Abstract: A heat storage water tank containing phase change materials (PCMs) for an air source heat pump system is studied with an aim to optimize the heating system for non-continuous sources of energy, such as solar heat, and air and geothermal heat etc. The water tank has a volume of 6 m³, containing 686 kg of paraffin with a phase change temperature of 46.78℃, encapsulated within 304 stainless steel tubes. A real scale model was established and investigated numerically using a Fluent software package. The effective enthalpy method was used to deal with the phase change process. It was found that the storage system can store 102.4 kW·h of heat within 9.2 h and continuously heat a low energy building for 11.1 h, meeting the heat demand of the building at night. This illustrated that an air source heat pump, coupled with the heat storage tank containing the PCM could achieve a large span of intermittent heating.

Key words: phase change energy storage, effective hot-melt method, heating system, numerical simulation