Role of PCM based nanofluids for energy efficient cool thermal storage system

• The high conductive carbon nanotubes acted as the nucleating agent.
• Use of nanofluid phase change material reduced subcooling considerably.
• Solidification time reduced by 20% with nanofluid phase change material at Tsurr = −12 °C.
• Use of nanofluid phase change material increases operating temperature of evaporator by 3 °C.
• An energy saving potential of 6%–9% is predicted in the chiller system.

This present study presents the solidification behavior of water based nanofluid phase change material encapsulated in a spherical container. The nanofluid phase change material (NFPCM) was prepared by dispersing the multi wall carbon nanotubes (MWCNT) with volume fractions of 0.15%, 0.3%, 0.45%, and 0.6% in de-ionized (DI) water as the base phase change material. The solidification experiments were conducted with DI water and the NFPCM and maximum reductions of 14% and 20.1% were observed in the solidification time with the NFPCMs at surrounding bath temperature of −9 °C and −12 °C respectively. The presence of MWCNT also acted as nucleating agent that caused appreciable reduction in the subcooling. The enhanced thermal transport properties of the NFPCM are very useful to operate the cool thermal energy storage (CTES) system at higher operating temperature of the secondary refrigerant. It is predicted that there is a possible energy saving potential of approximately 6–9% in the CTES using the NFPCMs.