Enhancement of phase change rate of PCM in cylindrical thermal energy storage

Abstract

Present study deals with melting and solidification of PCM inside cylindrical container with different shapes of shell and also different arrangements of inner tubes. Nine different cases with identical amount of PCM are considered for the investigation. The inner tubes are of constant temperature and the shell in all cases is adiabatic. Results show that conduction is the dominant mechanism at earlier time. Later, natural convection has significant effect on the melting process where PCM at the upper half of container is melted while a large amount of it is still solid at the lower half. Case with two tubes in vertical array and case with one tube have the highest and lowest melting rate, respectively. Longest and shortest solidification time respectively belongs to the case with two tubes located along x direction and case with four tubes in diamond array. Following to this, copper foam is inserted inside PCM to enhance the phase change rate which is solved by non-equilibrium thermal condition between metal foam and PCM. Results indicate that the temperature of metal foam ligament changes much faster than PCM. Moreover, inserting metal foam increases the melting and solidification rates up to 92% and 94%, respectively. However, it suppresses the natural convection especially in melting process.