1、Designation: C 335 05ae1Standard Test Method forSteady-State Heat Transfer Properties of Pipe Insulation1This standard is issued under the fixed designation C 335; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEAdjunct references were corrected editorially in
3、April 2006.1. Scope1.1 This test method covers the measurement of the steady-state heat transfer properties of pipe insulations. Specimentypes include rigid, flexible, and loose fill; homogeneous andnonhomogeneous; isotropic and nonisotropic; circular or non-circular cross section. Measurement of me
4、tallic reflectiveinsulation and mass insulations with metal jackets or otherelements of high axial conductance is included; however,additional precautions must be taken and specified specialprocedures must be followed.1.2 The test apparatus for this purpose is a guarded-end orcalibrated-end pipe app
5、aratus. The guarded-end apparatus is aprimary (or absolute) method. The guarded-end method iscomparable, but not identical to ISO 8497.1.3 When appropriate, or as required by specifications orother test methods, the following thermal transfer propertiesfor the specimen can be calculated from the mea
6、sured data (see3.2):1.3.1 The pipe insulation lineal thermal resistance andconductance,1.3.2 The pipe insulation lineal thermal transference,1.3.3 The surface areal resistance and heat transfer coeffi-cient,1.3.4 The thermal resistivity and conductivity,1.3.5 The areal thermal resistance and conduct
7、ance, and1.3.6 The areal thermal transference.NOTE 1In this test method the preferred resistance, conductance, andtransference are the lineal values computed for a unit length of pipe. Thesemust not be confused with the corresponding areal properties computed ona unit area basis which are more appli
8、cable to flat slab geometry. If theseareal properties are computed, the area used in their computation must bereported.NOTE 2Discussions of the appropriateness of these properties toparticular specimens or materials may be found in Test Method C 177,Test Method C 518, and in the literature (1).21.4
9、This test method allows for operation over a wide rangeof temperatures. The upper and lower limit of the pipe surfacetemperature is determined by the maximum and minimumservice temperature of the specimen or of the materials used inconstructing the apparatus. In any case, the apparatus must beoperat
10、ed such that the temperature difference between theexposed surface and the ambient is sufficiently large enough toprovide the precision of measurement desired. Normally theapparatus is operated in closely controlled still air ambientfrom 15 to 30C, but other temperatures, other gases, and otherveloc
11、ities are acceptable. It is also acceptable to control theouter specimen surface temperature by the use of a heated orcooled outer sheath or blanket or by the use of an additionaluniform layer of insulation.1.5 The use any size or shape of test pipe is allowableprovided that it matches the specimens
12、 to be tested. Normallythe test method is used with circular pipes; however, its use ispermitted with pipes or ducts of noncircular cross section(square, rectangular, hexagonal, etc.). One common size usedfor interlaboratory comparison is a pipe with a circular crosssection of 88.9-mm diameter (stan
13、dard nominal 80-mm (3-in.)pipe size), although several other sizes are reported in theliterature (2-4).1.6 The test method applies only to test pipes with ahorizontal or vertical axis. For the horizontal axis, the literatureincludes using the guarded-end, the calibrated, and thecalibrated-end cap me
14、thods. For the vertical axis, no experi-ence has been found to support the use of the calibrated orcalibrated-end methods. Therefore the method is restricted tousing the guarded-end pipe apparatus for vertical axis mea-surements.1.7 This test method covers two distinctly different types ofpipe appar
15、atus, the guarded-end and the calibrated orcalculated-end types, which differ in the treatment of axial heattransfer at the end of the test section.1.7.1 The guarded-end apparatus utilizes separately heatedguard sections at each end, which are controlled at the same1This test method is under the jur
16、isdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved June 1, 2005. Published June 2005. Originallyapproved in 1954. Last previous edition approved in 2004 as C 335 05.2The boldface numbers in parent
17、heses refer to the references at the end of thistest method.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.temperature as the test section to limit axial heat transfer. Thistype of apparatus is preferred for all types of specimens w
18、ithinthe scope of this test method and must be used for specimensincorporating elements of high axial conductance.1.7.2 The calibrated or calculated-end apparatus utilizesinsulated end caps at each end of the test section to minimizeaxial heat transfer. Corrections based either on the calibrationof
19、the end caps under the conditions of test or on calculationsusing known material properties, are applied to the measuredtest section heat transfer. These apparatuses are not applicablefor tests on specimens with elements of high axial conductancesuch as reflective insulations or metallic jackets. Th
20、ere is noknown experience on using these apparatuses for measure-ments using a vertical axis.1.8 SI units are standard for this test method. Conversionfactors to other units are given in Table 1. The units used mustaccompany all numerical values.1.9 This standard does not purport to address all of t
21、hesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C 168 Terminology Relating
22、 to Thermal InsulationC 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC 302 Test Method for Density and Dimensions of Pre-formed Pipe-Covering-Type Thermal InsulationC 518 Test Method for Steady-State Thermal Tr
23、ansmissionProperties by Means of the Heat Flow Meter ApparatusC 680 Practice for Estimate of Heat Gain or Loss, andSurface Temperature of Insulated Flat, Cylindrical, andSpherical Systems by the Use of a Computer ProgramC 870 Practice for Conditioning of Thermal Insulating Ma-terialsC 1045 Practice
24、for Calculating Thermal TransmissionProperties Under Steady-State ConditionsE 230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized Thermocouples2.2 ISO Standards:ISO 8497 Thermal Insulation-Dermination of Steady StateThermal Transmission Properties of Thermal Insulation
25、for Circular Pipes2.3 ASTM Adjuncts:4Guarded-end ApparatusCalibrated-end Apparatus3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary pag
26、e onthe ASTM website.4Documents showing details of both guarded-end and calibrated-end apparatuscomplying with the requirements of this method are available from ASTM for anominal fee. Order Adjunct: ADJC033501 for the Guarded-End Apparatus andAdjunct: ADJC033502 for the Calibrated-End Cap Apparatus
27、.TABLE 1 Conversion Factors (International Table)NOTEFor thermal conductance per unit length or thermal transference per unit length, use the inverse of the table for thermal resistance per unit length.For thermal resistivity, use the inverse of the table for thermal conductivity. For thermal conduc
28、tance (per unit area) or thermal transference (per unit area),use the inverse of the table for thermal resistance (per unit area).Thermal Resistance per Unit LengthAKmW1(B)KcmW1Kcmscal1Kmhkg-cal1FfthBtu11 KmW1= 1.000 100.0 418.7 1.163 1.7311 KcmW1= 1.000 3 1021.000 4.187 1.163 3 1021.731 3 1021 Kcms
29、cal1= 2.388 3 1030.2388 1.000 2.778 3 1034.134 3 1031 Kmhkg-cal1= 0.8598 85.98 360.0 1.000 1.4881FfthBtu1= 0.5778 57.78 241.9 0.6720 1.000Thermal ConductivityAWm1K1(B)Wcm1K1cals1cm1K1kg-calh1m1K1Btuh1ft1F1Btuin.h1ft2F11Wm1K1= 1.000 1.000 3 1022.388 3 1030.8598 0.5778 6.9331 Wcm1K1= 100.0 1.000 0.238
30、8 85.98 57.78 693.31 cals1cm1K1= 418.7 4.187 1.000 360.0 241.9 2903.1 kg-calh1m1K1= 1.163 1.163 3 1022.778 3 1031.000 0.6720 8.0641 Btuh1ft1F1= 1.731 1.731 3 1024.134 3 1031.488 1.000 12.001 Btuin.h1ft2F1= 0.1442 1.442 3 1033.445 3 1040.1240 8.333 3 1021.000Thermal Resistance per Unit AreaAKm2W1(B)K
31、cm2W1Kcm2scal1Km2hkg-cal1Fft2hBtu11Km2W1= 1.000 1.000 3 1044.187 3 1041.163 5.6781 Kcm2W1= 1.000 3 1041.000 4.187 1.163 3 1045.678 3 1041 Kcm2scal1= 2.388 3 1050.2388 1.000 2.778 3 1051.356 3 1041Km2hkg-cal1= 0.8598 8.594 3 1033.600 3 1041.000 4.8821Fft2hBtu1= 0.1761 1.761 3 1037.373 3 1030.2048 1.0
32、00AUnits are given in terms of (1) the absolute joule per second or watt, (2) the calorie (International Table) = 4.1868 J, or the British thermal unit (InternationalTable) = 1055.06 J.BThis is the SI (International System of Units) unit.C 335 05ae123. Terminology3.1 DefinitionsFor definitions of te
33、rms used in this testmethod, refer to Terminology C 168.3.2 Definitions of Terms Specific to This Standard:3.2.1 areal thermal conductance, Cthe steady-state timerate of heat flow per unit area of a specified surface (Note 3)divided by the difference between the average pipe surfacetemperature and t
34、he average insulation outer surface tempera-ture. It is the reciprocal of the areal thermal resistance, R.C 5QAto2 t2!51R(1)where the surface of the area, A, must be specified (usuallythe pipe surface or sometimes the insulation outer surface).NOTE 3The value of C, the areal thermal conductance, is
35、arbitrarysince it depends upon an arbitrary choice of the area, A. For a homoge-neous material for which the thermal conductivity is defined as in 3.2.7(Eq 8), the areal conductance, C, is given as follows:C 52pLlpA ln r2/ro!(2)If the area is specially chosen to be the “log mean area,”equal to 2pL (
36、r2 ro)/l n (r2/ro), then C = lp/(r2 ro). Since (r2 ro) is equal to the insulation thickness measured from thepipe surface, this is analogous to the relation between conduc-tance and conductivity for flat slab geometry. Similar relationsexist for the areal thermal resistance defined in 3.2.2. Sinceth
37、ese areal coefficients are arbitrary, and since the area used isoften not stated, thus leading to possible confusion, it isrecommended that these areal coefficients not be used unlessspecifically requested.3.2.2 areal thermal resistance, Rthe average temperaturedifference between the pipe surface an
38、d the insulation outersurface required to produce a steady-state unit rate of heat flowper unit area of a specified surface (Note 3). It is the reciprocalof the areal thermal conductance, C.R 5Ato2 t2!Q51C(3)where the surface of the area, A, must be specified (usuallythe pipe surface or sometimes th
39、e insulation outer surface).3.2.3 areal thermal transference, Trthe time rate of heatflow per unit surface area of the insulation divided by thedifference between the average pipe surface temperature andthe average air ambient temperature.Tr5Q2pr2L to2 ta!(4)3.2.4 pipe insulation lineal thermal cond
40、uctance, CLthesteady-state time rate of heat flow per unit pipe insulationlength divided by the difference between the average pipesurface temperature and the average insulation outer surfacetemperature. It is the reciprocal of the pipe insulation linealthermal resistance, RL.CL5QLto2 t2!51RL(5)3.2.
41、5 pipe insulation lineal thermal resistance, RLtheaverage temperature difference between the pipe surface andthe insulation outer surface required to produce a steady-stateunit time rate of heat flow per unit of pipe insulation length. Itis the reciprocal of the pipe insulation lineal thermal conduc
42、-tance, CL.RL5Lto2 t2!Q51CL(6)3.2.6 pipe insulation lineal thermal transference, Trpthesteady-state time rate of heat flow per unit pipe insulationlength divided by the difference between the average pipesurface temperature and the average air ambient temperature. Itis a measure of the heat transfer
43、red through the insulation to theambient environment.Trp5QLto2 ta!(7)3.2.7 pipe insulation thermal conductivity,lpof homoge-neous material, the ratio of the steady-state time rate of heatflow per unit area to the average temperature gradient (tem-perature difference per unit distance of heat flow pa
44、th). Itincludes the effect of the fit upon the test pipe and is thereciprocal of the pipe insulation thermal resistivity, rL. For pipeinsulation of circular cross section, the pipe insulation thermalconductivity is:lp5Q 1n r2/ro!L2pto2 t2!51rL(8)3.2.8 pipe insulation thermal resistivity, rLof homoge
45、-neous material, the ratio of the average temperature gradient(temperature difference per unit distance of heat flow path) tothe steady-state time rate of heat flow per unit area. It includesthe effect of the fit upon the test pipe and is the reciprocal of thepipe insulation thermal conductivity, lp
46、. For pipe insulation ofcircular cross section, the pipe insulation thermal resistivity iscalculated as follows:rL52pLto2 t2!Q 1n r2/ro!51lp(9)3.2.9 surface areal heat transfer coeffcient, h2the ratio ofthe steady-state time rate of heat flow per unit surface area tothe average temperature differenc
47、e between the surface and theambient surroundings. The inverse of the surface heat transfercoefficient is the surface resistance. For circular cross sections:h25Q2pr2Lt22 ta!(10)3.3 Symbols: see 1.8:CL= pipe insulation lineal thermal conductance, W/mK,RL= pipe insulation lineal thermal resistance, K
48、m/W,Trp= pipe insulation lineal thermal transference, W/mK,lp= pipe insulation thermal conductivity, W/mK,rL= pipe insulation thermal resistivity, Km/W,h2= surface areal heat transfer coefficient of insulationouter surface, W/m2K,C = areal thermal conductance, W/m2K,R = areal thermal resistance, Km2
49、/W,Tr= areal thermal transference, W/m2K,Q = time rate of heat flow to the test section of length L,W,to= temperature of pipe surface, K,C 335 05ae13t1= temperature of insulation inside surface, K,t2= temperature of insulation outside surface, K,ta= temperature of ambient air or gas, K,ro= outer radius of circular pipe, m,r1= inner radius of circular insulation, m,r2= outer radi
