BS EN ISO 11092:2014 pdf free download.Textiles – Physiological effects Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded-hotplate test) (ISO 1 1092:2014).
BS EN ISO 11092 specifies methods for the measurement of the thermal resistance and water-vapour resistance, under steady-state conditions, of e.g. fabrics, films, coatings, foams and leather, including multilayer assemblies, for use in clothing, quilts, sleeping bags, upholstery and similar textile or textile-like products.
The application of this measurement technique is restricted to a maximum thermal resistance and water-vapour resistance which depend on the dimensions and construction of the apparatus used (e.g. 2 m2•K/W and 700 m2•Pa/W respectively, for the minimum specifications of the equipment referred to in this International Standard).
The test conditions used in this International Standard are not intended to represent specific comfort situations, and performance specifications in relation to physiological comfort are not stated.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1 thermal resistance R1 temperature difference between the two faces of a material divided by the resultant heat flux per unit
area in the direction of the gradient
Note I to entry: It is a quantity specific to textile materials or composites which determines the dry heat flux across a given area in response to a steady applied temperature gradient. The dry heat flux may consist of one or more conductive, convective and radiant components.
Note 2 to entry: Thermal resistance is expressed in square metres kelvin per watt.
2.2 water-vapour resistance
water-vapour pressure difference between the two faces of a material divided by the resultant evaporative heat flux per unit area in the direction of the gradient
4 Principle
The specimen to be tested is placed on an electrically heated plate with conditioned air ducted to flow across and parallel to its upper surface as specified in this International Standard.
For the determination of thermal resistance, the heat flux through the test specimen is measured after steady-state conditions have been reached.
The technique described in this International Standard enables the thermal resistance of a material to be determined by subtracting the thermal resistance of the boundary air layer above the surface of the test apparatus from that of a test specimen plus boundary air layer, both measured under the same conditions.
For the determination of water-vapour resistance, an electrically heated porous plate is covered by a water-vapour permeable but liquid-water impermeable membrane. Water fed to the heated plate evaporates and passes through the membrane as vapour, so that no liquid water contacts the test specimen. With the test specimen placed on the membrane, the heat flux required to maintain a constant temperature at the plate is a measure of the rare of water evaporation, and from this the water-vapour resistance of the test specimen is determined.
The technique described in this International Standard enables the water-vapour resistance Ret of a material to be determined by subtracting the water-vapour resistance of the boundary air layer above the surface of the test apparatus from that of a test specimen plus boundary air layer, both measured under the same conditions.
5 Apparatus
5.1 Measuring unit, with temperature and water supply control, consisting of a metal plate approximately 3 mm thick with a minimum area of 0,04 m2 (e.g. a square with each side 200 mm in length, 1) fixed to a conductive metal block containing an electrical heating element [see Figure 1. items (1) and (6)1. For the measurement of water-vapour resistance, the metal plate (1) must be porous. It is surrounded by a thermal guard [item (8) of Figure 21 which is in turn located within an opening in a measuring table (11).
The coefficient of radiant emissivity of the plate surface (1) shall be greater than 0.35, measured at 20 °C between the wavelengths 8 pm to 14 pm, with the primary beam perpendicular to the plate surface and the reflection hemispherical.
Channels are machined into the face of the heating element block (6) where it contacts the porous plate to enable water to be fed from a dosing device (5).
The position of the measuring unit with respect to the measuring table shall be adjustable, so that the upper surface of test specimens placed on it can be made coplanar with the measuring table.
Heat losses from the wiring to the measuring unit or to its temperature measuring device should be minimized, e.g. by leading as much wiring as possible along the inner face of the thermal guard (8).BS EN ISO 11092 pdf download.