ASTM E457-96(2002)
(Test Method)Standard Test Method for Measuring Heat-Transfer Rate Using a Thermal Capacitance (Slug) Calorimeter
Standard Test Method for Measuring Heat-Transfer Rate Using a Thermal Capacitance (Slug) Calorimeter
SIGNIFICANCE AND USE
The purpose of this test method is to measure the rate of thermal energy per unit area transferred into a known piece of material (slug) for purposes of calibrating the thermal environment into which test specimens are placed for evaluation. The calorimeter and holder size and shape should be identical to that of the test specimen. In this manner, the measured heat transfer rate to the calorimeter can be related to that experienced by the test specimen.
The slug calorimeter is one of many calorimeter concepts used to measure heat transfer rate. This type of calorimeter is simple to fabricate, inexpensive, and readily installed since it is not water-cooled. The primary disadvantages are its short lifetime and relatively long cool-down time after exposure to the thermal environment. In measuring the heat transfer rate to the calorimeter, accurate measurement of the rate of rise in back-face temperature is imperative.
In the evaluation of high-temperature materials, slug calorimeters are used to measure the heat transfer rate on various parts of the instrumented models, since heat transfer rate is one of the important parameters in evaluating the performance of ablative materials.
Regardless of the source of thermal energy to the calorimeter (radiative, convective, or a combination thereof) the measurement is averaged over the calorimeter surface. If a significant percentage of the total thermal energy is radiative, consideration should be given to the emissivity of the slug surface. If non-uniformities exist in the input energy, the heat transfer rate calorimeter would tend to average these variations; therefore, the size of the sensing element (that is, the slug) should be limited to small diameters in order to measure local heat transfer rate values. Where large ablative samples are to be tested, it is recommended that a number of calorimeters be incorporated in the body of the test specimen such that a heat transfer rate distribution across the heated surface...
SCOPE
1.1 This test method describes the measurement of heat transfer rate using a thermal capacitance-type calorimeter which assumes one-dimensional heat conduction into a cylindrical piece of material (slug) with known physical properties.
1.2 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.
1.3 The values stated in SI units are to be regarded as the standard.
Note 1—For information see Test Methods E 285, E 422, E 458, E 459, and E 511.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E457–96 (Reapproved 2002)
Standard Test Method for
Measuring Heat-Transfer Rate Using a Thermal Capacitance
(Slug) Calorimeter
This standard is issued under the fixed designation E457; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope E459 TestMethodforMeasuringHeatTransferRateUsing
a Thin-Skin Calorimeter
1.1 This test method describes the measurement of heat
E511 Test Method for Measuring Heat Flux Using a
transfer rate using a thermal capacitance-type calorimeter
Copper-Constantan Circular Foil, Heat-Flux Gage
which assumes one-dimensional heat conduction into a cylin-
drical piece of material (slug) with known physical properties.
3. Summary of Test Method
1.2 This standard does not purport to address all of the
3.1 The measurement of heat transfer rate to a slug or
safety concerns, if any, associated with its use. It is the
thermal capacitance type calorimeter may be determined from
responsibility of the user of this standard to establish appro-
the following data:
priate safety and health practices and determine the applica-
3.1.1 Density and specific heat of the slug material,
bility of regulatory limitations prior to use.
3.1.2 Length or axial distance from the front face of the
1.3 The values stated in SI units are to be regarded as the
cylindrical slug to the back-face thermocouple,
standard.
3.1.3 Slope of the temperature—time curve generated by
NOTE 1—For information see Test Methods E285, E422, E458,
the back-face thermocouple, and
E459, and E511.
3.1.4 Calorimeter temperature history.
3.2 The heat transfer rate is thus determined numerically by
2. Referenced Documents
multiplying the density, specific heat, and length of the slug by
2.1 ASTM Standards:
the slope of the temperature–time curve obtained by the data
E285 Test Method for Oxyacetylene Ablation Testing of
acquisition system (see Eq 1).
Thermal Insulation Materials
3.3 The technique for measuring heat transfer rate by the
E422 Test Method for Measuring Heat Flux Using a
thermal capacitance method is illustrated schematically in Fig.
Water-Cooled Calorimeter
1.Theapparatusshownisatypicalslugcalorimeterwhich,for
E458 Test Method for Heat of Ablation
example, can be used to determine both stagnation region heat
transfer rate and side-wall or afterbody heat transfer rate
values.Theannularinsulatorservesthepurposeofminimizing
heat transfer to or from the body of the calorimeter, thus
This test method is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of SpaceTechnology and is the direct responsibility of
approximating one-dimensional heat flow. The body of the
Subcommittee E21.08 on Thermal Protection.
calorimeter is configured to establish flow and should have the
Current edition approved May 10, 2002. Published December 1996. Originally
same size and shape as that used for ablation models or test
published as E457–72. Last previous edition E457–72(1990)e .
Annual Book of ASTM Standards, Vol 15.03. specimens.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E457–96 (2002)
FIG. 1 Schematic of a Thermal Capacitance (Slug) Calorimeter
3.3.1 For the control volume specified in this test method, a 3.3.2 In order to calculate the initial response time for a
thermal energy balance during the period of initial linear given slug, Eq 2 may be used.
temperature response can be stated as follows:
l rC 2
p
t 5 ln (2)
R 2
EnergyReceivedbytheCalorimeter ~frontface! (1)
qindicated
kp
S D
1 2
qinput
5EnergyConductedAxiallyIntotheSlug
q 5rC l ~DT/Dt! 5 ~MC /A! ~DT/Dt!
c p p
where:
k = thermal conductivity of slug material, W/m·K
where:
2 3.3.3 For maximum linear test time (temperature–time
q˙ = calorimeter heat transfer rate, W/m ,
c
3 curve)withinanallowedsurfacetemperaturelimit,therelation
r = density of slug material, kg/m ,
shownasEq3maybeusedforacalorimeterwhichisinsulated
C = average specific heat of slug material during the
p
by a gap at the back face.
temperature rise (DT), J/kg·K,
l = length or axial distance from front face of slug to
t 50.48 rlC ~DT /q˙! (3)
max,opt. p frontface
the thermocouple location (back-face), m,
where:
DT =(T − T)=calorimeter slug temperature rise dur-
f i
DT = thecalorimeterfinalfrontfacetempera-
front face
ingexposuretoheatsource(linearpartofcurve),
ture minus the initial front face (ambi-
K,
ent) temperature, T .
Dt =(t − t)=time period corresponding to DT tem- o
f i
3.3.4 Eq3isbasedontheoptimumlengthoftheslugwhich
perature rise, s,
can be obtained by applying Eq 4 as follows:
M = mass of the cylindrical slug, kg,
A = cross-sectional area of slug, m .
l 53 k DT /5q˙ (4)
opt. frontface c
In order to determine the steady-state heat transfer rate with
3.4 Tominimizesideheatingorsideheatlosses,thebodyis
athermalcapacitance-typecalorimeter,Eq1mustbesolvedby
separated physically from the calorimeter slug by means of an
using the known properties of the slug material (for example,
insulating gap or a low thermal diffusivity material, or both.
densityandspecificheat)—thelengthoftheslug,andtheslope
The insulating gap that is employed should be small, and
(linear portion) of the temperature–time curve obtained during
recommendedtobenomorethan0.05mmontheradius.Thus,
the exposure to a heat source.The initial and final temperature
transient effects must be eliminated by using the initial linear
portion of the curve (see Fig. 2).
Ledford, R. L., Smotherman,W. E., and Kidd, C.T., “Recent Developments in
Heat-Transfer Rate, Pressure, and Force Measurements for Hotshot Tunnels,”
AEDC-TR-66-228 (AD645764), January 1967.
3 5
“Thermophysical Properties of High Temperature Solid Materials,” TPRC, Kirchhoff, R. H., “Calorimetric Heating-Rate Probe for Maximum-Response-
Purdue University, or “Handbook of Thermophysical Properties,” Tolukian and TimeInterval,” American Institute of Aeronautics and Astronautics Journal,AIAJA,
Goldsmith, MacMillan Press, 1961. Vol 2, No. 5, May 1964, pp. 966–67.
E457–96 (2002)
FIG. 2 Typical Temperature—Time Curve for Slug Calorimeter
if severe pressure variations exist across the face of the transfer rate to the calorimeter can be related to that experi-
calorimeter, side heating caused by flow into or out of the enced by the test specimen.
insulation gap would be minimized. Depending on the size of
4.2 The slug calorimeter is one of many calorimeter con-
the calorimeter surface, variations in heat transfer rate may
cepts used to measure heat transfer rate. This type of calorim-
existacrossthefaceofthecalorimeter;therefore,themeasured
eter is simple to fabricate, inexpensive, and readily installed
heat transfer rate represents an average heat transfer rate over
since it is not water-cooled. The primary disadvantages are its
the surface of the slug.
short lifetime and relatively long cool-down time after expo-
3.5 Since interpretation of the data obtained by this test
suretothethermalenvironment.Inmeasuringtheheattransfer
method is not within the scope of this discussion, such effects
ratetothecalorimeter,accuratemeasurementoftherateofrise
as surface recombination and thermo-chemical boundary layer
in back-face temperature is imperative.
reactions are not considered in this test method.
4.3 In the evaluation of high-temperature materials, slug
3.6 If the thermal capacitance calorimeter is used to mea-
calorimeters are used to measure the heat transfer rate on
sure only radiative heat transfer rate or combined convective/
various parts of the instrumented models, since heat transfer
radiativeheattransferratevalues,thesurfacereflectivityofthe
rate is one of the important parameters in evaluating the
calorimeter should be measured over the wavelength region of
performance of ablative materials.
interest (depending on the source of radiant energy).
4.4 Regardless of the source of thermal energy to the
calorimeter (radiative, convecti
...
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