THREE sets of apparatus have been described for the purpose of standardizing methods for testing the " comforting " value of textile fabrics. Heat insulation is measured in terms of thermal resistance, as expressed by the simple equation R J ~ T//I=~a, where R=thernlal resistance -(number of degrees centigrade temperature difference, between the specified surfaces of a specimen, required to produce a heat flow of I calorie per second through a test area of IOOO cm3) and J = 4.183, electrical equivalent of heat, /x7" = temperature drop through the test specimen, I -current flow in circuit of electrical resistance ~*. This test is made with the specimen exposed Oll the outside to conditioned air, as in use, and it is recommended that the temperature of the run (temperature of the hot plate) be 51.7 Β° C. (125 Β° F.).
It is pointed out that the problem, dealing with heat transfer through fabrics, is one of heat transmission rather than heat conduction. Fabrics are all relatively permeable to air and moisture and these properties may influence the passage of heat through a fabric, therefore, two other sets of apparatus are described for measuring the permeability to air and water vapor. The heat-transmission set is considered to be of primary importance and the other two tests to be auxiliary and of secondary importance. Comparison of this work with that of others shows the necessity for standardization of apparatus and methods of procedure in testing.
The heat-transmission apparatus is a duplex testing set. Either set consists essentially of two flat copper plates which are insulated from and inclose an electric-heating grid. The grid consists of a micanite core uniformly wound with constantan ribbon. Heat is supplied at a known rate to the inclosing copper plates of this test * Communicated by the Director. ' Technologic Papers, No. 266. Price. ten cents. 827