Energy and exergy model with parametric study of a hot water storage tank with PCM for domestic applications and experimental validation for multiple operational scenarios

摘要

Latent heat thermal energy storage (TES) with phase change materials (PCM) has been incorporated in domestic hot water (DHW) systems, frequently inside the water storage tank, as a way to improve its efficiency. The main challenge for further studies about optimization and design relies on finding accurate energy and exergy models capable of predicting diverse operating cycles with reduced computational resources. This paper describes the simulation and experimental validation of a PCM storage tank under multiple operational scenarios required in practice. Paraffin wax is used as PCM, contained in cylindrical bottles, to store and release energy during so-lid-liquid phase transformation. Simulation is addressed by using an integrated approach with both analytical and numerical methods, in which classic thermodynamic and heat transfer techniques are used to model the tank and the working fluid, and a finite difference formulation of the two-dimensional enthalpy method is im-plemented for the PCM. Experimental results were obtained by testing the system in laboratory conditions with different full 24-hour typical operating cycles, considering constant or variable inlet conditions during the thermal charging process along with constant flow rate discharge or batch-wise discharge. Predictions are in good agreement with experimental data. Lastly, the effects of key design parameters on the energy and exergy efficiencies of the PCM storage tank are also evaluated under different scenarios via parametric analysis of the model. Parameters considered in this study include the properties of PCM (mean melting temperature and latent heat of fusion), water flow rate, aspect ratio of the tank, and percentage of PCM inside the tank.