Enhancement of Solar Water Heater Performance Using Phase Change Materials

Abstract

ABSTRACT The solar water heater system (SWHS) is a well-known renewable energy technology that has gained a lot of global attention. The main drawback of such a system that it This work introduces an approach to the integration of Phase Change Materials (PCMs) within Evacuated Tube Solar Collectors (ETSC) for SWHS for domestic applications. The benefit of this technique is to enhance the thermal performance by delaying heat release, thus providing hot water when the intensity of the solar radiation is insufficient or during high-demand hours. Two models of ETSC namely: a heat pipe (HP) and a U-shaped tube were experimentally tested with and without PCM. The SWHS was tested experimentally during normal operation and at mass flow rate of 0.5,1and1.5 l/min.The simulation model was developed using CFD ANSYS Fluent R21 to analyze the melting and solidification process of PCM inside Utube ETSC. The experimental and numerical results showed that the time of the PCM melting process is directly proportional to the flow rate. The time of the solidification process is inversely proportional to the flow rate. The time delay for heat stored inside PCM integrated with HP -ETSC to HTF was approximately 2.16, 1.36 and 1.16 hours, for HTF flow rate of 0.5, 1and1.5 L/min respectively. The experimental abservations show that the enhancement efficiency of HP ETSC with integrating of PCM reach up to 28%, 22% and 16% as compared with simple HP-ETSC corresponds to flow rates of 0.5, 1 and 1.5 l/min respectively. The maximum increase in useful energy of HP ETSC was up to13%, 10% and 2% compared to simple configuration at flow rate of 0.5, 1 and 1.5 l/min respectively. Further the time period for heat release to HTF when using PCM with U-ETSC was approximately 77 ,60 and 31 min for HTF flow rate of 0.5,1,and 1.5 L/min respectively. However, enhancement in efficiency of U ETSC with integrating of PCM up to 26%, 20% and 12% at flow rates of 0.5, 1 and 1.5 l/min respectively. as compared to simple configuration of U-ETSC. The maximum rise in useful energy of U -ETSC with PCM can be reached up to 15%, 14% 10% at flow rate of 0.5, 1 and 1.5 l/min respectively. compared with simple U-ETSC system. As can be seen that HPETSC thermal performance is better than U-ETSC by providing a higher difference in HTF temperature between entry and exit and extended working time of SWHS during the night or cloudy days when integrated with PCM.