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Thermal and hydrodynamic performance of an improved passive solar water heater equipped with asymmetric U-type evacuated tubes

Leilei Fan (College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China)
Zhilin Sun (College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China Ocean College, Zhejiang University, Zhoushan, China)
Wuyi Wan (College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China)
Yunze Shen (College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China)

International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Article publication date: 3 November 2022

Issue publication date: 20 January 2023

111

Abstract

Purpose

To modify a conventional evacuated tube, an improved asymmetric U-type evacuated tube (AUET) is proposed. This study aims to investigate the thermal and hydrodynamic performances of a modified tube and determine the optimal structural form.

Design/methodology/approach

Based on the variation of fluid proprieties with temperature, the formulated numerical model was validated and then deployed to investigate the natural circulation in the evacuated tubes. A dimensionless number was proposed to quantify the stratification effect. The influence of the degree of asymmetry of U-type evacuated tubes on the flow patterns, mass flow rate, temperature distribution, thermal stratification and energy conversion efficiency was studied.

Findings

When the degree of asymmetry is large, a higher velocity and better thermal stratification are achieved, thereby avoiding stagnant water at the bottom of the tubes simultaneously. Compared with the conventional evacuated tube, the improved evacuated tube exhibited a higher thermal efficiency.

Originality/value

The originally proposed AUET was proven to have better performance in avoiding stagnant water, reducing fluid mixing and improving the heat transfer efficiency.

Keywords

Acknowledgements

The authors would like to thank Kashif Mehmood for revising the language of the article. This research was supported by the Major Science and Technology Project of the Xinjiang Production and Construction Corps (No.2018AA003) and the National Natural Science Foundation of China (Grant Nos. 52079122, 51779216).

Data Availability Statement: The data and materials that support the findings of this research are available from the corresponding author upon reasonable request.

Conflicts of Interest: The authors declare no conflicts of interest.

Citation

Fan, L., Sun, Z., Wan, W. and Shen, Y. (2023), "Thermal and hydrodynamic performance of an improved passive solar water heater equipped with asymmetric U-type evacuated tubes", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 33 No. 3, pp. 1161-1183. https://doi.org/10.1108/HFF-03-2022-0195

Publisher

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Emerald Publishing Limited

Copyright © 2022, Emerald Publishing Limited

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