An investigation into the use of the heat pipe technology in thermal energy storage heat exchangers

Finding a solution to store industrial wasted heat for later use in order to reduce energy usage has been on the rise in recent years. This paper investigates the capability of latent heat TES (Thermal Energy Storage) system using PCM (Phase Change Material) to store/release a large amount of energy in a small volume compared to sensible heat TES system. In this work, the issue of the low conductivity of PCMs has been addressed by using an embedded finned water-charged heat pipes into the PCM bulk. Both heat pipes and the PCM tank used in this investigation were made of 316 L stainless steel. The PCM used in this work was PLUSICE S89, which has a melting temperature of 89 °C and crystallization point of 77 °C. The evaporator section of the heat pipe was heated by condensing a steam flow. The heat that was absorbed in the evaporator section was then discharged to the PCMs by the heat pipe multi-legged finned condenser. Tests were conducted for both charging (melting) and discharging (crystallization) of PLUSICE S89. It was observed that the thermal resistance posed by PCM during the discharging stage was higher compared to that during the charging process.