Analysis of Operation Characteristics of Pulsating Heat Pipe Under the Condition of Non-uniform Heat Flux

doi:10.12141/j.issn.1000-565X.210548

Abstract

Abstract:

To further explore the influence of different operating parameters on the heat transfer characteristics of pulsating heat pipe under the condition of non-uniform heat flux and broaden the application scenarios of pulsating heat pipe, this study constructed an experimental platform of pulsating heat pipe with non-uniform heat flux. The platform consists of pulsating heat pipe module, heating module, cooling water circulation module, data measurement and acquisition module, and filling and vacuum working medium module. In order to ensure the reliability of the experimental results, the stability test was carried out. Under the conditions of 50% and 70% liquid filling rate, the performance of heat transfer, evaporation temperature and internal pressure fluctuation characteristics were studied by using ethanol and HFE-7100 as the working mediums and varying the heating power from 40W to 140 W and the dimensionless heat difference from 0 to 0.56. The results show that the HFE-7100 has lower operating thermal resistance at low heating power under uniform heat flux. With the increase of heating power, the thermal resistances of the two kinds of working fluid gradually get close to each other at 50% and 70% filling rate. Alone with the raise of dimensionless heat difference, the operating thermal resistance of the pulsating heat pipe under non-uniform heat flux is lower or close to the uniform heat flux. And the evaporation temperature of the pulsating heat pipe with high liquid filling rate has better stability during start-up and operation. There exists a critical value of dimensionless heat difference (0.33) for pulsating heat pipe under 70% liquid filling rate of non-uniform heat flux. When the value exceeds 0.33, the vapor-liquid working fluid at different heat flux sides can break the equilibrium rapidly, thus improving the circulating flow state and reducing the operating thermal resistance. When the ethanol working medium is heated with a uniform heat flux density, there are a large number of long liquid plugs in the tube under the high liquid filling rate, which is prone to the phenomenon of working medium flow stagnation. When the non-uniform heat flux density is heated, due to the high heat flux density side in the heating section of the device, the moving direction of the working fluid in the pipe of different elbows is consistent, reducing the stagnation and reversal in the internal fluid flow process, so as to improve the heat transfer performance of the pulsating heat pipe device within a certain dimensionless range.

Key words: pulsating heat pipe, heat transfer, dimensionless thermal difference, liquid filling rate, gas-liquid flow, gasification

CLC Number:

TK172.4

ZHANG Dong, HOU Hongyi, LI Qingliang, et al. Analysis of Operation Characteristics of Pulsating Heat Pipe Under the Condition of Non-uniform Heat Flux[J]. Journal of South China University of Technology(Natural Science Edition), 2022, 50(7): 126-135.

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物理量	测量方式	型号	测量范围	测量精度
温度	温度传感器	PT100	-50~650 ℃	B级
压力	压力传感器	UNF/7/16	-0.1~1.0 MPa	0.5%FS
加热功率	直流稳压电源	UTP1306S	0~32 V 0~6 A	≤0.1%+10 mV ≤0.2%+3 mA
流量	转子流量计	LZB-6	6~60 L/h	4级

工质	分子式	摩尔质量/ （g·mol^-1）		沸点/℃		密度/ （g·cm^-3）		比热/（J·kg^-1·℃^-1）
乙醇	C₂H₅OH	46.06		78.24		0.785		2 434.6
HFE-7100	C₄F₉OCH₃	250.00		61.00		1.510		1 183.0
工质	汽化潜热/ （kJ·kg^-1）		黏度/ （Pa·s）		表面张力（mN·m^-1）		（dp/dt）/ （Pa·℃^-1）
乙醇	920.66		1.081 7		21.97		601
HFE-7100	112.00		0.610 0		13.60		1 318

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