High temperature phase-change material storage for thermal energy storage

• Main Author: Tan, Joon Kiat
• Other Authors: Fei Duan
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/75112
• Institution: Nanyang Technological University

Recovering waste heat from industrial activities has been an area of interest for the past few years. Phase Change Materials (PCMs) with their ability to store substantial amounts of heat energy in latent heat form are developing. In this study, to recover the thermal energy from heat source, a latent heat thermal energy storage system is designed with PCMs involved. A high temperature phase-change material, named as molten salt, is selected for energy storage. A differential scanning calorimetry (DSC) test is also carried out to verify the thermal properties of the PCM, and its melting temperature is measured around 220 ~ 230°C. A shell-tube type PCM tank is devised by 12 tubes arrays and a rectangular container, and each tube array is consisted of 12 cylindrical well-distributed tubes. Prior to the experiments, a transient, three-dimensional numerical model is first built on the basis of the enthalpy-porosity phase change method. To evaluate the performance of the PCM tank during the heat recovery process, the simulations on a single tube and a single tubes array are performed in order. In the simulation runs, different heat transfer mechanisms are also explored in the process. The comparisons of melting behaviour and heat transfer rate of PCM tank are presented when the natural convection is considered or not. By the fabrication of PCM tank in the stainless steel, the experiments are also conducted in the Energy System Lab. The heat source is supplied by several electrical heaters, and XCELTHERM 600 oil is used as heat transfer medium. The temperate profiles of entire melting process at different locations inside the PCMs are monitored, and the phase transition process can be clearly observed from the curves. The heat transfer rate of the PCM tank is also calculated. To investigate the effect of mass flow rate on the PCM melting process, three cases with different mass flow rates are tested. The experimental results showed no significant correlation between the mass flow rate and melting time of the PCM. Recommendations to further improve the overall setup are also discussed. One of the future works mentioned is further simulations, these can be conducted with a broader range of oil inlet temperatures and mass flow rates to make the prediction study more comprehensive.