Effect of fill volume on solidification characteristics of DI (deionized) water in a spherical capsule – An experimental study

• Supercooling was eliminated with 95% fill volume at all surrounding bath temperature.
• The effect of higher fill volume is more pronounced with higher temperature potential.
• 50% mass is solidified in 10% of solidification duration with 95% fill volume at −12 °C.
• Several fold increase in heat flux is achieved with 95% fill volume at −12 °C.
• Combination of fill volume and temperature potential is essential for good design.

The present study aims to investigate the solidification characteristics of water, as the PCM (phase change material), due to the effect of fill volume of PCM in a spherical capsule. The experiments were conducted with the spherical capsule, filling it with water of 80, 85, 90, 92 and 95 percentage of its full volume and immersing it in a constant temperature bath maintained at various temperatures. It was observed that the increase in fill volume had a significant influence in reducing the degree of supercooling and it was eliminated with 95% fill volume. Further, the increase in fill volume had a considerable effect in advancing the commencement of solidification. Increasing the temperature potential enhanced the heat flux during the solidification of first 50% of PCM mass and its effect was more pronounced at higher fill volumes. The heat flux was increased several fold particularly at 95% fill volume making it highly suitable for applications that demand large cooling load in a short duration. Hence the proper selection of fill volume and temperature driving potential is essential to achieve overall energy efficiency while designing the CTES (cool thermal energy storage) system.