Determination of heat transfer by radiation in textile fabrics by means of method with known emissivity of plates

High thermal resistance of thermal insulating fabrics is a major factor in the decision to use them in protective apparel applications, sleeping bags and other functional textiles. New standards and new applications of fibre layers in industrial textiles require more accurate methods of testing of their thermal resistance and conductivity, which minimise the dependence of the measured parameters on the testing conditions, such as the temperature drop between the plates of testing instrument and infrared radiation properties of these plates. In this article, the use of a testing method based on two different temperature drops between the plates of the ALAMBETA testing instrument revealed that the portion of heat transferred by radiation through the tested woven fabrics reached 12–17%. From the second series of measurements it follows that decrease in surface emissivity of the plates of the mentioned testing instrument influences the level of heat transfer by radiation between the plates of the ALAMBETA testing instrument and may cause the changes in the experimentally determined thermal conductivity and thermal resistance of certain porous fabrics. These changes presented up to 8% for the studied non-woven fabrics with low density.