Experimentally validated axisymmetric simulation for thermo-fluid performance of an active flat-plate solar water heater at low flow rates

Abstract

ABSTRACT In this work, the thermo-fluid performance of a liquid flat-plate collector (FPC) has been analyzed using experimental and computational methods. A closed-loop active flat-plate solar water heater (AFPSWH) was tested under quasi-static and laminar flow operating conditions, where a maximum instantaneous collector efficiency of 62.82% and an outlet temperature of 45.2°C were attained in the winter with flow rates of 0.012 and 0.004 kg/s, respectively. Raising the flow rates from 0.004 kg/s to 0.008 and 0.012 kg/s reduces the energy loss parameter [FRUL] by 23.77% and 34.61%, whereas the absorbed energy parameter [FR(τα)n] improves by 10.48% and 21.55%, respectively. The suggested axisymmetric numerical model was validated with outcomes of an in-house developed lab scale experimental setup, with less than 1.5% deviations for all studied cases. In addition, the overall thermal efficiency of the solar thermal system (STS), Nusselt number (Nu), and friction factor (f) have been analyzed for a comprehensive understanding of the system’s thermo-fluid performance.