Experimental charging and discharging performance of alumina enhanced pentaerythritol using a shell and tube TES system

The work presented in this paper is the results of an experimental study conducted on the thermal energy storage (TES) performance of pentaerythritol (PE) added with alumina (Al2O3) nanoparticles. The charging and discharging experiments are performed using PE added with 0.5 and 1.0 wt.% of Al2O3 in a shell and tube type thermal energy storage system. The experimental data are analyzed to obtain the charging/discharging efficiencies and the overall efficiency of the TES system at different flow rates 2, 4, 6 LPM of the heat transfer fluid (HTF, Therminol-55). Exergy analysis based on the 2nd law of thermodynamics is also carried out in this experimental work. The results indicated that charging and discharging time is reduced due to the addition of Al2O3 with PE at all volume flow rates of HTF. The maximum charging and discharging powers of 289.3 W and 230.8 W respectively are observed in the case of PE + 1.0% Al2O3 corresponding to the flow rate of 6 LPM. The efficiencies of charging and discharging showed maximum values of 86.8% and 75.0% respectively at 6 LPM. The overall energy efficiency of the thermal energy storage system found increased from 38.3% obtained in the case of PE to 50.5% and 58.5% obtained for PE added with 0.5 wt.% and 1.0 wt.% of Al2O3 nanoparticles respectively.