This standard describes a method for the determination of the thermal resistance or the thermal conductivity.
In most materials the heat transfer is due to thermal convection through air or gas, thermal convection through the material which forms the product, as well as radiation.
This method, which is relatively fast, is based on calibration of the equipment by means of calibration discs, the thermal conductivity of which has been determined in a hot-plate apparatus, e.g. in accordance with ASTM C 177-76.
When measuring materials the assembly or construction of which may cause convection or radiation to the surroundings, the testing arrangements shall prevent such convection or radiation.
This standard describes two test procedures, both of which have been used with satisfactory results:
a) the heat-flow meter is placed between two test speci-mens (symmetrical arrangement — S), see figure 1.
b) the heat-flow meter is placed on one side of a single test specimen (asymmetrical arrangement — AS), see figure 2.
This standard applies to test specimens (two test specimens or a single test specimen) having a thermal resistance of at least 2 ·0,3 m2 ·°C/W for S and 0,3 m2 ·°C/W for AS, and a thickness of at least 2 · 30 mm and 30 mm, respec-tively.
Experience has shown that the results obtained by means of this method agree satisfactorily with those which are obtained with a guarded hot-plate apparatus for tempera-ture gradients ranging between 2.5 °C/cm and 10 °C/cm across the test specimen, subject to a minimum tempera-ture difference between the hot and cold surfaces of 15 °C.
The reproducibility of this method is considered to be better than 3 %.
DS 1120:1981 history
1981DS 1120:1981 Thermal insulation. Determination of thermal resistance or thermal conductivity by means of a heat-flow meter