Experimental investigation of the charging and discharging of latent heat in phase change material (PCM) based aluminium tube heat exchanger

Abstract

Abstract Nowadays, given the increasing importance of energy sources, the possibility of energy storage in the heat exchangers through the Phase Change Materials (PCM) and releasing it when needed has been extremely essential. This study seeks to develop a model as that of the domestic water heating system in which the phase change material is used for storing that heat energy as latent heat and it can be discharged during cooling. The behaviour of a PCM material is studied and the performance is tried to improve by using aluminium as the inner tubes instead of copper. In this experimental study, the thermal characteristics of PCM is studied by passing hot fluid and cold fluid through the tubes. Further the heat-storing capacity and the temperature distribution of wax along the tube was studied at different fluid temperatures. Also, the type of flow created by the fluid for different temperatures and the corresponding behaviour of the PCM during that particular temperature is also studied. A commercial grade Paraffin wax as PCM material with specific heat capacity of 2 kJ/kg-K is used and arrived at effectiveness around 0.48 for 40-50 °C and 0.59 for 50-60 °C. Logarithmic average of the temperature difference between 40°C-50 °C hot cycle is 10.654°C and during the cold cycle it is: 2.495°C, In the same way for 50°C -60 °C, during Hot cycle 11.56°C and for cold cycle 3.77°C. Finally, it is observed that based on the experimental study on the charging and discharging of latent heat storage, due to the low thermal conductivity of Phase change material, the rate of heat transfer during discharging is very low and the time required for discharging of latent heat storage is longer compared to the time required for charging of latent heat storage due to low heat transfer rate between PCM and hot Temperature fluid (Water).