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This paper experimentally investigated the impact of the electric field strength (E), electrode installation heights (H), and the electrode shape on enhanced pool boiling heat transfer performance under a downward heating surface with an electric field. It is observed that the critical heat flux (CHF) generally increases with increasing electric field strength. For instance, for the mesh electrode, the CHF is increased by 100.0%, 240.0%, 340.0%, and 440.0% at E = 0.35 × 106 V/m, 0.70 × 106 V/m, 1.05 × 106 V/m, and 1.40 × 106 V/m, respectively, compared to E = 0 V/m. Furthermore, the electrodes hinder the detachment of vapor bubbles, which becomes more pronounced when the electrode installation height is low. At the same time, the more micro-ribs of the electrodes and the denser the distribution, the more uniform the electric field generated. Under this condition, the “pinch-off effect” caused by the non-uniform electric field is reduced, which is more conducive to enhancing boiling heat transfer performance. Ultimately, at H = 5.0 mm and E = 1.40 × 106 V/m, the CHF with grid electrodes improved by 101.1% compared with the horizontally upward without the electric field, which is a superior combination of working conditions and suggests that a more optimistic boiling heat transfer performance can be obtained in microgravity. This work provides guidance for enhancing boiling heat transfer in microgravity by an electric field.

The uniformly distributed mini-pin-fins on the copper surface were designed and processed, and the enhanced boiling heat transfer performance on mini-pin-finned copper surfaces in FC-72 was investigated. The smooth copper surface was used as the experimental comparison group. The effect of the copper fin height, spacing, and width on the pool boiling heat transfer performance and the fin efficiency were investigated. At the same liquid subcooling, the critical heat flux and heat transfer coefficient of the uniformly distributed mini-pin-finned copper surface increased with the copper fin height, decreased with the rise of the copper fin spacing and fin width. The fin efficiency increases with the rise of the fin height, spacing, and width. The critical heat flux of the mini-pin-finned copper surface (PF0.3–0.2–2) reached 115.4 W·cm−2 at liquid subcooling of 25 K and increased by about 3.62 times compared with the smooth copper surface, and the heat transfer efficiency of mini-pin-finned copper surface (PF0.5–0.2–2) exceeded 95%.

The pool boiling heat transfer (phase-change immersion cooling) phenomenon holds significant importance in the energy consumption management of large-power electronics. However, the optimization of surface structure for achieving stable and efficient heat transfer during boiling process remains a significant challenge. Herein, we propose a simplified and direct hybrid surface strategy that combines crossed mini channels and a capillary wick to address the cooling issues faced by high-performance power devices. The copper capillary wick is combined with the crossed mini channel to form a hybrid surface by a simple integrated sintering method. This study investigates the combined effects of different parameters of the capillary wick (average diameter size and powder addition) and minichannels (depth and width) on enhancing the nucleate boiling performance on these hybrid surfaces. The working fluid used in this investigation is HFE-7100. At ΔTsub = 30 K, the CHF achieved by the hybrid surfaces combining capillary wicks and minichannels can reach 131 W/cm2, while the highest HTC is measured at 2.32 W/(cm2·K), both CHF and HTC achieve multiplicative enhancement compared to smooth surfaces. Furthermore, we have developed a CHF prediction model for the hybrid surfaces, which exhibits a prediction error of less than 15%.