CFD-based optimization of solar water heating systems: Integrating evacuated tube and flat plate collectors for enhanced efficiency

Abstract

The current research aims to explore the dynamic movement of fluid and heat involved in a hybrid solar water heating system using CFD. It introduces evacuated tube collectors, integrating these into solar flat plate collectors. This experiment aims to explore and understand how velocity, pressure, temperature, and streamline flows in turbulent kinetic energy are affected under varying fluid flow rates ranging from 1 lpm to 10 lpm. The results show that the lower flow rates, specifically 1 lpm and 4 lpm, promote better fluid flow in the collector array, thus leading to optimal convective heat transfer. Pressure distribution is found to be a predominant factor in influencing the heat transfer efficiency, as it increases linearly from inlet to outlet due to an increased flow rate. For example, although the pressure fluctuation ranges may differ by 39.3 % from inlet to outlet, the flow rate is at 1 lpm, temperature distribution varies with a different flow rate where the inlet temperature peaks at an efficiency of 68.5 % at a flow rate of 1 lpm. The investigation considered the turbulent effects induced by the water and utilized the usual k-ε turbulent model. Turbulent kinetic energy (TKE) also escalates with higher flow rates, ranging from 97.5 % at 1 lpm to 98.9 % at 10 lpm. To obtain convergence of the governing equations, the investigation was carried out under conditions that were considered to be quasi-static. A total of one thousand (1000) iterations were utilized. A high-resolution advection methodology was applied in the research, and first-order turbulence was added to the analysis. A residual of 0.0001 was established as the necessary condition for convergence for each and every one of the governing equations. The study emphasizes the significance of optimizing flow rates for enhanced efficiency and productivity in solar water heating systems.