1、Designation: C335/C355M 10Standard Test Method forSteady-State Heat Transfer Properties of Pipe Insulation1This standard is issued under the fixed designation C335/C355M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers the measureme
3、nt 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 metallic reflectiveinsulation and mass insulations with metal
4、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 apparatus. The guarded-end apparatus is aprimary (or absolute)
5、method. The guarded-end method iscomparable, but not identical to ISO 8497.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the oth
6、er. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 When appropriate, or as required by specifications orother test methods, the following thermal transfer propertiesfor the specimen can be calculated from the measured data (see3.2):1.4.1 The pipe insulation l
7、ineal thermal resistance andconductance,1.4.2 The pipe insulation lineal thermal transference,1.4.3 The surface areal resistance and heat transfer coeffi-cient,1.4.4 The thermal resistivity and conductivity,1.4.5 The areal thermal resistance and conductance, and1.4.6 The areal thermal transference.N
8、OTE 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 applicable to flat slab geometry. If theseareal prop
9、erties 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 C177, TestMethod C518, and in the literature (1).21.5 This test method allows for operation over a wide
10、 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 beoperated such that the temperature difference between t
11、heexposed 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 othervelocities are acceptable. It is also acceptable to co
12、ntrol 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.1.6 The use any size or shape of test pipe is allowableprovided that it matches the specimens to be tested. Normallythe test method is used wi
13、th 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 (standard nominal 80-mm 3-in.pipe size), although seve
14、ral other sizes are reported in theliterature (2-4).1.7 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 methods. For the vertical axis, no experi-ence has be
15、en 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.1.8 This test method covers two distinctly different types ofpipe apparatus, the guarded-end and the calibrated orcalculat
16、ed-end types, which differ in the treatment of axial heattransfer at the end of the test section.1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved June 1, 2010.
17、Published October 2010. Originallyapproved in 1954. Last previous edition approved in 2005 as C335 05a1. DOI:10.1520/C0335_C0335M-10.2The boldface numbers in parentheses refer to the references at the end of thistest method.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
18、hohocken, PA 19428-2959, United States.1.8.1 The guarded-end apparatus utilizes separately heatedguard sections at each end, which are controlled at the sametemperature as the test section to limit axial heat transfer. Thistype of apparatus is preferred for all types of specimens withinthe scope of
19、this test method and must be used for specimensincorporating elements of high axial conductance.1.8.2 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 the end caps under
20、 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. There is noknown exp
21、erience on using these apparatuses for measure-ments using a vertical axis.1.9 This standard does not purport to address all of thesafety 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 determin
22、e the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C168 Terminology Relating to Thermal InsulationC177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC302 Test Meth
23、od for Density and Dimensions of Pre-formed Pipe-Covering-Type Thermal InsulationC518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusC680 Practice for Estimate of the Heat Gain or Loss and theSurface Temperatures of Insulated Flat, Cylindrical, a
24、ndSpherical Systems by Use of Computer ProgramsC870 Practice for Conditioning of Thermal Insulating Ma-terialsC1045 Practice for CalculatingThermalTransmission Prop-erties Under Steady-State ConditionsC1058 Practice for Selecting Temperatures for Evaluatingand Reporting Thermal Properties of Thermal
25、 InsulationE230 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 Insulationfor Circular Pipes2.3 ASTM Adjuncts:4Guarded-end ApparatusCalibrat
26、ed-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 page onthe ASTM website.4Documents showing details of both guarded-en
27、d 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.TABLE 1 Conversion Factors (International Table)NOTEFor thermal c
28、onductance 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 conductance (per unit area) or thermal transference (per unit area),use
29、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 Kcmscal1= 2.388 3 1030.2388 1.000 2.778 3 1034.134 3 1031 Kmhkg-cal1=
30、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 0.2388 85.98 57.78 693.31 cals1cm1K1= 418.7 4.187 1.000 360.0 241.9 290
31、3.1 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)Kcm2W1Kcm2scal1Km2hkg-cal1Fft2hBtu11Km2W1= 1.000 1.000 3 1044.187 3
32、 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 1.000AUnits are given in terms of (1) the absolute joule per second o
33、r 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.C335/C355M 1023. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology C168.3.2 Defin
34、itions 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 the average insulation outer surface tempera-ture. It is the recip
35、rocal 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 arbitrarysince it depends upon an arbitrary choice of the area, A
36、. 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 (r2 ro)/l n (r2/ro), then C = lp/(r2 ro). Since (r2 ro) is equal t
37、o 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. Sincethese areal coefficients are arbitrary, and since the area used iso
38、ften 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 and the insulation outersurface required to produce a steady-state
39、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 the insulation outer surface).3.2.3 areal thermal transference, Trt
40、he 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 conductance, CLthesteady-state time rate of heat flow per unit pipe i
41、nsulationlength 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)3.2.5 pipe insulation lineal thermal resistance, RLtheaverage tempera
42、ture 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-tance, CL.RL5Lto2 t2!Q51CL(6)3.2.6 pipe insulation lineal therma
43、l 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 transferred through the insulation to theambient environment.Trp5QLto2 ta
44、!(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 path). Itincludes the effect of the fit upon the test pipe and is t
45、hereciprocal 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-neous material, the ratio of the average temperature gradient(te
46、mperature 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. For pipe insulation ofcircular cross section, the pipe insulati
47、on 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 difference between the surface and theambient surroundings. The inverse of
48、 the surface heat transfercoefficient is the surface resistance. For circular cross sections:h25Q2pr2Lt22 ta!(10)3.3 Symbols: see 1.3:CL= pipe insulation lineal thermal conductance, W/mKBtuin/Fhrft2,RL= pipe insulation lineal thermal resistance, Km/WBtuin/Fhrft2,Trp= pipe insulation lineal thermal t
49、ransference, W/mKBtuin/Fhrft2,lp= pipe insulation thermal conductivity, W/mKBtuin/Fhrft2,rL= pipe insulation thermal resistivity, Km/WFhrft2,h2= surface areal heat transfer coefficient of insulationouter surface, W/m2K Btu in/F hr ft2,C335/C355M 103C = areal thermal conductance, W/m2K Btu in/Fhrft2,R = areal thermal resistance, Km2/WFhr
