1、Designation: C 1667 07Standard Test Method forUsing Heat Flow Meter Apparatus to Measure the Center-of-Panel Thermal Resistivity of Vacuum Panels1This standard is issued under the fixed designation C 1667; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, the year 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 test method covers the measurement of steady-statethermal transmission throug
3、h the center of a flat rectangularvacuum insulation panel using a heat flow meter apparatus.1.2 Total heat transfer through the non-homogenous geom-etry of a vacuum insulation panel requires the determination ofseveral factors, as discussed in Specification C 1484. One ofthose factors is the center-
4、of-panel thermal resistivity. Thecenter-of-panel thermal resistivity is an approximation of thethermal resistivity of the core evacuated region.1.3 This test method is based upon the technology of TestMethod C 518 but includes modifications for vacuum panelapplications as outlined in this test metho
5、d.21.4 This test method shall be used in conjunction withPractice C 1045 and Practice C 1058.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly. Either SI or inch-pound units are acceptable in the report,unless otherwise speci
6、fied.1.6 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 determine the applica-bility of regulatory limitations prior to use.2. Referen
7、ced Documents2.1 ASTM Standards:3C 168 Terminology Relating to Thermal InsulationC 518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusC 740 Practice for Evacuated Reflective Insulation In Cryo-genic ServiceC 1045 Practice for Calculating Thermal
8、TransmissionProperties Under Steady-State ConditionsC 1058 Practice for Selecting Temperatures for Evaluatingand Reporting Thermal Properties of Thermal InsulationC 1484 Specification for Vacuum Insulation Panels3. Terminology3.1 DefinitionsTerminology C 168 applies to terms usedin this specificatio
9、n.3.2 Definitions of Terms Specific to This Standard:3.2.1 center-of-panelthe location at the center of thelargest planar surface of the panel, equidistant from each pairof opposite edges of that surface.3.2.2 center-of-panel apparent thermal resistivitythe ther-mal performance of vacuum panels incl
10、udes an edge effect dueto heat flow through the barrier material and this shunting ofheat around the evacuated volume of the panel becomes moreprevalent with greater barrier thermal conductivity, as shown inFig. 1. For panels larger than a minimum size (as described inAnnexA1), the center-of-panel a
11、pparent thermal resistivity is aclose approximation of the intrinsic core thermal resistivity ofthe vacuum insulation panel. The effective thermal perfor-mance of a panel will vary with the size and shape of the panel.3.2.2.1 DiscussionThermal resistivity, the reciprocal ofapparent thermal conductiv
12、ity, is used when discussing thecenter-of-panel thermal behavior.3.2.3 corethe material placed within the evacuated vol-ume of a vacuum insulation panel. This material may performany or all of the following functions: prevent panel collapsedue to atmospheric pressure, reduce radiation heat transfer,
13、 andreduce gas-phase conduction. The apparent thermal conductiv-ity of the core, or lcore, is defined as the apparent thermalconductivity of the core material under the same vacuum thatwould occur within a panel, but without the barrier material.This is the apparent thermal conductivity that would b
14、emeasured in a vacuum chamber without the barrier material.3.2.4 effective panel thermal resistance (effective panelR-value)this value reflects the total panel resistance to heatflow, considering heat flow through the evacuated region andthrough the barrier material. Depending on the thermal con-duc
15、tivity of the barrier material and the size of the panel, theeffective thermal resistance may be significantly less than theproduct of the center-of-panel apparent thermal resistivity and1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsib
16、ility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved Sept. 1, 2007. Published September 2007.2All references to particular sections of Test Method C 518 within this documentrefer to the 2004 edition of Test Method C 518.3For referenced ASTM standards, visit the ASTM website, w
17、ww.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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the
18、 panel thickness. The effective thermal resistance is basedon the edge-to-edge area covered by the vacuum insulationpanel, that is, the entire panel. The effective thermal resistancewill also vary with the panel mean temperature.3.2.4.1 DiscussionThermal resistance, the reciprocal ofthermal conducta
19、nce, is used when discussing the effectivethermal performance of the panel. This value includes theeffect of the actual panel dimensions, including the panelthickness.3.2.5 evacuated or vacuum insulationsinsulation systemswhose gas phase thermal conductivity portion of the overallapparent thermal co
20、nductivity has been significantly reducedby reduction of the internal gas pressure. The level of vacuumwill depend on properties of the composite panel materials, andthe desired effective panel thermal resistance.43.2.6 panel barrierthe material that envelops the evacu-ated volume and is used to sep
21、arate the evacuated volume fromthe environment and to provide a long term barrier to gas andvapor diffusion.3.2.7 sealany joint between two pieces of barrier mate-rial.3.3 Symbols and Units:Abarrier= area of the barrier perpendicular to the largestpanel faces, m2Acore= area of the largest panel face
22、 covering the corematerial, m2C = calibration standard conductance, W/m2-KE = heat flux transducer output, VLpanel= panel thickness, mLcalibration standard= thickness of a single layer of the calibra-tion standard material, mLcalibration standard, target= target total thickness of the calibra-tion s
23、tandard material, mq = heat flux through the panel, W/m2Qbarrier= heat flow through the barrier material, WQcenter-of-panel= estimated heat flow at the transducer (ascalculated by the model), WQcore= heat flow through the core region, WRcalibration standard= thermal resistivity of the calibration st
24、an-dard, m-K/WRcenter-of-panel= center of panel thermal resistivity, m-K/WS = calibration factor, (W/m2)/VTc= specimen cold surface temperature, KTh= specimen hot surface temperature, Ktbarrier= thickness of the barrier material, mW1, W2= panel width, panel length, muc= combined standard uncertainty
25、un= uncertainty component, for example, standard uncer-tainty for the measurementZedge= an approximate estimate of the ratio of the heat flowthrough the barrier material to the heat flow through the corematerial, dimensionlesslbarrier= thermal conductivity of the barrier material,W/m-Klcore= apparen
26、t thermal conductivity of the core region,W/m-K4. Summary of Test Method4.1 This test method describes a modified application ofTest Method C 518 to evacuated panels. These panels falloutside the scope of Test Method C 518, both in their non-homogeneity and in the current lack of specimens having an
27、4For further discussion on heat flow mechanisms in evacuated insulations, seePractice C 740 on Evacuated Reflective Insulation in Cryogenic Service.FIG. 1 Side View of a Vacuum Insulation Panel Showing Edge Heat Flow and the Center-of-Panel RegionC1667072accepted reference value that are of similar
28、size and have thenecessary thermal characteristics. Therefore, modifications arenecessary in the areas of apparatus calibration, plate separation,test procedures, precision and bias, and reporting.NOTE 1Primary calibration standards, using vacuum panels, have notbeen prepared for this class of produ
29、cts due to uncertainties about theirlong-term stability characteristics.5. Significance and Use5.1 Heat flow meter apparatus are being used to measure thecenter-of-panel portion of a vacuum insulation panel, whichtypically has a very high value of thermal resistivity that is,equal to or greater than
30、 90 m-K/W (12.5 h-ft2-F/Btu-in.). Asdescribed in Specification C 1484, the center-of-panel thermalresistivity is used, along with the panel geometry and barriermaterial thermal conductivity, to determine the effective ther-mal resistance of the evacuated panel.5.2 Using a heat flow meter apparatus t
31、o measure thethermal resistivity of non-homogenous and high thermal resis-tance specimens is a non-standard application of the equip-ment, and shall only be performed by qualified personnel withunderstanding of heat transfer and error propagation. Familiar-ity with the configuration of both the appa
32、ratus and the vacuumpanel is necessary.5.3 The center-of-panel thermal transmission properties ofevacuated panels vary due to the composition of the materialsof construction, mean temperature and temperature difference,and the prior history. The selection of representative values forthe thermal tran
33、smission properties of an evacuated panel for aparticular application must be based on a consideration of thesefactors and will not apply necessarily without modification toall service conditions.6. Apparatus6.1 Follow Test Method C 518, Section 5 except use Section8 of this test method for calibrat
34、ion.7. Specimen Preparation7.1 Vacuum insulation panels are typically rigid and theshape cannot be modified for testing purposes. However, toobtain representative thermal values for the panel, the twoprimary surfaces must be parallel and have limited surfaceirregularities.7.2 If none of the standard
35、 product sizes are appropriate forthe heat flow meter apparatus used in this test, then represen-tative test specimens must be produced so that they accuratelyrepresent both the same average performance as the productionproduct and the same typical product variability.7.3 The specimens shall be of t
36、he same thickness as theaverage thickness to be applied in use.7.4 The minimum panel size for this test is determined bythe size of the heat flux transducer in the heat flow meterapparatus, the overall maximum specimen size limit for theapparatus, the thermal conductivity of the barrier, the thickne
37、ssof the barrier, and the thermal conductivity of the core. AnnexA1 contains a procedure to estimate the minimum acceptablepanel size.7.4.1 Preferably, specimens shall be of such size as to fullycover the plate assembly surfaces, with an allowance of up to6 mm on each side to allow room for panel se
38、als.7.4.2 If the width or length, or both, of the specimen aresmaller than the apparatus compartment, surround the speci-men with high thermal resistance insulation. This surroundingmaterial will reduce edge heat transfer and prevent air circu-lation around the specimen.7.5 For panels with smooth pa
39、rallel surfaces, the specimenthickness is represented by the plate separation.7.6 For panels with irregular surfaces, to insure thermalcontact with the apparatus surfaces, it is necessary to:7.6.1 Measure the panel thickness with an accuracy of60.05 mm (0.002 in.) in at least five locations distribu
40、ted overthe surface of the panel and use the average of the local values.Care shall be taken so that the contact between the caliper jawsor the length meters pressure foot does not damage thespecimen surface.7.6.2 Record the output of one thermocouple placed on thecenter of the top and one thermocou
41、ple placed on the center ofthe bottom of the panel. The temperatures recorded by thethermocouples, not the hot and cold plate temperatures, shallbe used to calculate the center-of-panel apparent thermalresistivity.7.6.3 Place one sheet (approximately 3 mm thick) of anelastomeric or soft foam rubber
42、between each side of the paneland the corresponding apparatus plate. This sheet will improvecontact between the controlled temperature plates and preventair circulation between the panel and the plates.8. Calibration8.1 The apparatus shall be calibrated according to TestMethod C 518 sections 6.1 to
43、6.5.8.2 Specimens having an accepted reference value withphysical and thermal characteristics similar to vacuum panelsare not yet available. The linearity of the heat flux transducersat very low levels of heat flux must be verified using anothermethod. The apparatus calibration must include the addi
44、tion ofat least one of the modified calibration procedures described in8.5 and 8.6, that is Modified Calibration Procedure A or B. Asdescribed in 8.7, the two modified procedures can be combinedif necessary to meet uncertainty goals. Although each methodmagnifies an element of experimental error (as
45、 discussedbelow), it is necessary to augment the standard Test MethodC 518 calibration for this particular application.8.3 It is not intended that the heat flow meter apparatuscalibration be altered based on the results of these supplemen-tary procedures. Rather the results will be used by qualified
46、personnel (as described in 5.2) to determine whether a particu-lar heat flow meter apparatus will give meaningful results fora vacuum panel application, and if so, to provide guidance oninterpreting and applying the Test Method C 518 test results.NOTE 2Just as with the standard calibration technique
47、, the supple-mentary calibration need not be repeated for every test if the equipmenthas been stable over a significant period of time. See Test Method C 518section 4.5.1.NOTE 3The heat flow meter apparatus may take a long time to reacha true steady-state condition for low conductance specimens, as
48、describedin Test Method C 518 section 7.7.3.C16670738.4 In order to evaluate the linearity of the heat fluxtransducers at the reduced levels of heat flux that will occurwith the vacuum insulation panels, a target heat flux iscalculated from Eq 1, using the best information availableabout the center-
49、of-panel thermal resistivity, the panel thick-ness, and the temperature difference of interest.qtarget5Th Tc!Rcenter of panel, estimated3 Lpanel(1)8.5 Modified Calibration Procedure AMake a series oftest measurements using multiple thicknesses of the calibrationstandard, with a radiation-blocking septum between the layers.Calculate a target thickness for the heat flux level of interestusing Eq 2, recognizing that the actual thickness will be aneven multiple of the thickness of a single layer or the sum ofthe available calibration standard thicknesses.Lcalibration st
