ASTM C1045-2001 Standard Practice for Calculating Thermal Transmission Properties Under Steady-State Conditions《在稳态条件下计算热传递性能的标准规程》.pdf

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1、Designation: C 1045 01Standard Practice forCalculating Thermal Transmission Properties Under Steady-State Conditions1This standard is issued under the fixed designation C 1045; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye

2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides the user with a uniform procedurefor calculating the thermal transmission properties of

3、a materialor system from data generated by steady state, one dimensionaltest methods used to determine heat flux and surface tempera-tures. This practice is intended to eliminate the need for similarcalculation sections in Test Methods C 177, C 335, C 518,C 976, C 1033, C 1114 and C 1363 by permitti

4、ng use of thesestandard calculation forms by reference.1.2 The thermal transmission properties described include:thermal conductance, thermal resistance, apparent thermalconductivity, apparent thermal resistivity, surface conductance,surface resistance, and overall thermal resistance or transmit-tan

5、ce.1.3 This practice provides the method for developing theapparent thermal conductivity as a function of temperaturerelationship for a specimen from data generated by standardtest methods at small or large temperature differences. Thisrelationship can be used to characterize material for compari-so

6、n to material specifications and for use in calculationprograms such as Practice C 680.1.4 The SI unit values used in this practice are consideredstandard.1.5 This practice includes a discussion of the definitions andunderlying assumptions for the calculation of thermal trans-mission properties. Tes

7、ts to detect deviations from theseassumptions are described. This practice also considers thecomplicating effects of uncertainties due to the measurementprocesses and material variability. See Section 7.1.6 This practice is not intended to cover all possible aspectsof thermal properties data base de

8、velopment. For new materi-als, the user should investigate the variations in thermalproperties seen in similar materials. The information containedin Section 7, the Appendix and the technical papers listed in theReferences section of this practice may be helpful in determin-ing whether the material

9、under study has thermal propertiesthat can be described by equations using this practice. Someexamples where this method has limited application include:(1) the onset of convection in insulation as described inReference (21);(2) a phase change of one of the insulationsystem components such as a blow

10、ing gas in foam; and (3) theinfluence of heat flow direction and temperature differencechanges for reflective insulations.2. Referenced Documents2.1 ASTM Standards:C 168 Terminology Relating to Thermal Insulating Materi-als2C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Trans

11、mission Properties by Means ofthe Guarded-Hot-Plate Apparatus2C 335 Test Method for Steady-State Heat Transfer Proper-ties of Horizontal Pipe Insulations2C 518 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Heat Flow Meter Apparatus2C 680 Prac

12、tice for Determination of Heat Gain or Loss andthe Surface Temperature of Insulated Pipe and EquipmentSurfaces by the Use of a Computer Program2C 976 Test Method for Steady-State Thermal Performanceof Building Assemblies by Means of a Calibrated Hot Box2C 1033 Test Method for Steady-State Heat Trans

13、fer Prop-erties of Pipe Insulation Installed Vertically2C 1058 Practice for Selecting Temperatures for Evaluatingand Reporting Properties of Thermal Insulation2C 1114 Test Method for Steady-State Thermal TransmissionProperties by Means of the Thin-Heater Apparatus2C 1199 Test Method for Measuring th

14、e Steady-State Ther-mal Transmittance of Fenestration Systems Using Hot BoxMethods2C 1363 Test Method for Thermal Performance of BuildingAssemblies by Means of a Hot Box Apparatus2E 122 Practice for Choice of Sample Size to Estimate theAverage Quality of a Lot or Process33. Terminology3.1 Definition

15、s The definitions and terminology of thispractice are intended to be consistent with Terminology C 168.However, because exact definitions are critical to the use of this1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommitte

16、e C16.30 on ThermalMeasurements.Current edition approved March 10, 2001. Published June 2001. Originallypublished as C 1045 85. Last previous edition C 1045 97.2Annual Book of ASTM Standards, Vol 04.06.3Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocke

17、n, PA 19428-2959, United States.practice, the following equations are defined here for use in thecalculations section of this practice.3.2 SymbolsThe symbols, terms and units used in thispractice are the following:A = specimen area normal to heat flux direction, m2,C = thermal conductance, W/(m2 K),

18、hc= surface heat transfer coefficient, cold side,W/(m2 K),hh= surface heat transfer coefficient, hot side,W/(m2 K),L = thickness of a slab in heat transfer direction, m,Lp= metering area length in the axial direction, m,q = one-dimensional heat flux (time rate of heat flowthrough metering area divid

19、ed by the apparatusmetering area A), W/m2,Q = time rate of one-dimensional heat flow throughthe metering area of the test apparatus, W,r = thermal resistivity, K m/K,ra= apparent thermal resistivity, K m/K,rin= inside radius of a hollow cylinder, m,rout= outside radius of a hollow cylinder, m,R = th

20、ermal resistance, m2 K/W,Rc= surface thermal resistance, cold side, m2 K/W,Rh= surface thermal resistance, hot side, m2 K/W,Ru= overall thermal resistance, m2 K/W,T = temperature, K,T1= area-weighted air temperature 75 mm or morefrom the hot side surface, K,T2= area-weighted air temperature 75 mm or

21、 morefrom the cold side surface, K,Tc= area-weighted temperature of the specimen coldsurface, K,Th= area-weighted temperature of specimen hot sur-face, K,Tin= temperature at the inner radius, K,Tm= specimen mean temperature, average of two op-posite surface temperatures, (Th+ Tc)/2, K,Tout= temperat

22、ure at the outer radius, K,DT = temperature difference, K,DTa-a= temperature difference, air to air, ( T1 T2), K,DTs-s= temperature difference, surface to surface,(Th Tc), K,U = thermal transmittance, W/(m2 K), andx = linear dimension in the heat flow direction, m,l = thermal conductivity, W/(m K),l

23、a= apparent thermal conductivity, W/(m K),l(T) = the functional relationship between thermal con-ductivity and temperature, W/(m K),lexp= the experimental thermal conductivity,W/(m K),lm= mean thermal conductivity, averaged with respectto temperature from Tcto Th, W/(m K), (seesections 6.4.1 and App

24、endix X3).NOTE 1Subscripts h and c are used to differentiate between hot sideand cold side surfaces.3.3 Thermal Transmission Property Equations:3.3.1 Thermal Resistance, R, is defined in TerminologyC 168. It is not necessarily a unique function of temperature ormaterial, but is rather a property det

25、ermined by the specificthickness of the specimen and by the specific set of hot-sideand cold-side temperatures used to measure the thermal resis-tance.R 5A Th Tc!Q(1)3.3.2 Thermal Conductance, C:C 5QA Th2 Tc!51R(2)NOTE 2Thermal resistance, R, and the corresponding thermal con-ductance, C, are recipr

26、ocals; that is, their product is unity. These termsapply to specific bodies or constructions as used, either homogeneous orheterogeneous, between two specified isothermal surfaces.NOTE 3Eq 1, Eq 2, and Eq 11-13 are for rectangular coordinatesystems only. Similar equations for resistance, etc. can be

27、 developed for acylindrical coordinate system providing the difference in areas is consid-ered. In practice, for cylindrical systems such as piping runs, the thermalresistance should be based upon the pipe external surface area since thatarea does not change with different insulation thickness.3.3.3

28、 Apparent thermal conductivity, la, is defined in Ter-minology C 168.Rectangular coordinates:la5QLA Th2 Tc!(3)Cylindrical coordinates:la5Q lnrout/rin!2 p LpTin2 Tout!(4)3.3.4 Apparent Thermal Resistivity,ra, is defined in Termi-nology C 168.Rectangular Coordinates:ra5A Th2 Tc!QL51la(5)Cylindrical Co

29、ordinates:ra52 p LpTin2 Tout!Q ln rout/ rin!51la(6)NOTE 4The apparent thermal resistivity, ra, and the correspondingthermal conductivity, la, are reciprocals, that is, their product is unity.These terms apply to specific materials tested between two specifiedisothermal surfaces. For this practice, m

30、aterials are considered homoge-neous when the value of the thermal conductivity or thermal resistivity isnot significantly affected by variations in the thickness or area of thesample within the normally used range of those variables.3.4 Transmission Property Equations for ConvectiveBoundary Conditi

31、ons:3.4.1 Surface Thermal Resistance, Ri, the quantity deter-mined by the temperature difference at steady-state between anisothermal surface and its surrounding air that induces a unitheat flow rate per unit area to or from the surface. Typically,this parameter includes the combined effects of cond

32、uction,convection, and radiation. Surface resistances are calculated asfollows:Rh5A T12 Th!Q(7)Rc5A Tc2 T2!Q(8)C 104523.4.2 Surface Heat Transfer Coeffcient, hi, is often calledthe film coefficient. These coefficients are calculated as fol-lows:hh5QA T12 Th!51Rh(9)hc5QA Tc2 T2!51Rc(10)NOTE 5The surf

33、ace heat transfer coefficient, hi, and the correspondingsurface thermal resistance, Ri, are reciprocals, that is, their product isunity. These properties are measured at a specific set of ambient conditionsand are therefore only correct for the specified conditions of the test.3.4.3 Overall Thermal

34、Resistance, RuThe quantity deter-mined by the temperature difference, at steady-state, betweenthe air temperatures on the two sides of a body or assembly thatinduces a unit time rate of heat flow per unit area through thebody. It is the sum of the resistance of the body or assemblyand of the two sur

35、face resistances and may be calculated asfollows:Ru5A T12 T2!Q(11)5 Rc1 R 1 Rh3.4.4 Thermal Transmittance, U (sometimes called overallcoefficient of thermal transfer), is calculated as follows:U 5QA T1 T2!51Ru(12)The transmittance can be calculated from the thermal con-ductance and the surface coeff

36、icients as follows:1/U 5 1/hh! 1 1/C! 1 1/hc! (13)NOTE 6Thermal transmittance, U, and the corresponding overallthermal resistance, Ru, are reciprocals; that is, their product is unity. Theseproperties are measured at a specific set of ambient conditions and aretherefore only correct for the specifie

37、d conditions of the test.4. Significance and Use4.1 ASTM thermal test method descriptions are complexbecause of added apparatus details necessary to ensure accurateresults. As a result, many users find it difficult to locate the datareduction details necessary to reduce the data obtained fromthese t

38、ests. This practice is designed to be referenced in thethermal test methods, thus allowing those test methods toconcentrate on experimental details rather than data reduction.4.2 This practice is intended to provide the user with auniform procedure for calculating the thermal transmissionproperties

39、of a material or system from standard test methodsused to determine heat flux and surface temperatures. Thispractice is intended to eliminate the need for similar calculationsections in the ASTM Test Methods (C 177, C 335, C 518,C 976, C 1033, C 1114, C 1199, and C 1363) by permitting useof these st

40、andard calculation forms by reference.4.3 This practice provides the method for developing thethermal conductivity as a function of temperature for aspecimen from data taken at small or large temperaturedifferences. This relationship can be used to characterizematerial for comparison to material spe

41、cifications and for usein calculations programs such as Practice C 680.4.4 Two general solutions to the problem of establishingthermal transmission properties for application to end-useconditions are outlined in Practice C 1058. (Practice C 1058should be reviewed prior to use of this practice.) One

42、is tomeasure each product at each end-use condition. This solutionis rather straightforward, but burdensome, and needs no otherelaboration. The second is to measure each product over theentire temperature range of application conditions and to usethese data to establish the thermal transmission prop

43、ertydependencies at the various end-use conditions. One advantageof the second approach is that once these dependencies havebeen established, they serve as the basis for estimating theperformance for a given product at other conditions.4.5 PrecautionThe use of a thermal conductivity curvedeveloped i

44、n Section 6 must be limited to a temperature rangethat does not extend beyond the range of highest and lowesttest surface temperatures in the test data set used to generatethe curve.5. Determination of Thermal Transmission Properties fora Specific Set of Temperature Conditions5.1 Choose the thermal

45、test parameter (l or r, R or C, U orRu) to be calculated from the test results. List any additionalinformation required by that calculation i.e. heat flux, tempera-tures, dimensions. Recall that the selected test parameter mightlimit the selection of the thermal test method used in 5.2.5.2 Select th

46、e appropriate test method that provides thethermal test data that can be used to determine the thermaltransmission property of interest for the sample material beingstudied. (See referenced papers and Appendix X1 for help withthis determination.5.3 Using that test method, determine the required stea

47、dy-state heat flux and temperature data at the selected testcondition.NOTE 7The calculation of specific thermal transmission propertiesrequires that: (1) the thermal insulation specimen is homogeneous, asdefined in Terminology C 168 or, as a minimum, appears uniform acrossthe test area; (2) the meas

48、urements are taken only after steady-state hasbeen established; ( 3) the heat flows in a direction normal to the isothermalsurfaces of the specimen; (4) the rate of flow of heat is known; (5) thespecimen dimensions, that is, heat flow path length parallel to heat flow,and area perpendicular to heat

49、flow, are known; and (6) both specimensurface temperatures (and equivalently, the temperature difference acrossthe specimen) are known; and in the case of a hot box systems test, bothair curtain temperatures must be known.5.4 Calculate the thermal property using the data gathered in5.2 and 5.3, and the appropriate equation in 3.3 or 3.4 above.The user of this practice is responsible for insuring that theinput data from the tests conducted are consistent with thedefined properties of the test parameter prior to parametercalculation.