Thermal performance and parameter analysis of a U-pipe evacuated solar tube collector

• We model thermal performance of U-pipe evacuated solar tube.
• Temperature distribution along fine circumferential direction is in consideration.
• Tube size parameters affects on thermal efficiency is studied.
• Mass flow rate optimal design is analyzed.
• Tube thermal parameters adaptation to metrological condition is proposed.

This paper proposes a mathematical model for predicting the thermal performance of U-pipe evacuated solar tube (UpEST) collector, which takes into account the temperature distribution along the tube axis and radius. Furthermore, the modeling predictions were validated using experimental data. Theoretical results agreed well with the measured results that validated the feasibility of the mathematical model. The dependence of the thermal efficiency on meteorological conditions and important tube design parameters, including tube size, thermal characteristics (flow rate, heat loss coefficient, absorption coefficient of the selective absorbing coating), was investigated. In particular, the adaptation of collector thermal parameters to meteorological conditions was analyzed. The analysis results will be helpful for UpEST collector optimization design and application.