Rotary Heat Recovery Wheel (RHRW) system with an embedded PCM: Proof of concept

Abstract

This work presents the thermal performance of a novel Rotary Heat Recovery Wheel (RHRW) system incorporating a Phase Change Material (PCM) embedded in the solid structure of the matrix of a rotating recuperator. The main aim of this device is to increase the thermal efficiency of the RHRW in two ways: by storing large amounts of thermal energy in latent form, and by permitting approach temperatures (around PCM melting point) that are closer to the desired setpoint temperatures for heating/cooling purposesA numerical model of the RHRW system with an embedded PCM was developed, comparing its performance against an identical RHRW without the PCM. The numerical model was validated with experimental data from the literature. A sensitivity analysis was carried out, varying the content of PCM embedded and the rotating speed of the wheel. Under the conditions tested in this work, for intermediate rotating speeds (between 0.1 and 0.7rpm) the PCM increases the efficiency of the system. For n=0.3rpm the efficiency augments from 0.44 to 0.87 with an addition of 15% in mass of PCM. There is also a certain rotating speed, nmax, for which the efficiency is maximum as the phase change of the PCM limits the temperature change. A relationship is proposed between the rotating speed and the mass fraction of PCM to reach the maximum efficiency.