Modeling and numerical analysis of the phenomenon of reduction in thermal conductivity in small thickness samples of some selected synthetic materials

The phenomenon of reduction in thermal conductivity which is observed in thin samples (of some milimetres in thickness) of synthetic materials and the related temperature slip at the cold measurement surface of the sample have been studied. Various forms of depedence of the jump-like variation in essential thermal conductivity on the sample thickness have been simulated, their influence on the differential equation of steady-state heat transfer being studied for samples having the form of discs of different thickness. Our considerations were not concerned with particular synthetic materials, but the depedence of the essential thermal conductivity on the sample thickness and the temperature difference [delta]T = 65 degree C between the heater and the cooler of the plate apparatus assumed for the considerations were closely connected with earlier experimental investigations into the relations mentioned for polymethyl metacrylate and polyamide 6, pure and with soot addition [3, 7, 9]. It has been shown by numerical analysis that the phenomena of reduction in thermal conductivity of thin samples enables us to determine the depedence of the temperature slip on the plate thickness and explain the range and the character of that variation in the direction of sample thickness.