A Numerical Investigation Into the Flow Development and Heat Transfer Characteristics for Different Tube Geometry Configurations in a Water in Glass Evacuated Tube Solar Water Heater

Abstract

This study aims to numerically assess the heat transfer performance of water-in-glass evacuated tube solar water heater (WGET-SWH) for various parameters. It is observed that the natural circulation flowrate, velocity, and temperature distribution are strongly dependent on WGET-SWH geometry and operating conditions. The natural circulation flowrate is found to be increasing with tube length, diameter, inclination angle, and circumferential heat input. However, the heat transfer rate decreases with an increase in aspect ratio. The average Nusselt number increases with an increase in inclination angle till 45 deg and then decreases. Also, the study shows that thermal stratification in reservoir fluid is greatly influenced by circulation flowrate, flow momentum, collector outlet temperature, thermal acceleration, and buoyancy effect.