Thermal analysis comparison of nano-additive PCM-based engine waste heat recovery thermal storage systems: an experimental study

The effect of energy and exergy analysis on the lauric acid and paraffin wax phase change materials (PCMs)-based 0.1% vol. fraction of Al2O3 and CuO nano-additives thermal energy storage (TES) system has been investigated experimentally. The TES system is integrated into the exhaust gas side of the four-stroke diesel engine. Nano-additives in phase change materials improve the charging rate of the TES system (i.e., a decrease in charging time). The temperature profile in radial and axial directions, heat transfer rate, overall heat transfer coefficient, heat transfer rate and the cumulative heat storage in the thermal energy storage system have been analyzed and were compared. Results revealed that 0.1% vol. fraction Al2O3 nano-additives-based lauric acid nano-enhanced phase change material (NEPCM) required 16.13%, 8.06%, 38.71%, 25.81%, and 32.26% less charging period than pure lauric acid PCM, CuO–lauric acid NEPCM, paraffin wax PCM, Al2O3–paraffin wax NEPCM, and CuO–paraffin wax NEPCM, respectively. However, the experimental analysis revealed an optimum thermal performance for the TES system with 0.1% vol. fraction Al2O3 nano-additive-based lauric acid PCM at 7kg engine load with 1500 rpm. Also, 0.1% vol. fraction Al2O3 nano-additives-based lauric acid (NEPCM) TES system along with the heat exchanger was highly effected to obtain the maximum percentages of the energy/exergy charging and energy/exergy saved from the diesel fuel compared to other considered samples.