ANNOUNCEMENTS
Energy plays an essential role in the growth of any country; since ancient civilisations, humankind has used energy for various purposes. Nowadays, a balance between energy supply and demand is a big concern for nations, mainly developing. Global warming and energy-related issues can be solved using renewable energy sources, energy-efficient technologies, and energy storage. The intermittent nature of renewable energy is one of the main drawbacks to utilising the energy source to its full potential. Energy storage technology can solve the mismatch between energy supply and demand, climate change and energy security.
The food processing, automotive and chemical industries are just a few sectors with a high demand for heat at low and medium temperatures for various processes. Thermal energy storage (TES) can play a crucial role in solar thermal applications, solar thermal power, biomass, district heating, heat pumps, combined heat and power, building applications, domestic and industrial heating applications, community kitchen applications, pharmaceutical industries, waste heat potential sector, iron and steel industries, chemical and petrochemical industries, paper and pulp industries, cement industries, glass industries.
Among the available TES technologies, latent heat storage (LHS) technology provides heat at constant temperature. The present works are based on developing a phase change material (PCM) based TES system consisting of material characterisation, simulation study and experimental prototype for validating the simulation model.
The thermal stability of PCM was analysed for 250 thermal accelerated cycles, and results show that enthalpy and melting temperature was decreased by 9.43% and 1.91% respectively. The corrosion tendency of the PCM was analysed on two different materials in two different experimental conditions. The corrosion rate for the stainless-steel sample for open and closed crucible was 0.23 mg/cm2.yr and 0.29 mg/cm2.yr, and mild steel samples open and closed crucible teste was 17.58 mg/cm2.yr and 31.14 mg/cm2.yr respectively for 2000 hr of immersion test with 3.14%, 2.38%, 0.03%, and 0.02% uncertainty. Hence, mild steel cannot be used for more extended periods of operation, whereas stainless steel can be used for more extended periods.
A simulation study shows that a nine-tube arrangement suits the selected capacity. The number of extended surfaces in each tube was also analysed, and results show that an increase in fins attached to each tube reduced the charging time by 25.55 % and 31.11 % for two-fin and four-fin configurations, respectively, from no fin condition for the nine-tube arrangement of the storage unit. HTF inlet temperature of 130 °C at 2.5 lpm took 90 minutes to charge the storage system; for the same inlet condition, 5.0 lpm took 87 minutes, whereas 7.5 lpm took 60 minutes to charge the storage unit. Similarly, charging time is significantly affected by HTF inlet temperature. The charging time is lowered by over 51.6% when the inlet temperature is raised by 10 °C from the initial testing condition of HTF, with the inlet temperature at 130 °C.
Several experimental studies were performed to examine the effect of varying inlet temperature. The temperature inside the LHS unit shows that the central portion of the storage unit melts first due to having a higher heating zone than others. Similar to simulation study, the charging time is more heavily impacted by the inlet temperature than by the flow rate. The simulation model shows good agreement with the experimental study. The average percentage error of temperature of the storage unit is ±5% of the model except for initial values for sensible heating of PCM in the solid phase.
