Experimental investigation and correlation analysis of pool boiling heat transfer on the array surfaces with micro-fins using FC-72 for the electronic thermal management

Pool boiling heat transfer characteristics were investigated on the both homogeneous and fractal array micro-pin-finned surfaces using FC-72 as working fluid. Two distinct fractal geometry pattern surfaces (Array4 and Array9) were designed to further explore their boiling heat transfer performance. The effect of different subcoolings (0 K, 15 K and 25 K) has also been analyzed combining fractal array surfaces. Bubble dynamics were captured using a high-speed camera. The results present the the array micro-pin-finned surfaces with less heat transfer area ratio can achieve similar or even higher CHF compared to the uniform micro-pin-finned surface (PF0.3–0.2–2), especially for subcooled boiling (ΔT_sub = 25 K). Notably, bubbles nucleate and grow prior to reaching the micro-pin-finned unit region. This phenomenon is evident in visual images, indicating that the fractal array effectively impedes bubble coalescence, particularly during subcooled boiling. Besides, this fractal array surface can provide liquid supply channels and prevent dry-out. The mechanism behind the heat transfer enhancement and CHF triggering is elucidated based on liquid replenishment and bubble coalescence behaviors. A CHF prediction model was established considering the effect of liquid subcooling, rectangular array distribution, and micro-fins feature size. And the prediction results from this model show well agreement with experimental values and data points from literature, with mean absolute deviation being less than ± 15 %.