Thermal energy storage (TES) based on hidden heat concept is good substitute for sensible heat storage because of its dense storage capacity and almost constant temperature heat transfers during the charging and discharging cycle. During no load and low cooling load conditions the system stores the thermal energy in the storage medium (phase change material) which will be used latter to meet the requirement in off cycle conditions. The intention of present work is to increase the system off cycle time, maintain required temperatures during power cuts by joining a few inch thick layer of phase change material on the outer surface of the evaporator. For investigation purpose a deep freezer which runs on vapor compression system of 50 liters storage capacity is fabricated with and without phase change materials. The eutectic compositions nearly 23 wt% salt (NaCl) dissolved in water and aluminium nitrate around 26 wt% dissolved in water are used as phase change materials. By the end of all experimental investigations it was noticed that the off cycle time system with phase change material is increased by 5.5 hours compared to system without phase change material, food storage time is enhanced by 8 to 14 hrs and a little power saving also achieved.
Optimization of an encapsulated phase change material thermal energy storage system
