Publication

Abstract : The present work attempts to analyse the performance of a non-pressurised domestic solar water heater (DSWH) integrated with phase change material (PCM) during the two modes of operation, namely the charging and discharging modes. PCM's melting and the solidifying rate has been identified as the primary criterion influencing the heater's performance under standard test conditions. A co-axially placed cylindrical PCM container is modelled along with the evacuated tube collector (ETC) type water heater. A transient, three-dimensional numerical solver assuming constant solar insolation is used to study the phase change characteristics assisted by natural convective effects within the DSWH. The solver discretises the conservative equations using the finite volume method (FVM). Average solar insolation of 800 W/m2 has been fixed on the upper semi-cylindrical surface of ETC tubes and 35% of it as the reflected radiation falling on the ETC tubes' bottom surface. During charging, the melt fraction plot indicates that seven hours of charging is insufficient for the PCM to completely melt primarily due to the reduced heat conductivity of the PCM. Therefore, the extended period of discharge at the specified temperature expected by incorporating PCM is limited by the fraction of material remaining as solid.