Effect of geometrical and operational parameters on paraffin's melting performance in helical coiled latent heat storage for solar application: A numerical study

In latent heat storage (LHS), the melting of phase change material depends on the flow path of the heat transfer fluid (HTF). The helical path is one of the most effective arrangements for the intended heat exchange between PCM and HTF. The geometric parameters of the helical path such as the coil diameter, coil pitch, tube diameter influences heat transfer rate. In the presented study, the geometric parameters of the helical path and HTF flow parameters are varied to study the effect on the PCM (paraffin wax 56 degrees C -58 degrees C) charging of the vertical helical coiled LHS system numerically. It is found that with an increase in the coil spacing, the charging process is improved, and approx. 20% of the melting time is saved if the 16 mm pitch is increased to 27 mm. The other parameters which affect the charging are the ratio of coil diameter to shell diameter, the optimal value of the ratio lies in the range of 0.65-0.75. In addition to the geometric parameters, different values of the operating parameters like inlet temperature and HTF flow rate are used to simulate the solar field application. When HTF's inlet temperature is increased from 70 degrees C to 75 degrees C and 75 degrees C to 80 degrees C, the required charging time is reduced by 28%, and by 22%, respectively. Moreover, when the HTF flow rate is varied from 1 LPM to 5 LPM, there is no significant difference in the charging rate of the PCM. The change in the geometric and operating parameters affects heat transfer and PCM motion thus melting rate varies.

Automated summary

This study investigates the effect of geometric and operating parameters on the charging of phase change material (PCM) in a vertical helical coiled latent heat storage (LHS) system. The results show that increasing the coil spacing and HTF inlet temperature can improve the charging process, while varying the HTF flow rate has no significant impact on the charging rate of the PCM.