Travail de fin d'études et stage[BR]- Travail de fin d'études : Cooling Performance of Macro-Encapsulated Phase Change Material (PCM) Panels: Experimental Investigation and FEM Modelling[BR]- Stage d'insertion professionnelle : DTU

Abstract

This thesis aimed to investigate macro-encapsulated PCM panels (MEP) facing a high heat load. Another goal was to use Finite Element Method (FEM) to model MEPs and to analyse with precision more simple models as can be used in other simulation tools such as TRNSYS. The experimental investigation showed that ventilation parameters (inlet temperature and flowrate) and water circulation parameters (temperature setpoints for activation) determined the MEPs behaviour. This behaviour could be similar to TABS (when ventilation was dominant in terms of cooling during occupancy) or to a radiant ceiling (when the cooling impact of ventilation was reduced). By choosing the values of these parameters well, it was possible for the operative temperature to stay 95.8% of the time in Category II (including 92.1% of the time in Category I) according to EN 16798-1. It also showed that day-active water circulation could improve panel heat absorption by 35% with deactivated ventilation (reaching 21 W/m2 in average during occupancy). Three models were designed using FEM. One day of panel behaviour was simulated for each of them. A realistic model was validated using a criteria involving RMSEs on panel surface temperature and heat flux using measurements from the experimental campaign. A second model was designed using a simpler structure that could be implemented in other softwares. It could be validated using temperature measurements and values of heat flux computed from a theoretical formula. A comparison of these models regarding vertical stratification of PCM temperature showed that fins in the panel aluminum profile supporting the cooling water pipes enhanced thermal conductivity of the PCM layer. A third model was designed by using the same geometry as the Type399 TABS model of TRNSYS and by altering some PCM properties (density and thermal conductivity). This model could also be validated using temperature measurements and heat flux values from the same theoretical formula as the second model.