Transient modeling for the prediction of the temperature distribution with phase change material in a salt-gradient solar pond and comparison with experimental data

摘要

A Solar pond is a cost effective and environmentally friendly system, which can balance solar energy supply and demand particularly when is augmented with the phase change material (PCM). In this research, one-dimensional model for transient heat transfer using PCM has been proposed. The UCZ temperature was obtained using the convection, conduction, and radiation heat exchange with the ambient. In the LCZ, Paraffin Wax as PCM was used to seek its effect over longer time. The PCM media was modeled as a thin separated layer at the bottom of the pond. The energy balance was written for zones in the pond and the governing equations were solved numerically with and without the PCM. The proposed model was validated with the obtained experimental data. Maximum temperature errors between the numerical and experimental results of the LCZ for the pond without and with the PCM were 2.3 degrees C (4.5%) and 3.2 degrees C (6.2%), respectively. Numerical results show that in this setup significant amount of energy lost through the reflection, walls, convection, and evaporation. Only 6% of the available solar radiation was stored, which can be improved by good insulation. Further, this study presents criteria for the ratio of depth (vertical dimension) to radius (horizontal characteristic length) where the heat loss from the wall can be neglected. Finally, both numerical and experimental results indicated that using the PCM in the solar pond causes more steady stable temperature during the heat extraction.