Simplified Procedure for the Determination of Thermal Resistance of Thick Specimens Enclosing Air Only

Procedures are presented in this paper for finding the thermal resis tance of thick products when the thermal resistance can not be measured directly because the specimen thickness exceeds the apparatus capabilities, typically 10-15 cm for guarded hot plate and heat flow meter apparatus, and when it can not simply be calculated as the sum of the thermal resistances of slices cut from the product because of the so-called thickness effect. The proposed method is applicable to air filled in sulating materials, i.e., only air in the cells or among the fibres. It consists of using interpolating equations, one measurement, and a set of material parameters that are known for the family products. For some insulating materials, diagrams are also sup plied which correlate the specimen transfer factor (called thermal conductivity) with specimen thickness and material thermal transmissivity (the measured thermal con ductivity at thicknesses such that the thickness effect may be neglected).