Experimental investigation of wire-mesh equipped U-tube evacuated tube collector integrated with phase change material for hot water generation

Arun Uniyal, Yogesh K. Prajapati and Deepak Kumar

Applied Energy, 2025, vol. 377, issue PB, No S0306261924018841

Abstract: This paper presents an experimental investigation of the U-tube evacuated tube collectors (UETCs) integrated with phase change material (PCM). Three distinct experimental test sections were constructed, each comprising three tubes connected by a continuous U-tube configuration. The first setup, designated as Set-A, contained air within the evacuated space of the UETC. The second setup, SetB, involved filling the UETC's evacuated space with a PCM, whereas the third setup, referred as SetC, utilized a combination of wire mesh and PCM. Paraffin wax has been used as the PCM in Set-B and SetC. Liquid water is circulated as a heat transfer fluid (HTF) in all the cases. The comparative performance analysis of these setups was conducted over a span of three days, employing variable mass flow rates of 13 LPH (litres per hour), 7 LPH, and 10 LPH for Day-1, Day-2, and Day-3, respectively. The findings revealed that Set-A exhibited the highest HTF temperature until noon across all considered days. However, beyond this point, Set-C demonstrated superior performance, delivering hot water for extended durations of 108, 82, and 45 min at the respective flow rates of 7 LPH, 10 LPH, and 13 LPH. These durations represent an enhancement of 44.11 %, 41.55 %, and 70.88 % over those observed for Set-B on Days 1, 2, and 3, respectively. A significant observation was the variation in thermal stratification across the setups. Set-A displayed the highest degree of thermal stratification, followed by SetB, with Set-C exhibiting the lowest. Specifically, thermal stratification in Set-C was reduced by 83.41 %, 78.8 %, and 84.48 % relative to Set-A, and by 67.34 %, 78.90 %, and 79.55 % compared to Set-B for Days 1, 2, and 3, respectively. Furthermore, the investigation into daily thermal efficiency across the different setups revealed that Set-C achieved the highest thermal efficiency, followed by Set-A, and then SetB. This enhanced performance of Set-C underscores the effectiveness of integrating a wire mesh and PCM within the UETC, presenting a compelling case for the adoption of such configurations to improve solar collector efficiency.

Keywords: Solar energy; Water heater; Paraffin wax; U-tube evacuated tube collector; Latent heat (search for similar items in EconPapers)
Date: 2025
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DOI: 10.1016/j.apenergy.2024.124501

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