电场对竖直矩形微槽群润湿及表面温度的影响

doi:10.16085/j.issn.1000-6613.2019-0597

摘要/Abstract

摘要：

微槽群在热流密度较大时会达到其毛细极限，可通过主动换热方式之一——电水动力学效应对其进行强化。本文为了研究电场对微槽群表面润湿特性和温度分布的影响，采用平板电极提供电场，蒸馏水作为工质，使用高速相机拍摄微槽内液体润湿长度，测量误差为2.97%～7.46%；使用红外热像仪拍摄电场作用下微槽群表面温度分布，测量误差为2.1%～2.39%。热流密度测量误差范围是9.66%～11.11%。结果表明：电场通过驱动微槽内流体向加热区域流动而提升其润湿性能，且较低热流密度下提升更好。因润湿性能的提升，微槽表面温度得以下降。随着电场增强，微槽横向温度分布的“波峰”、“波谷”差别加大，微槽纵向温度明显降低。当热流密度加大时，温降更为显著，1.4W/cm²热流密度、6kV电压下温降可达到30℃以上。温降的增加反映了电场对微槽的强化润湿进一步提升了微槽换热性能，且电场对较高热流情形下的微槽换热有着更为显著的强化效果。

关键词: 传热, 微通道, 矩形微槽群热沉, 电场, 温度, 红外热成像, 润湿性能

Abstract:

The capillary limit of the microgrooves is reached when the capillary pumping is not capable to overcome the pressure drops due to high heat flux. One of the active techniques, the electrohydrodynamic effect (EHD) can be used to deal with this situation and improve the thermal performance of microgrooves. To study the electric field effects on the microgroove wettability and temperature, a planar electrode pair was used to generate electric fields and the distilled water was used as working fluid. Using a high speed camera to record the wetting length, the measurement deviation is 2.97%~7.46%, and using an infrared thermal imager to record the temperature distribution, the deviation is 2.1%~2.39%. The heat loss deviation is 9.66%~11.11%. The results show that the electric field can enhance the microgrooves wettability by driving liquid towards the heated region. The enhancement is more distinguished when the heat flux is smaller. In addition, attributed to the enhanced wettability, the microgroove temperature is reduced. There exist “peak” and “valley” in the transverse temperature distribution, and the disparity between the “peak” and “valley” increases as the electric field increases. The longitudinal temperature decreases pronouncedly with the electric field increment. Higher heat flux leads to a larger temperature decline, which could reach 30℃ with 6kV under 1.4W/cm². The increased temperature decline indicates that the electric fields further improve the microgroove heat-transfer performance by enhancing the microgroove wettability, especially for higher heat flux conditions.

Key words: heat transfer, microchannels, microgrooves, electric field, temperature, infrared thermal imaging, wettability

中图分类号:

TQ021.3

于樱迎,唐瑾晨,胡学功. 电场对竖直矩形微槽群润湿及表面温度的影响[J]. 化工进展, 2020, 39(1): 26-33.

Yingying YU,Jinchen TANG,Xuegong HU. Electric field effects on wettability and temperature distribution ofopen rectangular microgrooves[J]. Chemical Industry and Engineering Progress, 2020, 39(1): 26-33.

图/表 11

表1 硼硅玻璃、PTFE板以及陶瓷加热片规格

部件	长度/mm	宽度/mm	厚度/mm
硼硅玻璃	90	20	1
PTFE保温板	80	50	7
陶瓷加热片	20	20	2

表2 润湿长度测量误差

误差原因	范围差距	误差值
游标卡尺误差Δ₁	0.03mm	0.04%～0.1%
人为操作误差Δ₂	0.1mm	0.13%～0.33%
干涸点定位误差Δ₃	2mm	2.66%～6.67%
液池液位下降误差Δ₄	1mm	1.33%～3.33%

图1 微槽群实验装置1—陶瓷加热片；2—直流电源；3—PTFE保温板；4—接地电极；5—高压电源；6—矩形微槽群热沉；7—高压电极

图2 6kV时液体内电场强度沿微槽轴向ξ的分布

图3 6 kV电压作用下微槽润湿长度随热流密度变化

图4 电场作用下热流密度对润湿长度的影响

图5 0kV、6 kV时微槽群表面温度分布

图6 不同电场作用下微槽表面温度沿y向分布

图7 不同电场作用下微槽表面温度沿x向分布

图8 微槽群热沉加热区域平均温度

图9 温度降与电场和热流密度的关系

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