Composite metal foam/PCM energy store design for dwelling space air heating

Abstract

The objective of this numerical study is to develop a latent heat storage (LHS) air heater in both charging and discharging processes to find the geometrical and operating conditions for dwelling space heating. The aim of the storage heater is to provide a uniform output temperature according to the required heating load of a typical room in the required heating hours. The phase change material (PCM) is embedded in a copper porous structure to enhance the rate of heat transfer and overcome the low thermal conductivity of PCMs. The geometrical parameters is first obtained from analysing the discharging process including the height, air channel and PCM shell widths and air mass flow rate according to the discharging time as well as the output temperature of the air. Then, the charging mechanism is assessed to find the required area for the employed rectangular heating element. The results show the significant advantages of composite metal foam/PCM-air heat exchanger in comparison with the PCM-only unit on both the discharging time (56.5% reduction) and the uniformity of output temperature. The system with the height of 30 cm, PCM and air channel thickness of 15 cm and 2 cm, respectively, and a depth of 1 m, is capable to provide the desired output temperature of 47 °C for almost 17.4 h with the air mass flow rate of 0.01 kg/s. The charging analyses shows that the dimensions of the required rectangular heating element with constant temperature of 100 °C is 15 × 60 cm located at both sides of the unit.