Simulation and Experimental Validation of solar water heater operating with selected Phase Change Materials

Abstract

Solar water heaters are widely known for their application in the domestic sector for heating water using free sunlight. However, the stochastic nature of sunlight especially in the tropical parts of the world, has created the need for some form of thermal energy storage to buffer the effect of the randomly varying solar insolation, and also to ensure a steady hot water delivery even during the night time, when the solar insolation is absent. This paper experimentally and numerically studies (using CFD software) the behavior of a solar water heater operating in the tropical climate of Nsukka, Nigeria, (Latitude 6.854^oN longitude 7.29^oE), incorporated with cetyl alcohol (Melting point: 47℃-50℃), palmitic acid (Melting point: 63℃-65℃) Myristic acid (Melting point: 50℃-53℃) and stearic acid (Melting point: 69℃-70℃)  as thermal energy stores. The experiments were carried out during the rainy season, with an average relative humidity of 83.26% and solar irradiance of 250W/m². The maximum average collector box temperature recorded was 55.62℃. The thermal performance of a solar water heater operating with cetyl alcohol, palmitic acid, myristic acid and stearic acid was measured, paying specific attention to their charging performance and hot water delivery during nighttime. A CFD model is also developed using ANSYS FLUENT and is used to simulate the collector box, hot water and PCM temperatures. The CFD model developed, predicted the PCM and hot water temperatures with a Root Means Square Error of 3.05℃ and 3.64℃ respectively, and with a Nash Sutcliffe accuracy of 98% and 99% respectively.

Keywords: Energy Storage, CFD, Solar Water Heater, Latent Heat, Collector, Solar Energy

DOI: 10.7176/JETP/10-5-05

Publication date:September 30^th 2020