ASTM C1130-90(1995)e1
(Practice)Standard Practice for Calibrating Thin Heat Flux Transducers
Standard Practice for Calibrating Thin Heat Flux Transducers
SCOPE
1.1 This practice establishes an experimental procedure for determining the sensitivity of heat flux transducers (HFTs) that are relatively thin. The term sensitivity in this practice refers to the ratio of HFT electrical output to heat flux through the HFT.
1.1.1 For the purpose of this standard, the thickness of the HFT shall be less than 15 % of the narrowest planar dimension of the HFT.
1.2 This practice discusses two methods for determining HFT sensitivity. The first method is the calibration of the HFT in unperturbed heat flow normal to the surface of the HFT, while the second method is the sensitivity of the HFT in actual use, or the HFT conversion factor.
1.3 This practice should be used in conjunction with Practice C1041 when measuring in-situ heat flux and temperature on industrial insulation systems, and with Practice C1046 when performing in-situ measurements of heat flux on opaque building components.
1.4 This practice is not intended to determine the sensitivity of HFTs that are components of heat flow meter apparatus, as in Test Method C518. Refer to Practice C1132 for this purpose.
1.5 The following safety caveat pertains only to the Specimen Preparation and Procedure portions, Sections and , of this practice: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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e1
Designation: C 1130 – 90 (Reapproved 1995)
Standard Practice for
Calibrating Thin Heat Flux Transducers
This standard is issued under the fixed designation C 1130; 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.
e NOTE—Keywords were added editorially in October 1995.
1. Scope the Guarded-Hot-Plate Apparatus
C 236 Test Method for Steady-State Thermal Performance
1.1 This practice establishes an experimental procedure for
of Building Assemblies by Means of a Guarded Hot Box
determining the sensitivity of heat flux transducers (HFTs) that
C 335 Test Method for Steady-State Heat Transfer Proper-
are relatively thin. The term sensitivity in this practice refers to
ties of Horizontal Pipe Insulation
the ratio of HFT electrical output to heat flux through the HFT.
C 518 Test Method for Steady-State Heat Flux Measure-
1.1.1 For the purpose of this standard, the thickness of the
ments and Thermal Transmission Properties by Means of
HFT shall be less than 15 % of the narrowest planar dimension
the Heat Flow Meter Apparatus
of the HFT.
C 976 Test Method for Thermal Performance of Building
1.2 This practice discusses two methods for determining
Assemblies by Means of a Calibrated Hot Box
HFT sensitivity. The first method is the calibration of the HFT
C 1041 Practice for In-Situ Measurements of Heat Flux in
in unperturbed heat flow normal to the surface of the HFT,
Industrial Thermal Insulation Using Heat Flux Transduc-
while the second method is the sensitivity of the HFT in actual
ers
use, or the HFT conversion factor.
C 1044 Practice for Using the Guarded-Hot-Plate Apparatus
1.3 This practice should be used in conjunction with Prac-
in the One-Sided Mode to Measure Steady-State Heat Flux
tice C 1041 when measuring in-situ heat flux and temperature
and Thermal Transmission Properties
on industrial insulation systems, and with Practice C 1046
C 1046 Practice for In-Situ Measurement of Heat Flux and
when performing in-situ measurements of heat flux on opaque
Temperature on Building Envelope Components
building components.
C 1114 Test Method for Steady-State Thermal Transmission
1.4 This practice is not intended to determine the sensitivity
Properties by Means of the Thin-Heater Apparatus
of HFTs that are components of heat flow meter apparatus, as
C 1132 Practice for Calibration of the Heat Flow Meter
in Test Method C 518. Refer to Practice C 1132 for this
Apparatus
purpose.
1.5 The following safety caveat pertains only to the Speci-
3. Terminology
men Preparation and Procedure portions, Sections 5 and 6, of
3.1 Definitions—For definitions of terms relating to thermal
this practice: This standard does not purport to address all of
insulating materials, see Definitions C 168.
the safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 heat flux transducer—a device containing a thermo-
priate safety and health practices and determine the applica-
pile (or equivalent) that produces an output which is a function
bility of regulatory limitations prior to use.
of the heat flux passing through the HFT.
2. Referenced Documents 3.2.2 sensitivity—the ratio of the electrical output of the
heat flux transducer to the heat flux passing through the HFT.
2.1 ASTM Standards:
The sensitivity of the HFT will be a function of the HFT
C 168 Terminology Relating to Thermal Insulating Materi-
2 temperature, the HFT construction, its curvature, and the
als
method with which it is applied to the building component.
C 177 Test Method for Steady-State Heat Flux Measure-
3.2.3 heat flux transducer calibration factor—the sensitiv-
ments and Thermal Transmission Properties by Means of
ity of the heat flux transducer when measured in an undisturbed
one-dimensional temperature field.
This practice is under the jurisdiction of ASTM Committee C-16 on Thermal
3.2.4 heat flux transducer conversion factor—the sensitivity
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
of the heat flux transducer for the thermal conditions surround-
Measurement.
ing the HFT in actual use.
Current edition approved June 29, 1990. Published August 1990. Originally
3.2.4.1 The relationship between the heat flux transducer
published as C 1130 – 89. Last previous edition C 1130 – 89.
Annual Book of ASTM Standards, Vol 04.06.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C 1130
calibration and conversion factors is indicative of the magni- 4.7 The method of HFT application must be adequately
tude of the heat flux distortion created by the application of the simulated or duplicated when experimentally determining the
HFT. HFT sensitivity. The two most widely used application tech-
3.2.5 temperature field—a set of temperatures, where each niques are to surface-mount the HFT or to embed the HFT in
temperature is associated with a point or small domain of space the insulation system.
in a region of interest. An example is the distribution of
5. Specimen Preparation
temperatures within a slab of insulation.
5.1 Preparation of the HFT depends on which type of
3.2.6 test stack—a layer or a series of layers of material put
sensitivity is desired and the method of HFT application to be
together to comprise a test sample (for example, a roof system
employed.
containing a membrane, an insulation, and a roof deck).
5.1.1 Three separate cases are discussed: the determination
3.3 Symbols:
of the calibration factor and the measurement of the conversion
factor for embedded and surface-mounted HFTs.
2 2
q 5 heat flux, W/m [Btu/h·ft ].
5.2 The HFT for which sensitivity is determined will
V 5 measured output voltage of the HFT, V .
measure the heat flux at the position of the HFT in the test
2 2
S 5 sensitivity of the HFT, V/(W/m ) [V/(Btu/hr·ft )].
stack. It is recommended that the HFT be installed near the
metering side of the test instrument and in a relatively thin
4. Significance and Use
stack assembly to reduce the impact of edge effects. The
4.1 The use of heat flux transducers on industrial equipment
thickness and thermal resistance of the test stack should be
or building envelope components provides the user with a
selected after considering its impact on the accuracy of the
relatively simple means for performing in-situ heat flux mea-
chosen test method.
surements. Accurate translation of the heat flux transducer
5.3 Calibration factor—The HFT shall be embedded in a
output requires a complete understanding of the factors affect-
stack of materials and surrounded with a framing material or
ing its output, and a standardized method for determining the
mask. Guarded-hot-plate and heat flow meter apparatuses (Test
HFT sensitivity for the application of interest.
Method C 177 and C 518, respectively) have been successfully
4.2 The placement of an HFT in a temperature field (see
used for this purpose.
3.2.5) will probably disturb that field. If a disturbance in the
5.3.1 The sample stack used to determine the calibration
temperature field occurs when the HFT is applied, the user
factor of HFTs shall consist of a sandwich of the HFT/masking
must account for that disturbance when determining the
layer between two layers of a compressible homogeneous
sensitivity of an HFT.
material, such as high-density fiberglass insulation board, to
4.3 There are several methods for determining the sensitiv-
assure good thermal contact between the plates of the tester and
ity of HFTs (see 6.1). The selection of the best procedure will
the HFT/masking layer. The use of a thermally conductive gel
depend on the required accuracy and the physical limitations of
is another technique to improve good thermal contact.
available equipment.
5.3.2 The mask used in determining the HFT calibration
4.4 The presence of a heat flux transducer is likely to alter
factor must have the same thickness and thermal resistance as
the heat flux that is being measured. This disturbance is
the HFT. The matching of the mask and HFT is sensitive to the
difficult to predict without sufficient knowledge of the con-
HFT size and on whether the HFT incorporates an intrinsic
struction of the HFT and the thermal conductivities of both the
mask surrounding its active sensing area. An effective masking
HFT components and its surroundings. With such knowledge,
technique that has been employed for small sensors is to utilize
analytical (1, 2) and numerical (3, 4, 5) methods have been
other identical sensors as a mask.
used to account for the disturbance in heat flux caused by the
5.4 Conversion factor, embedded—The HFT shall be
presence of an HFT.
placed, in a fashion identical to its end use application, in a
4.5 If an HFT calibration factor is sought, the user of this
stack of materials duplicating the building construction to be
standard must assure that parallel heat flow, normal to the HFT,
evaluated. The instruments listed in 5.3 along with the thin-
is achieved. If the user wishes to obtain a conversion factor,
heater apparatus (see Test Method C 1114) have been used for
then the user must account for the end-use conditions of the
this analysis.
HFT, either by using an acceptable and verifiable mathematical
5.5 Conversion factor, surface mounted—The HFT shall be
technique to correct the calibration factor, or by performing a
applied in a manner identical to that of actual use to a
series of experiments that adequately simulates the conditions
homogeneous test panel or pipe insulation of similar thermal
of use to obtain the conversion factor empirically (6, 7, 8).
resistance, surface-layer thermal conductance, and orientation.
4.6 This practice describes techniques to establish uniform
Pipe tester (Test Method C 335), guarded-hot-box (Test
heat flow normal to the heat flux transducer for the determi-
Method C 236), and calibrated-hot-box (Test Method C 976)
nation of the HFT calibration factor, or how to establish
apparatuses have been used to perform
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