The thermal insulating properties of fabrics

One of the chief properties of a fabric is its thermal insulation, which prevents excessive heat-loss from the body. The paper gives a critical review of methods used in the past for measuring the thermal insulating properties. These are discussed with a view to the making of a new apparatus for the study of the subject. This apparatus consists of a copper cylinder with guard-ring ends heated electrically to skin temperature. With various fabrics the expenditure of electrical energy necessary to keep it at that temperature is measured. The surrounding conditions are defined by its being enclosed in a larger concentric tube whose temperature is regulated by the circulation of water round it. The humidity of the air can also be regulated. The temperature measurements are all by thermo-couple. The weight per unit area and the thickness of the fabrics are measured. There seems to be no definite relation between thermal insulating value and weight, but there is a relation which is very approximately linear between thermal insulating value and thickness. A detailed analysis of the results is being made.