The effect of phase change material on the water temperature in a solar basin: Theoretical and experimental investigation

Abstract

• A model which significantly reduces the complexity of the numerical solution is introduced. • The system components can be assumed to have the same temperature. • Phase Change Material (PCM) produces two constant temperature zones. • Type of PCM determines the temperature in these zones. • Mass of the PCM/mass of water ratio and heat loss from the system greatly influence the length of the zones. In this work, a model to predict the variation of water temperature with time in a solar basin containing Phase Change Material (PCM) is developed. The model is based on the assumption that the temperature of the basin components (water, glass, PCM) varies within ±10% and hence represented by a single T value. The temperature versus time is divided into 5 zones: heating from ambient temperature till the melting point is reached (zone I), melting while T is constant at the melting point till complete melting occurs (zone II), heating reaching a maximum temperature nearly at noon time then cooling back to the melting point (zone III), solidification while T is constant at the melting point till the solidification process is completed (zone IV) and finally cooling back to the ambient temperature (zone V). The model described also the rate of melting and the rate of heating in the above mentioned 5 zones. The model is validated by comparing its results to those obtained by solving the energy equations governing its components numerically and second by comparing its results to those measured experimentally. An excellent agreement between the model and the experimental results as well as the numerical solution is found. The effect of the amount of PCM to the amount of water represented by the parameter R was examined. The results showed that as R increases the constant temperature zones become longer. Same results were obtained when the heat transfer coefficient was lowered.