Abstract:

Based on a self-induced jet impingement device designed for practical pool boiling enhancement, using R1336mzz(Z) as the working fluid, an experimental and parametric study in pool boiling performances on microporous copper surfaces with this device are performed, considering the fabricated characteristics of these surfaces such as particle size and ratio of thickness to particle size during sintering process. The results demonstrated that, due to the ensuring of sustained liquid absorption and the promotion of bubble detachment, the self-induced jet impingement device augmented the critical heat flux (CHF) on the microporous copper surface effectively. Nonetheless, the boiling suppression effect brought by the liquid jet impingement resulted in a minor decrease in heat transfer performance and its intensity was positively correlated with particle size, and is negatively correlated with ratio of thickness to particle size. Parametric evaluations indicated that boiling heat transfer performance increased with enlarging in particle size and initially rises with the increasing ratio of thickness to particle size before declining. The wickability of the microporous copper surface enhanced as both the particle size and the ratio of thickness to particle size increased. Generally, despite of the presence of a self-induced jet impingement device, wickability maintained a positive linear relationship with CHF. Nonetheless, at a particle size of 101μm, the self-induced jet impingement device exacerbated the wetting disadvantage due to inadequate capillary force, resulting in a reduced CHF. Our study indicated CHF and h_NB@CHF enhancements of up to 189.2% and 337.5%, culminating in CHF=72.0W/cm² and h_NB@CHF=87.5kW/(m²·K), respectively, compared to the boiling performances of standard pool boiling on the non-microporous copper surface.

Key words: heat transfer, phase change, pool boiling, dielectric liquid, sintering, porous media

摘要：

为强化池沸腾性能，本文基于一种适用于实际池沸腾强化的自驱射流冲击装置，使用R1336mzz(Z)作为工质，微多孔铜表面为加热表面，实验研究了自驱射流装置对沸腾性能的影响，并参数化研究了微多孔表面制备特征对池沸腾性能的影响，如烧结过程中的铜粉粒径尺寸（43μm、66μm、101μm）以及微多孔层厚度与粒径尺寸之比（4、6、10）。研究结果表明，自驱射流装置的置入确保了液体对表面的持续供给以及促进了气泡的脱离，从而有效增强了微多孔铜表面的临界热流密度（CHF）。然而，自驱射流的存在会对沸腾产生抑制作用，从而造成换热性能的轻微恶化，且抑制程度强弱与铜粉粒径尺寸大小呈正相关、与厚度与粒径之比大小呈负相关。参数化研究结果显示，沸腾换热性能随粒径增大而增大、随厚度与粒径之比增大先增大后降低。微多孔铜表面吸液能力均随铜粉粒径以及厚度与粒径之比的增加而提升，并且大部分情形下，搭配自驱射流装置与否，均不会影响其与CHF的线性正相关。但是，当粒径尺寸为101μm时，自驱射流装置会放大其过小的毛细力所带来的润湿劣势，进而造成CHF的偏低。与非微多孔铜表面的标准池沸腾性能相比，本研究的CHF和h_NB@CHF提升幅度分别可达189.2%和337.5%，最佳为CHF=72.0W/cm²和h_NB@CHF=87.5kW/(m²·K)。

关键词: 传热, 相变, 池沸腾, 介电液体, 烧结, 多孔介质