Experimental study on the thermal performance of vertical closed-loop oscillating heat pipes and correlation modeling

Significance Statement

As a novel wickless heat pipe, oscillating heat pipes (OHPs) have received much attention in the last decade and considered as a viable alternative in modern highly efficient compact heat exchanger. The potential applications of oscillating heat pipes are involved in diverse areas, including but not limited to heat recovery, drying, solar energy collecting, cooling of electronics, LED and fuel cell. This contribution describes experimental studies on the effects of some important parameters (working fluid, heating power input, filling ratio by volume, inner diameter, and evaporator length) on the thermal performance of vertical closed-loop oscillating heat pipes. Then, with large number of available experimental data sets both from the present study and other literatures, an empirical power-law correlation, describing the flow and heat transfer characteristics, was developed to predict the thermal performance of vertical closed-loop oscillating heat pipes. The obtained reliable correlation is favorable to the design and application of oscillating heat pipes currently.

     

Figure Legend: figure shows the configuration of a closed-loop oscillating heat pipe.

 

Experimental study on the thermal performance of vertical closed-loop oscillating heat pipes and correlation modeling

Journal Reference

Applied Energy, Volume 112, December 2013, Pages 1154-1160.
Jian Qu, Qian Wang.

School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu Province, China

Abstract

Experimental studies were performed to investigate the thermal performance of three closed-loop oscillating heat pipes (CLOHPs) operating at the vertical bottom heat mode with heating power input in a range of 15–127 W. The tested CLOHPs are all made from copper capillary tubes with inner diameters (IDs) of 1.2, 2, and 2.4 mm. Two working fluids, pure water and ethanol, were used with filling ratios of 40%, 50%, and 60% by volume. The evaporator of each CLOHP was electrically heated with alterable lengths, while the condenser was liquid cooled with a constant length. Experimental results show that the thermal performance of the CLOHPs depends on the conjugation effects of working fluid, filling ratio, inner diameter, evaporator length, and heating power input. The 2 mm ID and 2.4 mm ID CLOHPs had better thermal performance when charged with water as compared with ethanol, while ethanol was preferred for the 1.2 mm ID CLOHP. The thermal performance of these CLOHPs was enhanced at the relatively lower filling ratios (40% and 50%). An optimum evaporator length corresponding to the lowest thermal resistance was proved. Finally, an empirical correlation based on 510 sets of available experimental data both from the present study and other literatures was proposed to predict the thermal performance of vertical CLOHPs. The proposed correlation agreed with the experimental data within a deviation of approximately ±40%.

 

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