The objective of this paper was to calculate effective thermal conductivity of polyurethane foam used in thermal insulation of buildings with a new modeling approach. The proposed approach was more realistic as it simulated the real fraction of closed cells and open cells in the foam and it modeled the real physical phenomena that happen when both types of cells are present. This study was investigated for polyurethane foam with 70 % of closed cells and 30 % of open cells, by using finite element method and numerical homogenization. The result showed that there was a systematic change in thermal conductivity when the type of cell (closed, open and mixed cell) varied at fixed volume fraction. Also the effective thermal conductivity of mixed cell of this PU foam was about λm= 0.07 W.m-1.K-1. Simulation proved the interest of this approach. Indeed, it brought new factor that influence the effective parameters which was fraction of closed cells and open cells. They suggested new method for computing thermal conductivity as a function of thermal conductivity of closed and open cell foam.
To design foams with specific properties, it is important to be able to predict their effective properties. The objective of this study is to compare and quantify the effect of the geometrical parameters on the thermal properties. Then the study uses both analytical and numerical homogenization methods to connect micro-scale parameters to the macro-scale thermal behavior. Several statistical studies of the morphology have been used to model the different categories of PU foams. The foam is modeled by a periodic structure of open, closed, or mixed cells. For each type of cell, different idealized shapes of a single cell are used, while keeping a constant porosity for each category. In the case of mixed
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