乙醇水溶液单液滴碰撞热壁面的动态演化特性

doi:10.16085/j.issn.1000-6613.2020-0425

摘要/Abstract

摘要：

乙醇添加剂能显著改变去离子水基液滴碰壁动态特性。本文设计并搭建了液滴碰壁动态演化及传热研究实验台，并就溶液表面张力、液滴韦伯数（We）、壁面温度等对液滴碰壁的特性影响进行了实验研究。结果表明乙醇添加剂能够有效增强液滴润湿特性，促进液滴的雾化和破碎现象，同时抑制液滴反弹能力。并且这一能力随着乙醇溶液浓度的增大而增强。润湿特性随着液滴We的增大呈现出先增强后发生反弹现象的趋势，乙醇添加剂能够有效地抑制这种反弹趋势，并使混合液滴继续发生铺展现象。壁面温度125℃时，当We由15增大到33时，水基液由铺展阶段过渡到反弹阶段，而添加乙醇使得液滴继续铺展，没有发生反弹现象。乙醇添加剂能够明显地提高液滴由铺展到反弹的临界转变温度（T_CHF），扩大液滴核态沸腾对应的温度区域，延迟液滴进入过渡沸腾阶段。

关键词: 两相流, 传热, 相变, 对流, 液滴

Abstract:

Ethanol additive can significantly change the dynamic impact characteristics of deionized water. An experimental system was established to study the dynamic evolution and heat transfer of an ethanol-water droplet impacting on a heated surface. The effects of solution surface tension, Weber number (We) and wall temperature etc. on the characteristics of droplet impinging on the wall were studied. The results showed that ethanol additive could effectively enhance the wettability of the liquid droplets, promote atomization and fragmentation, and inhibit the rebound ability. Meanwhile, this ability increased with the concentration of ethanl solution. With the increase of droplet Weber number, the wettability was strengthened first and then rebound. Ethanol additive could effectively inhibit the rebounding and make the mixture droplets spread continuously. At wall surface temperature of 125℃, the deionized water changed from spreading stage to rebounding when Weber number increased from 15 to 33. However, the introduced ethanol could make the mixture droplets spread continuously without rebounding. Ethanol additive could significantly increase the critical transition temperature (T_CHF) from spreading to rebound, expand the temperature region corresponding to the nucleate boiling, and delay the droplet to enter the transition boiling stage.

Key words: two-phase flow, heat transfer, phase change, convection, droplet

中图分类号:

TK124

刘红, 司超, 赵传奇, 张博, 蔡畅, 尹洪超. 乙醇水溶液单液滴碰撞热壁面的动态演化特性[J]. 化工进展, 2021, 40(1): 74-81.

Hong LIU, Chao SI, Chuanqi ZHAO, Bo ZHANG, Chang CAI, Hongchao YIN. Dynamic evolution characteristics of an ethanol-water droplet on a heated surface[J]. Chemical Industry and Engineering Progress, 2021, 40(1): 74-81.

图/表 9

图1 液滴碰壁实验系统

表1 主要设备参数

设备名称	型号（规格）	实验参数
热电偶	GG-K-30	75~450℃
高速相机	FASTCAM Mini UX	4000fps
数据采集器	34972A	20fps
加液装置	OSASurfaceAnalyzer	8~12μL
加热棒	?6mm×40mm	500W
气凝胶	—	0.019W/m^-1·℃^-1

图2 液滴润湿直径和高度测量标准示意图

表2 去离子水及醇水混合溶液的物理性质（25℃）

乙醇体积分数/%	d₀/mm	σ/mN·m^-1	ρ/kg·m^-3	μ/mPa·s
0	2.44	72.8	996.7	1.0577
2	2.23	64.7	993.4	1.0603
4	2.21	59.5	990.2	1.0629
6	2.12	55.3	986.8	1.0656
8	2.09	50.2	983.5	1.0682

图3 不同浓度的乙醇-水溶液液滴碰壁动态演化过程

图4 不同浓度乙醇-水溶液的铺展因子（β）演化过程

图5 不同浓度乙醇-水溶液的铺展高度（H）演化过程

图6 乙醇-水溶液不同We下铺展因子（β）演化过程

图7 不同We、不同壁面温度下纯水和乙醇溶液液滴动态转变

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