Combined effect of nanofluid concentration and filling ratio on heat transfer performance of pulsating heat pipe

The installation and operation of enhanced geothermal systems (EGS) involves many challenges. These challenges include the high cost and high risk associated with the investment capital, potential large working-fluid leakage, corrosion of equipment, and subsiding land. A super-long heat pipe can be used for geothermal exploitation to avoid these problems. In this paper, a high aspect-ratio heat pipe (30 m long, 17 mm in inner diameter) is installed vertically. Experiments are then carried out to study its heat-transfer performance and characteristics using several filling ratios of deionized water, different heating powers, and various cooling-water flowrates. The results show that the optimal filling-ratio is about 40% of the volume of the vaporizing section of the heat pipe. Compared with a conventional short heat pipe, the extra-long heat pipe experiences significant thermal vibration. The oscillation frequency depends on the heating power and working-fluid filling ratio. With increasing cooling-water flow rate, the heat-transfer rate of the heat pipe increases before it reaches a plateau. In addition, we investigate the heat-transfer performance of the heat pipe for an extreme working-fluid filling ratio; the results indicate that the lower part of the heat pipe is filled with vapor, which reduces the heat-transfer to the top part. Based on the experimental data, guidelines for designing a heat pipe that can be really used for the exploitation of earth-deep geothermal energy are analyzed.

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Effects of filling ratio, geometry parameters and coolant temperature on the heat transfer performance of a wraparound heat pipe

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2021.117724 ◽

2021 ◽

pp. 117724

Author(s):

Cong Guo ◽

Tao Wang ◽

Chaohong Guo ◽

Yuyan Jiang ◽

Sicong Tan ◽

...

Keyword(s):

Heat Transfer ◽

Heat Pipe ◽

Heat Transfer Performance ◽

Filling Ratio ◽

Coolant Temperature ◽

Transfer Performance

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The Start-Up Performance of Pulsating Heat Pipe With Communicating Pipe at Different Inclination Angles

ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2019-4015 ◽

2019 ◽

Author(s):

Fu-Min Shang ◽

Shi-Long Fan ◽

Jian-Hong Liu

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Heat Pipe ◽

Heat Transfer Performance ◽

Working Fluid ◽

Transfer Performance ◽

Pulsating Heat Pipe ◽

High Heat Transfer ◽

Start Up ◽

Inclination Angles

Abstract The pulsating heat pipe (PHP) is a passive cooling device, which has the advantages of simple structure, high heat transfer performance and low production cost. The complex vapor-liquid phase change occurs in the in the initial stage of PHP. In this work, we explore the start-up performance of PHP at different inclination angles and the experiment shows that start-up performance is respectively different when the angles are 0°, 45°, 90°, 135° and 180°. Since the gravitational auxiliary function, the working fluid in the communicating pipe which takes longer time to vaporize change phase earlier than that in PHP’s loop when the angles are 0° and 45°. Nevertheless, when the angle is 90°, the phase change of working fluid in communicating pipe and in the loop occurs at the same time. Meanwhile, the oscillating mode affects the stability of the starting and heat transfer performance of the PHP.

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Heat Transfer Characteristics of Oscillating Heat Pipe With Water and Ethanol as Working Fluids

Journal of Heat Transfer ◽

10.1115/1.4002366 ◽

2010 ◽

Vol 132 (12) ◽

Cited By ~ 17

Author(s):

Haizhen Xian ◽

Yongping Yang ◽

Dengying Liu ◽

Xiaoze Du

Keyword(s):

Heat Transfer ◽

Heat Pipe ◽

Inclination Angle ◽

Heat Transfer Performance ◽

Filling Ratio ◽

Working Fluid ◽

Transfer Performance ◽

Heat Transfer Characteristics ◽

Oscillating Heat Pipe ◽

Transfer Characteristics

In this paper, experiments were conducted to achieve a better understanding of the oscillating heat pipe (OHP) operating behavior with water and ethanol as working fluid. The experimental results showed that there existed a necessary temperature difference between the evaporator and the condenser section to keep the heat pipe working. The maximum effective conductivity of the water OHP reached up to 259 kW/m K, while that of the ethanol OHP is of 111 kW/m K. Not all the OHPs are operated in the horizontal operation mode. The heat transfer performance of the ethanol OHP was obviously affected by the filling ratio and the inclination angle but the influence law is irregular. The effect of the filling ratio and the inclination angle of the water OHP were smaller than that of the ethanol one. The heat transfer performance of the OHP was improved with increase of operating temperature. The startup characteristics of the OHP depended on the establishment of the integral oscillating process, which was determined by the operating factors. The startup temperature of the ethanol OHP varied from 40°C to 50°C and that of the water, OHP varied from 40°C to 60°C without considering the horizontal operating mode. The water OHP showed a better performance and more stable heat transfer characteristics than the ethanol OHP, which had no obvious advantages of the startup capability as well.

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