A 2D numerical analysis was conducted to examine the melting performance of a shell-and-tube-type phase change material with a two-layer copper foam having higher and lower porosity levels. The design parameters for these two layers of metal foam consisted of three different volume fill ratios (VFR) (30 %/70 %, 50 %/50 %, and 70 %/30 %) and three different shapes (circular, semi-circular, and elliptical) for the lower porosity layer. The results showed that a semicircular-shaped low porosity layer with a 30 % VFR had the least melting time of 475 s. When the VFR increased to 50 %, the elliptical and circular shapes had the least melting time of 394 s. However, at a VFR of 70 %, only the elliptical shape had the least melting time of 323 s. Furthermore, the results were compared with the uniform porosity metal foam system, and deduced that the two-layer system did not always have the lower melting time compared with that of the uniform porosity system because it depended on the VFR and shape of the different porosities filled in the different layers. Additionally, for an average porosity of the metal foam, an optimal combination of two different porosities was observed for the melting performance.
Numerous studies have been conducted to improve the heat transfer performance of PCMs. Studies [6,7] have shown that heat transfer can be improved by either expanding the storage system's heat transfer surface or raising the thermal conductivity of the storage material (i.e., PCM). Extended surfaces such as fins [8,9] and heat pipes [10] are frequently used to increase the heat transfer area. Highly conductive materials [11] and/or particles [12] are added to boost the thermal conductivity of PCM. Zhou and Zhao [13] investigated the heat transfer of a PCM embedded in open-cell metal foam and expanded graphite. They concluded that metal foam can provide a better heat transfer rate owing to its continuous structures. Junfei et al. [14] investigated the effect of the fin-metal foam structure on thermal energy storage. They concluded that in comparison to the bare tube, the melting time with the fins and metal foam was reduced by 52.8 % and 79.6 %, respectively. The metal foam was superior to the fins because it supported the uniformity of the temperature field inside the TES tube. Zhang et al. [15] conducted a comparative study on the heat transfer enhancement of shell-and-tube LTES systems with metal foam and fins. Their results showed that for a 3 % volume fraction of metal, the energy storage rate was approximately 20 times higher than that with the horizontal fins. Most of the recent studies favored metal foam as a suitable method for high heat transfer rates compared to the other methods. The different intensities of the uniform temperature distribution of the metal foam at different specifications prompted an in-depth study of the heat transfer phenomenon in PCM with metal foam.This study was supported by the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) [NRF-2022R1A4A3023960] and the Main Research Program (E0232100-01) of the Korea Food Research Institute (KFRI) funded by the Ministry of Science and ICT.This study was supported by the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) [NRF-2022R1A4A3023960] and the Main Research Program (E0232100-01) of the Korea Food Research Institute (KFRI) funded by the Ministry of Science and ICT.
