ASTM C1667-07
(Test Method)Standard Test Method for Using Heat Flow Meter Apparatus to Measure the Center-of-Panel Thermal Resistivity of Vacuum Panels
Standard Test Method for Using Heat Flow Meter Apparatus to Measure the Center-of-Panel Thermal Resistivity of Vacuum Panels
SIGNIFICANCE AND USE
Heat flow meter apparatus are being used to measure the center-of-panel portion of a vacuum insulation panel, which typically has a very high value of thermal resistivity [that is, equal to or greater than 90 m-K/W (12.5 h-ft2-°F/Btu-in.)]. As described in Specification C 1484, the center-of-panel thermal resistivity is used, along with the panel geometry and barrier material thermal conductivity, to determine the effective thermal resistance of the evacuated panel.
Using a heat flow meter apparatus to measure the thermal resistivity of non-homogenous and high thermal resistance specimens is a non-standard application of the equipment, and shall only be performed by qualified personnel with understanding of heat transfer and error propagation. Familiarity with the configuration of both the apparatus and the vacuum panel is necessary.
The center-of-panel thermal transmission properties of evacuated panels vary due to the composition of the materials of construction, mean temperature and temperature difference, and the prior history. The selection of representative values for the thermal transmission properties of an evacuated panel for a particular application must be based on a consideration of these factors and will not apply necessarily without modification to all service conditions.
SCOPE
1.1 This test method covers the measurement of steady-state thermal transmission through the center of a flat rectangular vacuum insulation panel using a heat flow meter apparatus.
1.2 Total heat transfer through the non-homogenous geometry of a vacuum insulation panel requires the determination of several factors, as discussed in Specification C 1484. One of those factors is the center-of-panel thermal resistivity. The center-of-panel thermal resistivity is an approximation of the thermal resistivity of the core evacuated region.
1.3 This test method is based upon the technology of Test Method C 518 but includes modifications for vacuum panel applications as outlined in this test method.
1.4 This test method shall be used in conjunction with Practice C 1045 and Practice C 1058.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. Either SI or inch-pound units are acceptable in the report, unless otherwise specified.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
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Designation:C1667–07
Standard Test Method for
Using Heat Flow Meter Apparatus to Measure the Center-of-
Panel Thermal Resistivity of Vacuum Panels
This standard is issued under the fixed designation C 1667; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope C 1045 Practice for Calculating Thermal Transmission
Properties Under Steady-State Conditions
1.1 Thistestmethodcoversthemeasurementofsteady-state
C 1058 Practice for Selecting Temperatures for Evaluating
thermal transmission through the center of a flat rectangular
and Reporting Thermal Properties of Thermal Insulation
vacuum insulation panel using a heat flow meter apparatus.
C 1484 Specification for Vacuum Insulation Panels
1.2 Total heat transfer through the non-homogenous geom-
etry of a vacuum insulation panel requires the determination of
3. Terminology
several factors, as discussed in Specification C 1484. One of
3.1 Definitions—Terminology C 168 applies to terms used
those factors is the center-of-panel thermal resistivity. The
in this specification.
center-of-panel thermal resistivity is an approximation of the
3.2 Definitions of Terms Specific to This Standard:
thermal resistivity of the core evacuated region.
3.2.1 center-of-panel—the location at the center of the
1.3 This test method is based upon the technology of Test
largest planar surface of the panel, equidistant from each pair
Method C 518 but includes modifications for vacuum panel
2 of opposite edges of that surface.
applications as outlined in this test method.
3.2.2 center-of-panel apparent thermal resistivity—the ther-
1.4 This test method shall be used in conjunction with
mal performance of vacuum panels includes an edge effect due
Practice C 1045 and Practice C 1058.
to heat flow through the barrier material and this shunting of
1.5 The values stated in SI units are to be regarded as the
heat around the evacuated volume of the panel becomes more
standard. The values given in parentheses are for information
prevalentwithgreaterbarrierthermalconductivity,asshownin
only. Either SI or inch-pound units are acceptable in the report,
Fig. 1. For panels larger than a minimum size (as described in
unless otherwise specified.
AnnexA1), the center-of-panel apparent thermal resistivity is a
1.6 This standard does not purport to address all of the
close approximation of the intrinsic core thermal resistivity of
safety concerns, if any, associated with its use. It is the
the vacuum insulation panel. The effective thermal perfor-
responsibility of the user of this standard to establish appro-
manceofapanelwillvarywiththesizeandshapeofthepanel.
priate safety and health practices and determine the applica-
3.2.2.1 Discussion—Thermal resistivity, the reciprocal of
bility of regulatory limitations prior to use.
apparent thermal conductivity, is used when discussing the
2. Referenced Documents center-of-panel thermal behavior.
3.2.3 core—the material placed within the evacuated vol-
2.1 ASTM Standards:
ume of a vacuum insulation panel. This material may perform
C 168 Terminology Relating to Thermal Insulation
any or all of the following functions: prevent panel collapse
C 518 Test Method for Steady-State Thermal Transmission
due to atmospheric pressure, reduce radiation heat transfer, and
Properties by Means of the Heat Flow Meter Apparatus
reduce gas-phase conduction. The apparent thermal conductiv-
C 740 Practice for Evacuated Reflective Insulation In Cryo-
ity of the core, or l , is defined as the apparent thermal
core
genic Service
conductivity of the core material under the same vacuum that
would occur within a panel, but without the barrier material.
This is the apparent thermal conductivity that would be
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal measured in a vacuum chamber without the barrier material.
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
3.2.4 effective panel thermal resistance (effective panel
Measurement.
R-value)—this value reflects the total panel resistance to heat
Current edition approved Sept. 1, 2007. Published September 2007.
flow, considering heat flow through the evacuated region and
AllreferencestoparticularsectionsofTestMethodC 518withinthisdocument
refer to the 2004 edition of Test Method C 518.
through the barrier material. Depending on the thermal con-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ductivity of the barrier material and the size of the panel, the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
effective thermal resistance may be significantly less than the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. product of the center-of-panel apparent thermal resistivity and
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
C1667–07
FIG. 1 Side View of a Vacuum Insulation Panel Showing Edge Heat Flow and the Center-of-Panel Region
the panel thickness. The effective thermal resistance is based L = thickness of a single layer of the calibra-
calibration standard
on the edge-to-edge area covered by the vacuum insulation tion standard material, m
panel, that is, the entire panel. The effective thermal resistance L = target total thickness of the calibra-
calibration standard, target
will also vary with the panel mean temperature. tion standard material, m
3.2.4.1 Discussion—Thermal resistance, the reciprocal of q = heat flux through the panel, W/m
thermal conductance, is used when discussing the effective Q = heat flow through the barrier material, W
barrier
thermal performance of the panel. This value includes the Q = estimated heat flow at the transducer (as
center-of-panel
effect of the actual panel dimensions, including the panel calculated by the model), W
thickness. Q = heat flow through the core region, W
core
3.2.5 evacuated or vacuum insulations—insulation systems R = thermalresistivityofthecalibrationstan-
calibration standard
whose gas phase thermal conductivity portion of the overall dard, m-K/W
apparent thermal conductivity has been significantly reduced R = center of panel thermal resistivity, m-K/W
center-of-panel
by reduction of the internal gas pressure. The level of vacuum S = calibration factor, (W/m )/V
willdependonpropertiesofthecompositepanelmaterials,and T = specimen cold surface temperature, K
c
the desired effective panel thermal resistance. T = specimen hot surface temperature, K
h
3.2.6 panel barrier—the material that envelops the evacu- t = thickness of the barrier material, m
barrier
atedvolumeandisusedtoseparatetheevacuatedvolumefrom W , W = panel width, panel length, m
1 2
the environment and to provide a long term barrier to gas and u = combined standard uncertainty
c
vapor diffusion. u = uncertainty component, for example, standard uncer-
n
3.2.7 seal—any joint between two pieces of barrier mate- tainty for the measurement
rial. Z = an approximate estimate of the ratio of the heat flow
edge
3.3 Symbols and Units: through the barrier material to the heat flow through the core
A = area of the barrier perpendicular to the largest material, dimensionless
barrier
panel faces, m l = thermal conductivity of the barrier material,
barrier
A = area of the largest panel face covering the core W/m-K
core
material, m l = apparent thermal conductivity of the core region,
core
C = calibration standard conductance, W/m -K W/m-K
E = heat flux transducer output, V
4. Summary of Test Method
L = panel thickness, m
panel
4.1 This test method describes a modified application of
Test Method C 518 to evacuated panels. These panels fall
outside the scope of Test Method C 518, both in their non-
For further discussion on heat flow mechanisms in evacuated insulations, see
Practice C 740 on Evacuated Reflective Insulation in Cryogenic Service. homogeneity and in the current lack of specimens having an
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
C1667–07
accepted reference value that are of similar size and have the 7.4.1 Preferably, specimens shall be of such size as to fully
necessary thermal characteristics. Therefore, modifications are cover the plate assembly surfaces, with an allowance of up to
necessaryintheareasofapparatuscalibration,plateseparation, 6 mm on each side to allow room for panel seals.
test procedures, precision and bias, and reporting. 7.4.2 If the width or length, or both, of the specimen are
smaller than the apparatus compartment, surround the speci-
NOTE 1—Primary calibration standards, using vacuum panels, have not
men with high thermal resistance insulation. This surrounding
been prepared for this class of products due to uncertainties about their
material will reduce edge heat transfer and prevent air circu-
long-term stability characteristics.
lation around the specimen.
7.5 For panels with smooth parallel surfaces, the specimen
5. Significance and Use
thickness is represented by the plate separation.
5.1 Heatflowmeterapparatusarebeingusedtomeasurethe
7.6 For panels with irregular surfaces, to insure thermal
center-of-panel portion of a vacuum insulation panel, which
contact with the apparatus surfaces, it is necessary to:
typically has a very high value of thermal resistivity [that is,
7.6.1 Measure the panel thickness with an accuracy of
equal to or greater than 90 m-K/W (12.5 h-ft -°F/Btu-in.)]. As
60.05 mm (0.002 in.) in at least five locations distributed over
described in Specification C 1484, the center-of-panel thermal
the surface of the panel and use the average of the local values.
resistivity is used, along with the panel geometry and barrier
Care shall be taken so that the contact between the caliper jaws
material thermal conductivity, to determine the effective ther-
or the length meter’s pressure foot does not damage the
mal resistance of the evacuated panel.
specimen surface.
5.2 Using a heat flow meter apparatus to measure the
7.6.2 Record the output of one thermocouple placed on the
thermal resistivity of non-homogenous and high thermal resis-
center of the top and one thermocouple placed on the center of
tance specimens is a non-standard application of the equip-
the bottom of the panel. The temperatures recorded by the
ment, and shall only be performed by qualified personnel with
thermocouples, not the hot and cold plate temperatures, shall
understanding of heat transfer and error propagation. Familiar-
be used to calculate the center-of-panel apparent thermal
itywiththeconfigurationofboththeapparatusandthevacuum
resistivity.
panel is necessary.
7.6.3 Place one sheet (approximately 3 mm thick) of an
5.3 The center-of-panel thermal transmission properties of
elastomeric or soft foam rubber between each side of the panel
evacuated panels vary due to the composition of the materials
and the corresponding apparatus plate. This sheet will improve
of construction, mean temperature and temperature difference,
contact between the controlled temperature plates and prevent
and the prior history. The selection of representative values for
air circulation between the panel and the plates.
the thermal transmission properties of an evacuated panel for a
particularapplicationmustbebasedonaconsiderationofthese
8. Calibration
factors and will not apply necessarily without modification to
8.1 The apparatus shall be calibrated according to Test
all service conditions.
Method C 518 sections 6.1 to 6.5.
8.2 Specimens having an accepted reference value with
6. Apparatus
physical and thermal characteristics similar to vacuum panels
6.1 FollowTestMethodC 518,Section5exceptuseSection
are not yet available. The linearity of the heat flux transducers
8 of this test method for calibration.
at very low levels of heat flux must be verified using another
method. The apparatus calibration must include the addition of
7. Specimen Preparation
at least one of the modified calibration procedures described in
8.5 and 8.6, that is Modified Calibration ProcedureAor B.As
7.1 Vacuum insulation panels are typically rigid and the
described in 8.7, the two modified procedures can be combined
shape cannot be modified for testing purposes. However, to
if necessary to meet uncertainty goals. Although each method
obtain representative thermal values for the panel, the two
magnifies an element of experimental error (as discussed
primary surfaces must be parallel and have limited surface
below), it is necessary to augment the standard Test Method
irregularities.
C 518 calibration for this particular application.
7.2 If none of the standard product sizes are appropriate for
8.3 It is not intended that the heat flow meter apparatus
the heat flow meter apparatus used in this test, then represen-
calibration be altered based on the results of these supplemen-
tative test specimens must be produced so that they accurately
tary procedures. Rather the results will be used by qualified
represent both the same average performance as the production
personnel (as described in 5.2) to determine whether a particu-
product and the same typical product variability.
lar heat flow meter apparatus will give meaningful results for
7.3 The specimens shall be of the same thickness as the
a vacuum panel application, and if so, to provide guidance on
average thickness to be applied in use.
interpreting and applying the Test Method C 518 test results.
7.4 The minimum panel size for this test is determined by
NOTE 2—Just as with the standard calibration technique, the supple-
the size of the heat flux transducer in the heat flow meter
mentary calibration need not be repeated for every test if the equipment
apparatus, the overall maximum specimen size limit for the
has been stable over a significant period of time. See Test Method C 518
apparatus, the thermal conductivity of the barrier, the thickness
section 4.5.1.
of the barrier, and the thermal conductivity of the core.Annex
NOTE 3—The heat flow meter apparatus may take a long time to reach
A1 contains a procedure to estimate the minimum acceptable
a true steady-state condition for low conductance specimens, as described
panel size. in Test Method C 518 section 7.7.3.
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