Numerical modeling of walls with micro encapsulated PCM

Sammanfattning: There is a renewed interest to use material as wood to construct large multi-storey buildings in Sweden, but lightweight material tends to increase the indoor temperature fluctuations during days with large changes in outdoor temperature. The problem can be resolved by integrating phase change material (PCM) in the construction. This increases thermal inertia which mitigates the fluctuations.           The scope of the study is to develop a simulation model in COMSOL Multiphysics, to validate the model experimentally and to determine the optimal position and thickness of a PCM layer in a multi-layer wall. The model, representing a building with the shape of a box, consists of two versions. The first version, called the test box, is modeled with 5 sides of pure gypsum and 1 side of PCM-gypsum composite. The second version without PCM, called the reference box, is modeled with 6 sides of pure gypsum. Since the study is focused on reducing the cooling load, the PCM gypsum composite material should function effectively during summer conditions in northern Sweden. The experimental part includes two real-life boxes, the experimental test box and reference box, built of the same type of material that is chosen for the simulation model boxes. A climate chamber is utilized for the temperature control of the two boxes while performing measurements to validate the simulation model. The simulation model showed deviations from the experimental measurements. The temperatures inside the climate chamber, at all five points of measurement, were lower than the equivalent points in the simulation. It was possible to compensate by adjusting the overall ambient temperature down with 0.6 °C in the simulation, resulting in smaller errors. The PCM positioning resulted in recommendations to place the PCM closest to the interior space. The testing of different PCM thicknesses showed the best heat storage for the thickest PCM layers, but the PCM storage efficiency should have been considered as well.