Factors Governing Heat Transfer through Closed Cell Foam Insulation

Abstract

The factors governing the heat transfer through foam insulation are reviewed and a predictive model is presented. Heat transfer takes place by conduction through gas within the foam cell, by conduction through the solid polymer and by thermal radiation. The gas conductivity is a function of the local gas composition. A given volume of polymer in a cell wall transmits twice the heat as the same volume in a strut. Radiation can be accurately predicted by assuming the cell walls are trans parent and the struts are opaque. The radiation heat transfer is proportional to the square root of the foam density and inversely proportional to the cell diameter to the first power. Addition of metal flakes to the polymer shows promise in reducing the transparency of the cell walls.

Keywords

foam heat transfer conductivity radiation

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