ASTM E511-07
(Test Method)Standard Test Method for Measuring Heat Flux Using a Copper-Constantan Circular Foil, Heat-Flux Transducer
Standard Test Method for Measuring Heat Flux Using a Copper-Constantan Circular Foil, Heat-Flux Transducer
SCOPE
1.1 This test method describes the measurement of radiative heat flux using a transducer whose sensing element (1,2 ) is a thin circular metal foil. These sensors are often called Gardon Gauges.
1.2 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are provided for information only.
1.3 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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Designation: E511 − 07
StandardTest Method for
Measuring Heat Flux Using a Copper-Constantan Circular
1
Foil, Heat-Flux Transducer
This standard is issued under the fixed designation E511; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope under steady-state conditions. The center–perimeter tempera-
ture difference produces a thermoelectric potential, E, that will
1.1 Thistestmethoddescribesthemeasurementofradiative
2 varyinproportiontotheabsorbedheatflux, q'.Withprescribed
heat flux using a transducer whose sensing element (1, 2) is a
foildiameter,thickness,andmaterials,thepotential Eisalmost
thin circular metal foil. These sensors are often called Gardon
linearlyproportionaltotheaverageheatflux q'absorbedbythe
Gauges.
foil. This relationship is described by the following equation:
1.2 The values stated in SI units are to be regarded as the
E 5 Kq' (1)
standard. The values stated in parentheses are provided for
information only.
where:
1.3 This standard does not purport to address all of the K = a sensitivity constant determined experimentally.
safety concerns, if any, associated with its use. It is the
2.3 For nearly linear response, the heat sink and the center
responsibility of the user of this standard to establish appro-
wire of the transducer are made of high purity copper and the
priate safety and health practices and determine the applica-
foil of thermocouple grade Constantan. This combination of
bility of regulatory limitations prior to use.
materials produces a nearly linear output over a gauge tem-
perature range from –45 to 232°C (–50 to 450°F). The linear
2. Summary of Test Method
range results from the basically offsetting effects of
2.1 The purpose of this test method is to facilitate measure-
temperature-dependent changes in the thermal conductivity
ment of a radiant heat flux. Although the sensor will measure
and the Seebeck coefficient of the Constantan (3). All further
heat fluxes from mixed radiative – convective or pure convec-
discussion is based on the use of these two metals, since
tive sources, the uncertainty will increase as the convective
engineering practice has demonstrated they are commonly the
fraction of the total heat flux increases.
most useful.
2.2 The circular foil heat flux transducer generates a milli-
3. Description of the Instrument
Volt output in response to the rate of thermal energy absorbed
3.1 Fig. 1 is a sectional view of an example circular foil
(see Fig. 1). The perimeter of the circular metal foil sensing
heat-flux transducer. It consists of a circular Constantan foil
element is mounted in a metal heat sink, forming a reference
attached by a metallic bonding process to a heat sink of
thermocouple junction due to their different thermoelectric
oxygen-free high conductivity copper (OFHC), with copper
potentials. A differential thermocouple is created by a second
leads attached at the center of the circular foil and at any point
thermocouple junction formed at the center of the foil using a
ontheheat-sinkbody.Thetransducerimpedanceisusuallyless
fine wire of the same metal as the heat sink. When the sensing
than1V.Tominimizecurrentflow,thedataacquisitionsystem
element is exposed to a heat source, most of the heat energy
(DAS) should be a potentiometric system or have an input
absorbedatthesurfaceofthecircularfoilisconductedradially
impedance of at least 100 000 Ω.
to the heat sink. If the heat flux is uniform and heat transfer
down the center wire is neglected, a parabolic temperature
3.2 As noted in 2.3, an approximately linear output (versus
profile is established between the center and edge of the foil
heat flux) is produced when the body and center wire of the
transducer are constructed of copper and the circular foil is
constantan. Other metal combinations may be employed for
1
This test method is under the jurisdiction of ASTM Committee E21 on Space
use at higher temperatures, but most (4) are nonlinear.
Simulation andApplications of SpaceTechnology and is the direct responsibility of
3.3 Because the thermocouple junction at the edge of the
Subcommittee E21.08 on Thermal Protection.
Current edition approved Nov. 1, 2007. Published December 2007. Originally
foil is the reference for the center thermocouple, no cold
approved in 1973. Last previous edition approved in 2001 as E511–01. DOI:
junction compensation is required with this instrument. The
10.1520/E0511-07.
2
wire leads used to convey the signal from the transducer to the
The boldface numbers in parentheses refer to the list of references at the end of
this standard. readout device are normally made
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E511–01 Designation:E511–07
Standard Test Method for
Measuring Heat Flux Using a Copper-Constantan Circular
1
Foil, Heat-Flux Transducer
This standard is issued under the fixed designation E 511; 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
1.1 This test method describes the measurement of radiative or convective heat flux, or both,flux using a transducer whose
2
sensing element (1, 2) is a thin circular metal foil. While benchmark calibration standards exist for radiative environments, no
uniform agreement among practitioners or government entities exists for convective environments. is a thin circular metal foil.
These sensors are often called Gardon Gauges.
1.2 ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesstatedinparenthesesareprovidedforinformation
only.
1.3 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.
2. Summary of Test Method
2.1The purpose of this test method is to facilitate measurement of heat flux from radiant or convective sources, or from a
combination of the two.
2.2The circular foil heat flux transducer generates a millivolt output in response to the rate of thermal energy absorbed (see
2.1 The purpose of this test method is to facilitate measurement of a radiant heat flux. Although the sensor will measure heat
fluxes from mixed radiative – convective or pure convective sources, the uncertainty will increase as the convective fraction of
the total heat flux increases.
2.2 The circular foil heat flux transducer generates a milliVolt output in response to the rate of thermal energy absorbed (see
Fig. 1).The perimeter of the circular metal foil sensing element is mounted in a metal heat sink around its perimeter, sink, forming
a reference thermocouple junction due to their different thermoelectric potentials. A differential thermocouple is created by a
second thermocouple junction is formed at the center of the foil using a fine wire of the same metal as the heat sink. When the
sensing element is exposed to a heat source, most of the heat energy is absorbed at the surface of the circular foil andis conducted
radially to the heat sink.This establishes If the heat flux is uniform and heat transfer down the center wire is neglected, a parabolic
temperature gradient profile is established between the center and edge of the foil under steady-state conditions. The
center – perimeter temperature gradientdifference produces a thermoelectric potential, E, between the center wire and the heat sink
that will vary in proportion to the absorbed heat flux, q9.8. With prescribed foil diameter, thickness, and materials, the potential E
is almost linearly proportional to the average heat flux q98 absorbed by the foil. This relationship is described by the following
equation:
E5Kq9
E 5 Kq8 (1)
where:
K = a sensitivity constant determined experimentally.
2.3 For nearly linear response, the heat sink and the center wire of the transducer normally is are made of high purity copper
and the foil of thermocouple grade cConstantan. This combination of materials produces a nearly linear output over a gauge
temperature range from -45–45 to 232°C (-50(–50 to 450°F). The linear range results from the basically offsetting effects of
temperature-dependent changes in the thermal conductivity and the Seebeck coefficient of the cConstantan (3) . All further
discussionisbasedontheuseofthesetwometals,sinceengineeringpracticehasdemonstratedtheyarecommonlythemostuseful.
1
This test method is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection.
e1
Current edition approved Oct. 10, 2001. Published January 2002. Originally published as E511–73. Last previous edition E511–73 (1994) .
Current edition approved Nov. 1, 2007. Published December 2007. Originally approved in 1973. Last previous edition approved in 2001 as E 511 – 01.
2
The boldface numbers in parentheses refer to the list of references at the end of this test method.standard.
Copyright © ASTM International, 1
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