Determination of critical pressure in the free molecular region and performance analysis of vacuum glass-covered flat plate collector under typical days

• Published in: Journal of physics. Conference series Vol. 2840; no. 1; pp. 12033 - 12039
• Main Authors: Li, Yan, Wu, Shuang-ying, Xiao, Lan
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.09.2024
• Subjects: Critical pressure; Equinoxes; External pressure; Flat plates; Heat loss; High vacuum; Interlayers; Meteorological parameters; Performance evaluation; Rarefied gases; Solstices; Summer solstice
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/2840/1/012033

The pressure of the gas in the interlayer of the vacuum glass-covered flat plate collector (VGFC) is critical in evaluating its performance. Even though the gas in the interlayer under high vacuum conditions is in the free molecular region, the critical pressure is also influenced by external environmental parameters. In this paper, based on the theory of heat transfer of rarefied gas in the free molecular region and the principle of energy balance, a mathematical-physical model of VGFC was established and validated under two typical days’ meteorological parameters of the spring equinox and the summer solstice. The results show that, compared with the spring equinox day, on the summer solstice day, the critical pressure of the interlayer gas under the free molecular region is notably higher and exhibits greater fluctuations. Specifically, the minimum and maximum critical pressures of the gas increased by 7.88% and 16.2%, respectively. Additionally, the heat loss coefficient of the top of the VGFC is also significantly higher than on the spring equinox day, with an increase of 6.58%.