BS 4745-2005 Determination of the thermal resistance of textiles - Two-plate method fixed pressure procedure two-plate plate method fixed opening procedure and single-plate method《.pdf

1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58method: fixed pressure procedure, two-plate method: fixed opening procedure, and single-plate metho

2、dICS 59.080.01Determination of the thermal resistance of textiles Two-plate BRITISH STANDARDBS 4745:2005BS 4745:2005This British Standard was published under the authority of the Standards Policy and Strategy Committee on 25 November 2005 BSI 25 November 2005The following BSI references relate to th

3、e work on this standard:Committee reference TCI/24ISBN 0 580 46777 5British Apparel and Textile ConfederationBritish Measurement and Testing AssociationBritish Textile Machinery AssociationBritish Textile Technology GroupDefence Procurement AgencyFurniture Industry Research AssociationNational Wool

4、Textile Export CorporationS A T R A Technology CentreSociety of Dyers and ColouristsTextile InstituteUK Textile Laboratories ForumWoolmark CompanyCo-opted membersAmendments issued since publicationAmd. No. Date CommentsCommittees responsible for this British StandardThe preparation of this British S

5、tandard was entrusted to Technical Committee TCI/24, Physical testing of textiles, upon which the following bodies were represented:Association of Consulting ScientistsAssociation of Suppliers to the British Clothing IndustryBS 4745:2005 BSI 25 November 2005ContentsPageCommittees responsible Inside

6、front coverForeword ii1Scope 12 Normative references 13 Terms and definitions 14Units 25 Principle 26 Apparatus 27Calibration of the standard thermal resistance 48 Atmosphere for conditioning and testing 49 Test specimens 410 Procedure 511 Calculation and expression of results 612 Test report 7Annex

7、 A (normative) Calibration of standard thermal resistance 8Annex B (normative) Thermal conductivity 8Annex C (informative) Accuracy 8Bibliography 9Figure 1 Diagram of the apparatus 3Figure 2 Side elevation of cabinet 4iBS 4745:2005iisupersedes BS 4745:1990, which has been withdrawn. The method has b

8、een derived from ISO 5085-1:1989, Textile determination of thermal resistance of textiles Part 1: Low thermal resistance, and has been modified by TCI/24.Three methods for the determination of thermal resistance are described, as referred to in the scope. The method used must be agreed between inter

9、ested parties because the results from the different methods are not necessarily comparable.Related standards are: ISO 5085-2, Textiles Determination of thermal resistance of textiles Part 2: High thermal resistance. BS 874-1, BS 874-3.1, BS 874-3.2: Methods for determining thermal insulation proper

10、ties.This new edition of BS 4745 incorporates technical changes only. It does not reflect a full review or revision of the standard, which will be undertaken in due course.A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are respon

11、sible for their correct application.Compliance with a British Standard does not of itself confer immunity from legal obligations.Summary of pagesThis document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 9 and a back cover.The BSI copyright notice displayed in this docu

12、ment indicates when the ForewordThis British Standard has been prepared by Technical Committee TCI/24. It BSI 25 November 2005document was last issued.BS 4745:20051 ScopeThis part of BS 4745 specifies three methods for the determination of the resistance of fabrics, fabric assemblies or fibre aggreg

13、ates in sheet form to the transmission of heat through them in the steady state condition. It applies to materials whose thermal resistance is up to approximately 0.2 m2K/W.These methods are suitable for materials up to 20 mm thick (above this thickness, edge losses become appreciable). Advice on su

14、itable components for constructing the apparatus is given in Annex A and means of calculating the thermal conductivity are described in Annex B.Three methods are described:a) two-plate method: fixed pressure procedure;b) two-plate method: fixed opening procedure;c) single-plate method.Either of the

15、two-plate methods is suitable for materials that, when in use, have their outer faces shielded from the ambient air, e.g a blanket when covered by a bedspread.The single-plate method is suitable for materials that, when in use, have their outer faces exposed to the ambient air (e.g. bedspreads and o

16、uterwear).The two-plate methods are generally preferred on accuracy and reproducibility grounds. 2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the reference cited applies. For undated references, the latest

17、 edition of the referenced document (including any amendments) applies.BS EN ISO 5084, Textiles Determination of thickness of textiles and textile products.ISO 139, Textiles Standard atmospheres for conditioning and testing.ISO 8302, Thermal insulation Determination of steady-state thermal resistanc

18、e and related properties Guarded hot plate apparatus.3 Terms and definitionsFor the purposes of this British Standard, the following terms and definitions apply.3.1 thermal resistanceRratio of the temperature difference between the two faces of a test specimen to the rate of flow of heat per unit ar

19、ea normal to the faces. It is analogous to electrical resistance in the case of current flow through an electrical conductor3.2 thermal conductivitykquantity of heat that passes in unit time through unit area of a slab of infinite extent and of unit thickness when unit difference of temperature exis

20、ts between the faces of the slabNOTE 1 whered is the thickness of the slab.NOTE 2 For a flat material having parallel faces, thermal conductivity is the reciprocal of thermal resistance per unit thickness .NOTE 3 Since a textile is a heterogeneous system consisting of fibres and air, the term therma

21、l conductivity does not have its usual Rdk-= BSI 25 November 20051precise meaning since, in addition to conduction, heat can be transferred through a textile by radiation and possibly by convection. The heat transfer rate incorporated in the definition is therefore the overall transfer by conduction

22、 and by radiation (and by convection where applicable).BS 4745:20053.3 togmeterequipment described in 6.14 UnitsThe SI unit of thermal resistance R is the square-metre kelvin per watt (m2K/W).NOTE A practical unit of thermal resistance, widely used in the field of textiles and clothing, is the tog:

23、1 tog = 0.1 m2K/W.The SI unit of thermal conductivity k is the watt per metre kelvin W/(mK).5 PrincipleThe temperature drop across a material of known thermal resistance (the standard resistance) and across a specimen of the material under test in series with it are measured and the thermal resistan

24、ce of the specimen is determined from the values obtained.The principle of the apparatus is that, for conductors in series with respect to the direction of heat flow, the ratio of the temperature drop across the conductors is equal to the ratio of their thermal resistance.6 Apparatus6.1 GeneralThe a

25、pparatus shall be as shown in Figure 1. The apparatus shall be horizontal, with the heat flow upwards, designed so that the measurements are made with the test specimen in the horizontal position.6.2 Principal parts6.2.1 Mild-steel disc (A), 330 mm in diameter and approximately 6 mm thick, which has

26、 been annealed to relieve internal stresses.6.2.2 Electric heaters (B1 and B2), clamped to the lower face of the disc A to give an even distribution of heat and capable of maintaining the temperature specified in 9.1 and 9.2.6.2.3 Disc of insulating board (C), of thermal resistance within the range

27、0.075 m2K/W to 0.125 m2K/W and of thickness between 5 mm and 25 mm. The disc shall be 330 mm in diameter and in contact with the hot plate of the apparatus. The surfaces of the disc shall be smooth, flat and parallel.6.2.4 Cold plate (D), the surfaces of which shall be smooth, flat and parallel, and

28、 which results in an applied pressure of 6.9 Pa over the whole of the area of 855 cm2, i.e. a circle of diameter (330 1) mm. Fixed pressure method: In the case of the fixed pressure method, the plate shall be made of a suitably light material so that the mass of the plate itself, when resting on the

29、 specimen, provides the required pressure of 6.9 Pa. In use, the plate shall be placed gently on top of the specimen, taking care not to compress the specimen. Fixed opening method: Using a suitable thickness gauge, the thickness of the test specimen shall be measured under a pressure of 6.9 Pa. Thr

30、ee thickness gauges shall be placed at regular intervals around the edge of the top plate. The thickness gauges shall be set to the measured thickness of the specimen and the coldplate shall be placed on top.6.2.5 Insulation (E), to reduce heat wastage.6.2.6 Temperature sensors (T1, T2and T3). These

31、 sensors shall be 0.20 mm to 0.315 mm diameter copper-constantan thermocouples, calibrated to 0.01 K, or equally accurate sensors of similar size. The temperature sensors shall be fixed permanently in good thermal contact with separate 25 mm diameter discs of approximately 0.1 mm thick copper foil,

32、which are fixed, with an epoxy-resin or similar adhesive, in small grooves in the surfaces of the disc C and the cold plate D. Aluminium foil discs, 0.006 mm thick 2 BSI 25 November 2005and 140 mm in diameter, shall be stuck centrally over sensors T2and T3, the whole of the exposed faces of C and D

33、shall be painted with dull black lacquer to ensure an emissivity approaching unity.NOTE A suitable indicator device or recorder is recommended for recording temperatures.BS 4745:20056.2.7 Automatic temperature control, achieved by means of a temperature-sensitive element (M), incorporated in a contr

34、ol system.6.3 CabinetThe apparatus shall be enclosed in the cabinet as shown in Figure 2. NOTE The cabinet provides a shield against neighbouring sources of radiant heat and controlled ventilation across the face of the apparatus.The extractor fan shall draw air past the apparatus from the standard

35、atmosphere in the room through an adjustable slot at the other end of the cabinet. The fan characteristics shall be such that the air speed past the test specimen is within the range 0.25 m/s to 1 m/s.Dimensions in millimetresKey1 Plan2 SectionFigure 1 Diagram of the apparatus1 2B M E AB2 1TDCT31T20

36、 50 100 150 200 250 BSI 25 November 20053BS 4745:20057 Calibration of the standard thermal resistanceCalibrate the standard thermal resistance by one of the following procedures.a) Conduct tests with samples of known thermal resistance, treating the standard thermal resistance as the unknown quantit

37、y to be evaluated, as described in 10.1 and 11.2.b) Use the method described in Annex A.c) Use a guarded hot plate apparatus conforming to ISO 8302 to measure the heat flow, with the mean temperature of the standard thermal resistance being between 309 K and 313 K.NOTE The temperature drop should be

38、 measured with an external calibrated thermocouple as opposed to the thermocouples that form part of the togmeter.8 Atmosphere for conditioning and testingThe conditioning and testing atmosphere shall be one of the standard atmospheres for testing textiles defined in ISO 139.9 Test specimensAll dime

39、nsions in millimetres and approximateKey1 Observation window2 Air flow3 Extractor fan (air speed past specimen: 0.25 m/s min., 1 m/s max.)Figure 2 Side elevation of cabinet4501 2007501234 BSI 25 November 2005Cut circular test specimens of diameter 330 mm, avoiding creases and folds. Condition them b

40、y laying them flat in the standard atmosphere for testing textiles for 24 h. Where possible, test three specimens of each sample.BS 4745:200510 Procedure10.1 Two-plate method: Fixed pressure procedureLay the conditioned test specimen on the hot plate of the apparatus and place the cold plate gently

41、on top of it, taking care not to compress the surface of the test specimen. Shield the edges from the airflow, e.g. by wrapping a strip of woven blanket or masking tape round the apparatus.Switch on the electric heaters and adjust the temperature controller so that T2registers a temperature within t

42、he range 304 K to 308 K. Maintain a steady state of temperature at each of the thermocouple sites T1, T2and T3for a period of not less than 30 min before considering a test to be completed, and ensure that the fluctuations in the various temperature levels do not exceed 0.1 K throughout this period.

43、NOTE For materials of low bulk density (e.g. blankets), the duration of a test from the switching on of the heaters, and including the steady state period, is approximately two hours but, for denser materials, it will be longer (approximately three hours).Record, to the nearest 0.01 K, the temperatu

44、res registered by T1, T2and T3.10.2 Two-plate method: fixed opening procedureUsing a suitable thickness gauge, measure the thickness of the specimen according to BS EN ISO 5084 under a pressure of 6.9 Pa. Set the three thickness gauges on the top plate to this measured thickness. Lay the conditioned

45、 test specimen on the hot plate of the apparatus and place the top plate on top. Shield the edges from the airflow, e.g. by wrapping a strip of woven blanket or masking tape round the apparatus.Switch on the electric heaters and adjust the temperature controller so that T2registers a temperature wit

46、hin the range 304 K to 308 K. Maintain a steady state of temperature at each of the thermocouple sites T1, T2and T3for a period of not less than 30 min before considering a test to be completed, and ensure that the fluctuations in the various temperature levels do not exceed 0.1 K throughout this pe

47、riod.For materials of low bulk density (e.g. blankets), the duration of a test from the switching on of the heaters, and including the steady-state period, is approximately two hours but, for denser materials, it will be longer (approximately three hours).Note, to the nearest 0.01 K, the temperature

48、s registered by T1, T2and T3.10.3 Single-plate methodLay the conditioned test specimen on the hot plate (with the edges shielded) but leave its outer face uncovered and place the cold plate underneath the apparatus. Support the cold plate, e.g. by three corks, to allow air circulation and cover with

49、 a circular piece of hardboard or metal sheet to the upper face of which a sheet of aluminium foil has been stuck in order to shield the cold plate from the radiant heat emitted by the apparatus. T3is now used to measure the air temperature.Record, to the nearest 0.01 K, the temperatures registered by T1, T2and T3. Repeat the test without a test specimen (i.e. conduct a bare-plate test). BSI 25 November 20055BS 4745:200511 Calculation and expression of results11.1 Contact resistanceNOTE Because of the fin