Experimental validation of a simplified CFD model for a PCM-water finned heat exchanger

Abstract

The most widely used numerical models in the scientific literature for simulating heat exchangers with phase change materials (PCMs) and water as the heat transfer fluid, are based on computational fluid dynamics (CFD) techniques, with the modelling of phase change being the key issue. The consideration of phase change effect, as well as the resolution of the movement of the PCM in the liquid state, make CFD models computationally very expensive. However, various published experiments indicate that during the heat discharge process, the dominant heat transfer mechanism is conduction in the solidified PCM around the finned tube. For this reason, this article presents a simplified CFD model, where convective flow of the PCM is neglected during the discharge process. The model was validated experimentally, and to achieve this validation process, an experimental prototype of a one-meter-long axially finned heat exchanger with four fins was built. Inlet and outlet water temperatures were continuously recorded, along with temperatures at various points inside the PCM, under four different water flow rates. The proposed numerical model was able to predict the outlet water temperature with an error smaller than 1◦C in all cases, and to capture the observed trend in temperature inside the PCM.