Enhanced Heat Transfer of Different-Mode-Interacting Boiling in Microchannel Flow Boiling

Due to the integration and miniaturization of electronic devices, their heat dissipation can exceed 10MW/m2, which is beyond the upper limit of a single-phase cooling scheme used in the current high-power systems;therefore, a new cooling scheme is urgently needed. One of the possible ways for overcoming the limitation of a single-phase heat transfer is to change it to the two-phase boiling heat transfer, where the critical heat flux (CHF) is the upper limit of the boiling heat transfer. Therefore, in order to improve the critical heat flux of flow boiling in a microchannel, non-uniform thermal conductivity plate was designed. Two types of materials with different thermal properties, copper and polytetrafluoroethylene, were alternately arranged inside the heat transfer plate near the surface to realize the non-uniform temperature distribution on the heat transfer surface and different-mode-interacting boiling, that is, the coexistence of nucleate boiling and film boiling. Also, a micro-channel flow boiling experimental system is built. In the experiments, the microchannel section size was 1. 84mm×70.00mm, the channel length was 280.0mm, the surface size of the heat transfer plate was 10.0mm×10.0mm, and the test fluid was deionized water. The effect of different-mode-interacting boiling types on the heat transfer enhancement during the flow boiling in a micro-channel was studied at different inlet velocities and subcoolings, which were v=0.1m/s, 0.2m/s, and 0.4m/s and DTsub=10.0K, 20.0K, and 30.0K, respectively. The results showed that the different-mode-interacting boiling could effectively enhance the CHF of flow boiling compared with the nucleate boiling. In addition, the inlet velocity and subcooling had a significant impact on the critical heat flux, and the trends were the same. Thus, the reduction in inlet velocity and subcooling could increase the ratio of critical heat flux enhancement. In the experiment, the largest ratio of critical heat flux enhancement was approximately 43. 4% at the inlet velocity of v=0.1m/s and subcooling DTsub of 10.0K. © 2020, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.