Experimental study on enhancement of flow boiling through degassing with copper foam

doi:10.11949/0438-1157.20240109

Abstract

Abstract:

As an efficient heat exchange method, flow boiling is widely used in the cooling of high heat flow equipment. An independent porous hydrophobic structure designed in the flow boiling can promote the boiling bubble's departure and provide a new method to enhance the boiling heat transfer. Under various conditions including the inlet temperatures of liquid at 70, 75, and 80 ℃, flow velocity of 6.94, 10.42, and 13.89 cm/s, the flow pattern changes, the bubble suction process into copper foam and its effect on heat transfer performance were monitored. Based on the force analysis of boiling bubbles, the enhancement mechanism of superhydrophobic foam was obtained. As a result, the wall superheat decreases by 20.7% at high heat flux, and the heat flux is improved to 152% when the degassing rate of copper foam reaches 0.81 during experiments. The inlet flow velocity shows an obvious effect on the degassing process and heat transfer enhancement performance, while, the effect of inlet temperature can be ignored.

Key words: heat transfer, wettability, copper foam, gas-liquid flow, bubble

摘要：

流动沸腾作为一种高效的换热方法，被广泛应用于高热流设备的冷却。在流动沸腾换热过程中可通过设置多孔疏水结构促进沸腾气泡脱离，为强化沸腾换热提供新思路。在截面为6 mm×4 mm的矩形通道顶部添加浸润角为140°的多孔泡沫铜；并在液相入口温度70、75和80℃，流速为6.94、10.42和13.89 cm/s的不同工况下，观测通道内沸腾两相流流型变化以及泡沫铜的吸气过程对流动沸腾换热性能的影响；基于气泡受力分析获得泡沫铜吸气强化流动沸腾的换热机理。结果显示，在本实验工况范围内添加脱气泡沫铜后，壁面过热度下降可达20.7%；泡沫铜的吸气率为0.81时，热通量可提高至152%；增大入口流速，泡沫铜强化效果显著增大，而入口温度对泡沫铜的吸气效果影响不明显。

关键词: 传热, 浸润性, 泡沫铜, 气液两相流, 气泡

CLC Number:

TK 121

Chaoyang GUAN, Guoqing HUANG, Yinan ZHANG, Hongxia CHEN, Xiaoze DU. Experimental study on enhancement of flow boiling through degassing with copper foam[J]. CIESC Journal, 2024, 75(5): 1765-1776.

关朝阳, 黄国庆, 张一喃, 陈宏霞, 杜小泽. 泡沫铜导离气泡强化流动沸腾换热实验研究[J]. 化工学报, 2024, 75(5): 1765-1776.

Figures/Tables 14

Fig.1 Experimental system

Fig.2 Test section of flow boiling with the copper foam

Fig.3 Single-phase convective heat transfer

Fig.4 Model modification based on experimental results

Fig.5 Comparison of wall heat flux predicted by modified flow-boiling model with experimental data

Fig.6 Flow boiling heat flux enhancement

Fig.7 Boiling bubble merging at initiation

Fig.8 Degassing process of copper foam for various flow pattern in intense boiling

Fig.9 Variation of heat flux with different inlet temperatures

Fig.10 Variation of heat flux with different flow velocity

Fig.11 Degassing rate of copper foam and heat transfer enhancement performance under different conditions

Fig.12 Force analysis of a bubble growing on the heating wall of flow boiling

Fig.13 Bubble degassing by copper foam with liquid shear force in process of growing and sliding

Fig.14 Comparison of slip distance of a bubble slug with different flow velocity

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