Multi-scale modelling of heat transfer in polyurethane foams

- Model for the prediction of heat insulation properties of PU foams is presented.
- Absorption spectrum of PU is computed by quantum chemical density functional theory.
- Thermal conductivity of PU, gas and gas mixtures is calculated by molecular dynamics.
- Equivalent conductivity of foam is determined by homogeneous phase approach.
- Validation by experimental data showed the successfulness of proposed model.

The influence of morphology and cell gas composition on heat insulation properties of polyurethane (PU) foams was investigated using a multi-scale mathematical model. The polymer absorption coefficient was determined from quantum chemical computations. Reverse non-equilibrium molecular dynamics was used to calculate the thermal conductivity of polymer and gas mixtures relevant to PU foams. The equivalent foam conductivity was calculated using homogeneous phase approach. The individual models were coupled together using suitable surrogate models within MoDeNa framework. To validate the proposed model 9 foam samples were prepared using different recipes, their morphology was characterized and their thermal conductivity was measured. The difference between experimental and predicted values was comparable to experimental error. Developed multi-scale model was used to identify the most suitable relation for the calculation of thermal conductivity of gas mixtures in PU foams and to quantify the influence of foam density, cell size, and strut content on heat insulation properties of PU foams.

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