling and single-phase liquid cooling technologies are increasingly constrained by heat transfer limits and pumping power consumption. However, systematic investigations on the coupling between microchannel evaporators and the overall dynamic response of MPTL systems remain limited. To address this issue, a visualization experimental platform for the microchannel MPTL was developed, and flow boiling experiments were conducted under varying heat fluxes and circulating flow rates. Key parameters including wall temperature, fluid temperature, pressure drop, and flow patterns were measured to characterize the thermal–hydraulic behavior of the system. The results show that the wall temperature increases stepwise with increasing heat flux, reaching a critical heat flux of 814.2 W/cm2 at a mass flux of 105.6 kg/(m2·s), where heat transfer deterioration occurs. During this transition, inlet temperature oscillations with an average amplitude of 8 °C were observed due to vapor backflow. With decreasing circulating flow rate, the flow pattern evolved sequentially from single-phase flow to bubbly, slug, churn, annular, and reverse annular flow, accompanied by a shift in the dominant heat transfer mechanism from forced convection to nucleate boiling and convective evaporation. The best heat transfer performance occurred under annular flow conditions at an outlet vapor quality of 0.4–0.5. These findings provide useful guidance for the design and operation optimization of microchannel MPTL systems in high-heat-flux electronic cooling applications.