BS ISO 20852:2020 pdf free.Textiles — Determination of the total heat transferthrough textiles in simulated environments.
This document specifies the test method for determining the amount of heat transferred throughclothing fabrics by the combined dry and evaporative heat emission under simulated and specifiedconditions. This test method can be used for fabrics, films, coatings, foams and leathers includingmultilayer assemblies used in hot environment or in activities.
The application of this measurement technique is restricted to a maximum amount of total heat transferwhich depend on the dimensions and construction of the apparatus used (e.g.about 1200 W/m2 for themaximum specifications of the equipment according to Iso 11092).
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references,only the edition cited applies.Forundated references, the latest edition of the referenced document (including any amendments] applies.ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 11092:2014,Textiles — Physiological effects —Measurement of thermal and water-vapour resistanceunder steady-state conditions (sweating guarded-hotplate test).For the purposes of this document, the following terms and definitions apply.
heat transferred by the temperature difference between the two faces of a material divided by theresultant heat flux per unit area in the direction of the gradient in dry state.heat transferred by the water-vapour pressure difference between the two faces of a material dividedby the resultant evaporative heat flux per unit area in the direction of the gradient,when evaluatednon-isothermally.
This test evaluates two forms of heat transfer which are dry heat and evaporative heat emission. Thetotal heat transfer results from combining both by calculation. Dry heat emission represents the heatloss resulting from the external environment due to the temperature gradient 10 °C and it is drawn fromthe standardized total thermal resistance of the test specimen and air layer. Evaporative heat emissionrepresents the heat loss resulting from the external environment due to the vapour pressure gradient3,57 kPa and it is drawn from the standardized total evaporative resistance of the test specimen andair layer.For the evaporative resistance measurements,water for analytical laboratory use over grade 3,according to ISO 3696, shall be used to wet the test plate surface.
A smooth, water-vapour permeable but liquid-water impermeable cellophane membrane of thickness10 um to 50 um shall be fitted over the porous plate.
Three test specimens are used.Use test specimens large enough to cover the surface of the hot plate testsection and the guard section completely.Remove any undesirable wrinkles from the test specimens.Possible techniques for removing wrinkles include smoothing,free-hanging, pressing，steaming,ironing, and so forth. Allow the test specimens to come into equilibrium with the atmosphere 25 C,65%R.H. of the testing chamber after conditioning them at the same environment for at least 12 h.BS ISO 20852 pdf download.