Phase change material nanocomposites for thermal energy storage applications on solar water heater
Hussain Saad, Ameer Abed Jaddoa, Hadia Kadhim Judran, Jafaar Mohammed Daif Alkhasraji, Safa J. Aqool, Miqdam T. Chaichan
Abstract
The thermal capacity of a fully glass-based transparent tube solar water heater can be improved using a phase change material (PCM) and a PCM nanocomposite. Paraffin was used as the phase change material in the tests, and selected nanoparticles of Al 2 O 3 and TiO 2 were added at 0.5 % mass to the paraffin. The aim of the study was to conserve as much of the received solar energy as possible to be used for heating water after sunset. The experimental results were validated under real conditions on a solar water heater consisting of a water tank with thermal energy storage inside and sixteen evacuated glass tubes. This system uses thermosiphon flow. The tests were conducted without adding a thermal storage material, with paraffin and nano-paraffin added to the water tank. The temperature of the tank water was measured from 7:00 a.m. to 7:00 p.m. During this period, the energy efficiency and thermal energy of all the studied cases were evaluated. Experiments showed that after a full working day, at 7 p.m., the water temperatures in the water-water-paraffin, water-paraffin-nano Al 2 O 3 , water-paraffin-nano TiO 2 systems were 36 °C, 49 °C, 55 °C, and 52 °C. The energy efficiencies in the three studied scenarios were 37.7 %, 41.4 %, and 45.8 %, respectively. The exergy efficiencies of these systems were 2.67 %, 3.85 %, and 4.65 %, respectively. The addition of Al 2 O 3 and TiO 2 nanoparticles increased the thermal conductivity (TC) of the resulting mixture by 61.05 % and 44.7 %, respectively. In conclusion, the use of PCM and the addition of Al 2 O 3 and TiO 2 nanoparticles made the system more thermally efficient.