Visualization experiment of two-phase flow in parallel flow heat pipe

doi:10.11949/0438-1157.20201269

Abstract

Abstract:

The parallel flow heat pipe heat exchanger integrates the advantages of high efficiency heat exchange in the axial direction of the heat pipe and high efficiency heat exchange outside the parallel flow heat exchanger, and is a new type of heat pipe heat exchanger. In order to study the working mechanism and the flow process of the parallel flow heat pipe, a visualization experimental rig was set up, and the startup characteristic and the heat and mass transfer law of parallel flow heat pipe under different structural parameters, different heating powers and different working mediums were experimentally studied combined with high speed camera technology and infrared-ray test technology. The results show that the working mechanism of the parallel flow heat pipe is complicated. The gas column and the liquid column in the tube carry out the mutual oscillating flow due to the gravity and unbalanced pressure in the parallel multiple pipelines. Moreover, the flow patterns in the branch pipe are varied, including bubble flow, slug flow, annular flow and the like. At the same time, it is found that larger diameter and higher heating power will aggravate the oscillating flow between parallel pipelines, increase the disturbance of the working medium in the evaporation section and the condensation section, and enhance heat transfer performance of heat pipe.

Key words: parallel flow heat pipe, two-phase flow, visualization, flow, heat transfer

摘要：

平行流热管换热器综合热管轴向高效换热和平行流换热器管外高效换热的优点，是一种新型的热管换热器。为了研究平行流热管工作机理及管内流动过程，搭建了平行流热管可视化实验台并对不同结构参数、不同加热功率和不同充注工质下的启动特性和传热传质规律进行了实验研究。实验结果表明：平行流热管工作机理复杂，并联管路内气柱和液柱在重力和不平衡压力的共同作用下进行互激振荡流动，并且管内出现泡状流、弹状流、环状流等多种流型，同时较高的加热功率和较大的管径会加剧工质在并联各管路之间的往复振荡，增加工质在蒸发段和冷凝段的扰动，提高热管的换热性能。

关键词: 平行流热管, 两相流, 可视化, 流动, 传热

CLC Number:

TK 172.4

SHEN Chao, LIU Yujuan, WANG Zhuxuan, ZHANG Dongwei, YANG Jianzhong, WEI Xinli. Visualization experiment of two-phase flow in parallel flow heat pipe[J]. CIESC Journal, 2021, 72(5): 2506-2513.

沈超, 刘玉娟, 王竹萱, 张东伟, 杨建中, 魏新利. 平行流热管管内两相流动可视化实验研究[J]. 化工学报, 2021, 72(5): 2506-2513.

Figures/Tables 13

Fig.1 Structural diagram of parallel flow heat pipe

Table 1 Sample parameters of parallel flow heat pipe

实验样品	平行流热管参数
实验样品	管长/mm	管径/mm	集液管和均压管管径/mm	工质	管间距/mm	充液率
1	300	4	8	丙酮	4	0.258
2	300	2	6	丙酮	6	0.26
3	300	4	8	甲醇	4	0.258

Table 2 Thermophysical parameters of different working fluids at standard atmospheric pressure

工质

沸点T_s/℃

密度ρ_l（20℃）/

(kg/m³)

比热容C_pl（20℃）/

(kJ/(kg·℃))

热导率λ_l（20℃）/

(W/(m·℃))

汽化潜热H_fg（20℃）/

(kJ/kg)

(dP/dT)_sat（60℃）/

(kPa/℃)

动力黏度υ_l（20℃）/

(mPa·s)

Fig.2 Schematic diagram of the parallel flow heat pipe visualization experimental rig

Fig.3 Working fluid flow and surface temperature distribution of parallel flow heat pipe evaporation section (4 mm, acetone, 10 W)

Fig.4 Working process of parallel flow heat pipe (4 mm, acetone, 30 W)

Fig.5 Temperature distribution before and after startup of parallel flow heat pipe (4 mm, acetone, 30 W)

Fig.6 Working process of parallel flow heat pipe (4 mm, acetone, 50 W)

Fig.7 Temperature distribution before and after startup of parallel flow heat pipe (4 mm, acetone, 50 W)

Fig.8 Working process of parallel flow heat pipe (2 mm, acetone, 50 W)

Fig.9 Surface temperature distribution of parallel flow heat pipe after startup under different pipe diameters (acetone, 50 W)

Fig.10 Working process of parallel flow heat pipe (4 mm, methanol, 50 W)

Fig.11 Temperature distribution of parallel flow heat pipe after startup under different working fluids（4 mm，50 W）

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