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

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 6.854oN longitude 7.29oE), 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 30th 202

Performance Evaluation of Native-Kankan Padded Evaporative Space Cooler Using Arduino Mega

Performance evaluation of native-kankan padded evaporative space cooler using Arduino Mega is presented. Materials for fabrication were both locally improvised and conventionally sourced for such as the Nigerian Native-Kankan fibre sponge used as the wet and dry filter pads and expanded polystyrene which is used as thermal insulation material. Dry air from the outdoor surrounding is passed through the soaked Kankan fibre pad using a reverse DC fan and cooled by evaporative means where the sensible heat of dry air is converted to latent heat accumulation in the circulating working fluid. 150Watts solar power was supplied to the constructed cooler for a test run and results showed that the peak temperature drop of 27℃ to 24.5℃ was experienced in the indoor space / cooler exit of the test room facility. The average system COP of 1.224, evaporation rate of 0.066GPH and cooling capacity of 95.23W was achieved from the conducted experiment. The native-kankan dry filter pad reduced the humidity level of cooled air entering the indoor test room cubicle by 2%. A comprehensive cooling load analysis of the test room facility was carried out and the results were applied using sensible heat removal method to achieve cooler size rating of 319.02CFM. All experimental results were collected using Arduino Mega, type K thermocouple sensors and DHT11 humidity sensors installed on the constructed evaporative cooling unit. Keywords: Latent heat; Air conditioning; Relative Humidity, Arduino Mega; Evaporative Cooling; Native-Kankan fibre sponge