Experimental study on the melting and solidification behaviour of a medium temperature phase change storage material (Erythritol) system augmented with fins to power a LiBr/H2O absorption cooling system

Experimental studies using a concentric annulus storage system with Erythritol (melting point of 117.7 °C) as a phase change material (PCM) and augmented with longitudinal fins on the shell side, have been conducted to assess the thermal behaviour and heat transfer characteristics of this system. The study forms part of a broader investigation of PCMs to store energy to operate a LiBr/H2O absorption cooling system which operates with generator inlet temperatures of 70 °C–90 °C. The experiments investigated the effect of changing mass flow rates (m˙) and inlet heat transfer fluid (HTF) temperatures (Tin) on the thermal behaviour of the PCM system. The results showed that the suitable mass flow rate and inlet HTF temperature for charging the system to power a LiBr/H2O absorption system are m˙=30kg/min and Tin = 140 °C respectively. The experimental programme also investigated the temperature gradient in the axial, radial and angular directions during charging to help predict heat transfer in the system during phase change of Erythritol. Isothermal plots and temperature–time curves were used to analyse the results. Temperature gradients in the axial and angular directions were 3.6% and 9.7% respectively that of the radial direction, indicating essentially a two-dimensional heat transfer in the radial and angular directions during the phase change. The amount of energy recovered from the 20 kg store during solidification was 70.9% of the maximum energy charged, at an average temperature of 80 °C.