The Influence of Storage Tank Volume on the Nighttime Heat Dissipation and Freezing Process of All-Glass Vacuum Tube Solar Water Heaters

Shidong Wang, Xing Wang, Mingqiang Mao, Yongtao Wang, Shiping Liu, Baoming Luo and Tao Li ()
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Shidong Wang: Gansu Institute of Architectural Design and Research Co., Ltd., Lanzhou 730000, China
Xing Wang: School of Urban Construction, Wuhan University of Science and Technology, Wuhan 430065, China
Mingqiang Mao: Gansu Institute of Architectural Design and Research Co., Ltd., Lanzhou 730000, China
Yongtao Wang: Gansu Institute of Architectural Design and Research Co., Ltd., Lanzhou 730000, China
Shiping Liu: Gansu Institute of Architectural Design and Research Co., Ltd., Lanzhou 730000, China
Baoming Luo: Gansu Institute of Architectural Design and Research Co., Ltd., Lanzhou 730000, China
Tao Li: School of Urban Construction, Wuhan University of Science and Technology, Wuhan 430065, China

Energies, 2023, vol. 16, issue 12, 1-24

Abstract: The issue of freezing often occurs when using all-glass vacuum tube solar water heaters during cold winter seasons, leading to problems such as pipe ruptures and tank leakage. In order to further study the nocturnal heat dissipation and freezing characteristics of these heaters, a three-dimensional transient numerical model of their nocturnal heat dissipation was established. The model simulated the nocturnal heat dissipation process, and experimental validations were conducted through nocturnal temperature drops of the collector and temperature drops of individual tubes without a storage tank. Experimental and simulation results revealed that in clear weather conditions during cold winters in Luoyang, the all-glass vacuum tube solar water heaters experienced freezing issues during the night, with freezing predominantly starting from the bottom surface of the vacuum tubes. The frozen length along the tube wall and the thickness of ice at the bottom section reached up to 1180 mm and 5 mm, respectively. In the absence of a storage tank, the freezing situation was severe, with approximately 4/5 of the individual tubes completely frozen. Under specified operating conditions, different storage tank volumes exhibited varying degrees of freezing in the all-glass vacuum tube solar water heaters. When the volume was increased to 15 L, the temperature drop in the storage tank and the vacuum tubes decreased by 12.1% and 7.6%, respectively. Larger storage tank volumes resulted in reduced freezing risks in all-glass vacuum tube solar collectors. This study provides valuable guidance for the design and application of solar collectors and serves as a reference for the development and application of solar energy utilization technologies.

Keywords: freezing; all-glass vacuum tube; solar water heater; heat dissipation; transient numerical model; storage tank volume (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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