Influence of using nanofluid and phase change material on the performance of a solar thermal panel to provide the required energy of an office building in a mine

This paper examines the effect of using fins installed on tubes placed under a solar panel (SOP) numerically. The SOP is employed to generate electricity and hot water in a mine. The helical fins are mounted around the tubes under the SOP. By changing the cross-section of the fins, unsteady simulations are performed. Besides, OM37 phase change material (PCM) is utilized under the SOP and the tubes are placed inside the PCM. Alumina water nanofluid (NFD) flows inside the tubes, which are analyzed in two phases. The results show that for models M1 and M2 in 1500s, the use of tubes with a DIT of 5 mm under the SOP leads to a decrease in the SOP's average temperature of 8.58 and 8.24° respectively. The use of model M2 results in a lower outlet temperature (T-O) of the NFD when the tube DIT is 3 mm. Model M1 leads to a lower NFD T-O most of the time. Using the designed solar system can provide 56% of the hot water needed in the hot seasons and 18% of the hot water needed in the cold seasons for the building placed inside the mine.