(362f) Experimental Study on Thermal Performance of a Latent Heat Thermal Storage Cell Unit Utilizing Finned Metal Foam

The solar energy is an especial renewable energy with advantages of rich in sources, clean and pollution-free. Therefore, the solar energy has been regarded as an ideal candidate for substituting fossil energy to solve the increasingly serious environmental and energy issues. However, the inherent instability and intermittency of solar energy restricts the large-scale applications for practical engineering. In order to make up for the intrinsic deficiency in solar energy, the development of energy storage technology is a key to increase the share of solar energy in primary energy consumption.

It has been documented that the latent heat thermal storage (LHTS) is a better choose for energy storage in the field of concentrated solar power due to the advantages of the isothermal and reversible nature of the storage process, high energy storage density and small volume change. However, the intrinsic poor thermal conductivities of phase change materials (PCMs) restrict the rate of heat absorption and heat dissipation and hence reduce the thermal effectiveness of LHTS units in practical applications. To overcome this inherent problem, the addition of materials with high thermal conductivity, including metal foam, metal fins, graphite and fine metal particles, are widely utilized. Among these thermal conductivity enhancers (TCEs), metal foam has been verified as an attractive candidate due to its high specific surface area and high effective conductivity, which provides an integrated network for heat flow. In addition, inserting metal fins to extend the heat transfer surface are also a common method due to its simple techniques and low cost. However, the complexity and randomness of pore structures make understanding the phase change heat transfer of PCMs inside metal foam difficult. Furthermore, the research on the melting and solidification behaviors in LHTS units utilizing finned metal foam is few in the available literature. Therefore, it is of great significance to investigate the charging and discharging processes of finned metal foam (FMF) LHTS units, especially the role of pore structure in thermal performance.

To gain further insight into the charging process and hence to comprehensively evaluate the thermal performance of a FMF LHTS unit, a visualization experimental investigation of thermal performance of a FMF LHTS cell unit is conducted in this paper. The dynamic temperature and the melting front evolution of a FMF LHTS cell unit is analyzed by comparing the results of those of a corresponding finned LHTS cell unit. Additionally, the effects of porosity and pore density on the thermal performance of a FMF LHTS cell unit are examined and discussed. Furthermore, the enhancement ratio and thermal conductance of a FMF LHTS cell unit is evaluated for the optimization of the geometry of metal foam.