Thermal and thermo-mechanical analysis of a novel pass-through all-glass evacuated collector tube by combining experiment with numerical simulation

• Published in: Energy (Oxford) 2023-08, Vol.277, p.127630, Article 127630
• Main Authors: Gong, Jing-hu, Zhang, Zhi-peng, Sun, Zhi-hao, Wang, Yu-guang, Wang, Jun, Lund, Peter D.
• Format: Article
• Language: English
• Subjects: convection; Dewar tube; energy; glass; mathematical models; Pass-through all-glass ETC; solar collectors; solar heaters; temperature; Thermal efficiency; Thermal expansion difference; Thermal stress; turbulent flow
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2023.127630

The collector tube could be a significant component of a solar water heater (SWH), that directly determines its performance and application eventualities. Here, a completely unique pass-through all-glass evacuated collector tube (ETC) is projected, which includes an easy structure composed inner and outer layers with each ends amalgamate along and no free ends. In addition, the flow pattern of the working medium in the tube also changes from laminar to turbulent flow, and natural convection changes to forced convection, greatly improving the convective heat transfer efficiency. Such a solar collector tube reaches 50% thermal efficiency at 54 °C in operation temperature and DNI = 1000W/m2, and might reach about 82 °C stagnation temperature at identical condition. Compared to standard Dewar tube, the pass-through ECT includes a higher thermal efficiency thanks to a lower inner layer temperature and better exit temperature. Completely different thermal expansions cause thermal stress within the glass structure, however the utmost stress between the inner and outer tubes was unbroken at intervals 40–120 MPa guaranteeing safe and stable operation at intervals the attainable temperature regime. The collector tube is a significant component of a solar water heater (SWH), which directly determines its performance and application scenarios. Here, a novel pass-through all-glass evacuated collector tube (ECT) is proposed as a solar collector. The ECT has a simple structure composed inner and outer layers with both ends fused together and no free ends. Such a solar collector tube reaches a 50% thermal efficiency at a 54 °C operating temperature and DNI = 1000W/m2, and can reach 82 °C stagnation temperature at the same condition. Compared to conventional Dewar tube, the pass-through ECT has a higher thermal efficiency due to a lower inner layer temperature and higher exit temperature. Different thermal expansions cause thermal stress in the glass structure, but the maximum stress between the inner and outer tubes was kept within 40–120 MPa ensuring safe and stable operation within the possible temperature regime. Fig. 1. Structure of straight-through all-glass evacuated tube. [Display omitted] •A novel pass-through all-glass evacuated collector tube is proposed as a solar collector.•Has a 50% thermal efficiency at a 54 °C operating temperature.•The maximum stress was kept within 40–120 MPa ensuring safe and stable operation.•Compared to conventional Dewar tube, it has