Experimental investigation on performance improvement of latent heat storage capsule by oscillating movement

Benefiting from the high availability of various phase-change materials (PCMs), latent heat storage is becoming one of the most important ways in the tune of energy production and demand. However, the charge and discharge power of latent energy stored in PCMs is impeded because of the low heat conductivity of the solid phase. Based on the principle that the relative motion of phase interface can enhance the heat transfer, this study presents a new way of enhancing heat transfer inside the PCM capsule by moving the capsule in an oscillating way. A crank and rocker reciprocating device was built to generate the vertical capsule oscillation, by which a stroke distance between 12 and 25 mm and an oscillation frequency between 1 and 3.7 Hz can be achieved. The capsule was made with hexadecane as the PCMs and brass as the shell. It is found that both the increase of the stroke distance and the increase of the frequency produce positive effects on the heat charge/discharge process. In the case of stroke distance of 25 mm and frequency of 3.7 Hz, the charge duration can be reduced from 36 mins to 26 mins and the discharge duration can be reduced from 153 mins to 127 mins. By analyzing the temperature variations inside the capsule, it is found that the melting and solidifying heat transfer coefficients could be improved maximally by 50% and 94%, respectively.