Open Access

ARTICLE

Experimental Analyses of Flow Pattern and Heat Transfer in a Horizontally Oriented Polymer Pulsating Heat Pipe with Merged Liquid Slugs

by Zhengyuan Pei¹, Yasushi Koito^2,*

1 Department of Mechanical and Mathematical Engineering, Graduate School of Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan
2Division of Industrial Fundamentals, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan

* Corresponding Author: Yasushi Koito. Email:

Frontiers in Heat and Mass Transfer 2024, 22(5), 1381-1397. https://doi.org/10.32604/fhmt.2024.056624

Received 26 July 2024; Accepted 08 October 2024; Issue published 30 October 2024

Abstract

Extended experiments were conducted on the oscillation characteristics of merged liquid slugs in a horizontally oriented polymer pulsating heat pipe (PHP). The PHP’s serpentine channel comprised 14 parallel channels with a width of 1.3 and a height of 1.1 . The evaporator and condenser sections were 25 and 50 long, respectively, and the adiabatic section in between was 75 mm long. Using a plastic 3D printer and semi-transparent filament made from acrylonitrile butadiene styrene, the serpentine channel was printed directly onto a thin polycarbonate sheet to form the PHP. The PHP was charged with hydrofluoroether-7100. In the experiments, the evaporator section was heated, and the condenser section was cooled using high-temperature and low-temperature thermostatic baths, respectively. Flow patterns of the working fluid were obtained with temperature distributions of the PHP. A mathematical model was developed to analyze the flow patterns. The merged liquid slugs were observed in every two channels, and their oscillation characteristics were found to be approximately the same in time and space. It was also found that the oscillations of the merged liquid slugs became slower, but the heat transfer rate of the PHP increased with a decrease in the filling ratio of the working fluid. This is because vapor condensation was enhanced in vapor plugs as the filling ratio decreased. However, the filling ratio had a lower limit, and the heat transfer rate was maximum when the filling ratio was 40.6% in the present experimental range.

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