International Journal of Refrigeration 100 (2019) 454–462 Contents lists available at ScienceDirect International Journal of Refrigeration journal homepage: www.elsevier.com/locate/ijrefrig Experimental studies on solidification and subcooling characteristics of water-based phase change material (PCM) in a spherical encapsulation for cool thermal energy storage applications M. Ponrajan Vikram, V. Kumaresan ∗ , S. Christopher, R. Velraj Department of Mechanical Engineering, CEG Campus, Anna University, Chennai 600025, Tamilnadu, India a r t i c l e i n f o Article history: Received 12 June 2018 Revised 5 November 2018 Accepted 20 November 2018 Available online 1 December 2018 Keywords: Phase change materials Cool thermal energy storage Cooling rate Solidification Subcooling a b s t r a c t This work aims to investigate the solidification behavior of de-ionized (DI) water as the base phase change material (PCM) dispersed with various mass fractions of sodium chloride and D-sorbitol in a spherical encapsulation. The DSC analysis of water illustrated that subcooling of DI water increases with respect to cooling rate due to inadequate time to complete the crystallization. The solidification experi- ments were carried out at a bath temperature of −7 °C and DI water undergoes a subcooling of −5.4 °C. However, the subcooling substantially reduced to −2.8 °C for DI water with 0.5 wt. % sodium chloride and 1 wt. % of D-sorbitol. Accelerated mode of charging prevails in all the PCM samples and the innermost 6% of volume got solidified in decelerated mode. The cooling rate is found to decrease with respect to increase in concentration of the dispersants in subcooling region, but at a particular concentration both dispersants provide the enhanced cooling rate for a given driving potential than DI water. It is concluded that reduction of subcooling and partial charging of water based PCMs would be helpful to enhance the energy efficiency of the cool thermal energy storage (CTES) system. © 2018 Elsevier Ltd and IIR. All rights reserved. Études expérimentales sur les caractéristiques de solidification et de sous-refroidissement d’un matériau à changement de phase (PCM) à base d’eau dans une encapsulation sphérique pour des applications de stockage d’énergie thermique froide Mots-clés: Matériaux à changement de phase; Stockage d’énergie thermique froide; Vitesse de refroidissement; Solidification; Sous-refroidissement 1. Introduction Thermal Energy Storage (TES) system is one, which stores the cool or hot thermal energy in the off-peak hours and retrieves it to meet out the spasmodic energy demand during the peak hours. Due to the wide spread applications of the TES system in differ- ent energy intensive sectors, its global thermal energy market is estimated to be 8862 million US dollars during 2017–22 (Doshi, 2017). Moreover, the recent rapid urbanization and industrializa- tion result with enormous increase in energy consumption, partic- ularly in the developing country like India, at the increasing rate ∗ Corresponding author. E-mail address: kumaresanvm1973@gmail.com (V. Kumaresan). of 7% per year. The above data necessitate the development of an energy- efficient TES system for various applications such as food preservation, transportation, electronic cooling and heating / cool- ing for buildings (Oró et al., 2012; Zalba et al., 2003). The cool ther- mal energy storage (CTES) system is one of the most appropriate methods for thermal management of buildings and it gains mo- mentum nowadays, in terms of both energy conservation and envi- ronmental impacts. In addition to that, the integration of CTES sys- tem with the chiller unit appreciably reduces the electricity cost, by shifting the off-peak time during a day, where the cooling re- quirement is highly intermittent. The stored cool thermal energy is in the form of sensible or latent heat and the low energy den- sity and variable discharging temperature of sensible thermal en- ergy storage (SHTES) systems obviously make them less efficient https://doi.org/10.1016/j.ijrefrig.2018.11.025 0140-7007/© 2018 Elsevier Ltd and IIR. All rights reserved.