ASTM E457-08(2020)
(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
4.1 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.
4.2 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.
4.3 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.
4.4 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...
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
Note 1: For information see Test Methods E285, E422, E458, E459, and E511.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E457 − 08 (Reapproved 2020)
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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope E458Test Method for Heat of Ablation
E459Test Method for Measuring Heat Transfer Rate Using
1.1 This test method describes the measurement of heat
a Thin-Skin Calorimeter
transfer rate using a thermal capacitance-type calorimeter
E511TestMethodforMeasuringHeatFluxUsingaCopper-
which assumes one-dimensional heat conduction into a cylin-
Constantan Circular Foil, Heat-Flux Transducer
drical piece of material (slug) with known physical properties.
1.2 The values stated in SI units are to be regarded as
3. Summary of Test Method
standard. No other units of measurement are included in this
3.1 The measurement of heat transfer rate to a slug or
standard.
thermal capacitance type calorimeter may be determined from
NOTE 1—For information see Test Methods E285, E422, E458, E459,
the following data:
and E511.
3.1.1 Density and specific heat of the slug material,
1.3 This standard does not purport to address all of the
3.1.2 Length or axial distance from the front face of the
safety concerns, if any, associated with its use. It is the
cylindrical slug to the back-face thermocouple,
responsibility of the user of this standard to establish appro-
3.1.3 Slope of the temperature—time curve generated by
priate safety, health, and environmental practices and deter-
the back-face thermocouple, and
mine the applicability of regulatory limitations prior to use.
3.1.4 Calorimeter temperature history.
1.4 This international standard was developed in accor-
3.2 The heat transfer rate is thus determined numerically by
dance with internationally recognized principles on standard-
multiplyingthedensity,specificheat,andlengthoftheslugby
ization established in the Decision on Principles for the
the slope of the temperature–time curve obtained by the data
Development of International Standards, Guides and Recom-
acquisition system (see Eq 1).
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3.3 The technique for measuring heat transfer rate by the
thermal capacitance method is illustrated schematically in Fig.
2. Referenced Documents
1.Theapparatusshownisatypicalslugcalorimeterwhich,for
2.1 ASTM Standards:
example, can be used to determine both stagnation region heat
E285Test Method for Oxyacetylene Ablation Testing of
transfer rate and side-wall or afterbody heat transfer rate
Thermal Insulation Materials
values.Theannularinsulatorservesthepurposeofminimizing
E422Test Method for Measuring Heat Flux Using a Water-
heat transfer to or from the body of the calorimeter, thus
Cooled Calorimeter
approximating one-dimensional heat flow. The body of the
calorimeter is configured to establish flow and should have the
same size and shape as that used for ablation models or test
This test method is under the jurisdiction of ASTM Committee E21 on Space
specimens.
Simulation andApplications of SpaceTechnology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection. 3.3.1 For the control volume specified in this test method, a
Current edition approved Nov. 1, 2020. Published December 2020. Originally
thermal energy balance during the period of initial linear
approvedin1972.Lastpreviouseditionapprovedin2015asE457–08(2015).DOI:
temperatureresponsewhereheatlossesareassumednegligible
10.1520/E0457-08R20.
can be stated as follows:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
EnergyReceivedbytheCalorimeter frontface
~ !
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 5EnergyConductedAxiallyIntotheSlug
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E457 − 08 (2020)
FIG. 1 Schematic of a Thermal Capacitance (Slug) Calorimeter
q 5 ρC l ∆T/∆τ 5 MC /A ∆T/∆τ (1) where:
~ ! ~ !~ !
c p p
k = thermal conductivity of slug material, W/m·K
where:
q = q that would be measured at the back-face of the
indicated
q˙ = calorimeter heat transfer rate, W/m ,
c
slug by Eq 1, W/m
ρ = density of slug material, kg/m ,
q = constant q at the front-face of the slug begin-
input input
C = average specific heat of slug material during the
p 2
ning at τ=0,W/m
temperature rise (∆T), J/kg·K,
l = length or axial distance from front face of slug to the
3.3.3 Although the goal of good slug calorimeter design is
thermocouple location (back-face), m,
to minimize heat losses, there can be heating environments,
∆T =(T − T)=calorimeter slug temperature rise during
f i such as very high heat fluxes, where even a good slug
exposure to heat source (linear part of curve), K,
calorimeter design cannot meet the recommended 5 % maxi-
∆τ =(τ − τ)=timeperiodcorrespondingto∆Ttemperature
f i
mum heat loss criterion of 6.1. Also, this criterion only deals
rise, s,
with heat losses measured during the cooling phase, not losses
M = mass of the cylindrical slug, kg,
duringtheheatingphase,whichcanbegreaterthanthecooling
A = cross-sectional area of slug, m .
losses. Under these circumstances, significant heat losses from
In order to determine the steady-state heat transfer rate with
slug to holder during the heating phase, as well as other
athermalcapacitance-typecalorimeter,Eq1mustbesolvedby
possible decaying processes such as a drop in surface
using the known properties of the slug material (for example,
catalycity, can cause the Temperature-Time slope to decrease
densityandspecificheat)—thelengthoftheslug,andtheslope
significantly more than can be accounted for by the increasing
(linear portion) of the temperature–time curve obtained during
heat capacity with temperature of the Copper slug alone,
the exposure to a heat source.The initial and final temperature
makingitimportantthattheslopebetakenearlyintheprocess
transient effects must be eliminated by using the initial linear
before the losses lower the slope too much, introducing more
portion of the curve (see Fig. 2).
error to the downside on the heat flux calculated (see Fig. 3).
3.3.2 In order to calculate the initial response time for a
The degree of losses affect the exact position where the best
given slug, Eq 2 may be used. This equation is based on the
slope begins to occur, but typically it should be expected at
idealization of zero heat losses from slug to its holder.
about time τ = τ calculated by Eq 2 for q /q = 0.99,
R indicated input
which value of τ is abbreviated as τ . Fig. 2 and Fig. 3
l ρC 2 R R0.99
p
τ 5 ln (2)
R 2 assume that “heat source on” is a step function. This is an
kπ q indicated
S D
1 2
idealization, but the reality can be significantly different. For
q input
example, in some cases a calorimeter may experience a higher
heat flux prior to reaching its final position in the heat source,
which can cause the initial maximum slope to be higher than
“Thermophysical Properties of High Temperature Solid Materials,” TPRC,
Purdue University, or “Handbook of Thermophysical Properties,” Tolukian and
what is wanted for the calculation of the heat flux at the final
Goldsmith, MacMillan Press, 1961.
position. Therefore, it is important to note that “zero” time, to
Ledford, R. L., Smotherman,W. E., and Kidd, C.T., “Recent Developments in
which τ is added to determine where to start looking for
Heat-Transfer Rate, Pressure, and Force Measurements for Hotshot Tunnels,” R0.99
AEDC-TR-66-228 (AD645764), January 1967. the desired slope, is when the calorimeter has reached its final
E457 − 08 (2020)
FIG. 2 Typical Temperature–Time Curve for Slug Calorimeter
FIG. 3 Temperature–Time Curve when Heat and Other Items are Significant During Heating Phase
positionwhereitisdesiredtomeasuretheheatflux.Therefore, Should more accurate results be required, the losses form the
choosingthebestplacetotaketheslopecanbeveryimportant.
E457 − 08 (2020)
slugshouldbemodeledandaccountedforbyacorrectionterm short lifetime and relatively long cool-down time after expo-
in the energy balance equation. suretothethermalenvironment.Inmeasuringtheheattransfer
3.3.4 For maximum linear test time (temperature–time ratetothecalorimeter,accuratemeasurementoftherateofrise
curve)withinanallowedsurfacetemperaturelimit,therelation in back-face temperature is imperative.
shownasEq3maybeusedforacalorimeterwhichisinsulated
4.3 In the evaluation of high-temperature materials, slug
by a gap at the back face.
calorimeters are used to measure the heat transfer rate on
τ 50.48ρlC ~∆T /q˙ ! (3) various parts of the instrumented models, since heat transfer
max,opt. p frontface
rate is one of the important parameters in evaluating the
where:
performance of ablative materials.
∆T = the calorimeter final front face temperature
front face
4.4 Regardless of the source of thermal energy to the
minus the initial front face (ambient)
calorimeter (radiative, convective, or a combination thereof)
temperature, T .
o
the measurement is averaged over the calorimeter surface. If a
3.3.5 Eq3isbasedontheoptimumlengthoftheslugwhich
significant percentage of the total thermal energy is radiative,
can be obtained by applying Eq 4 as follows:
consideration should be given to the emissivity of the slug
l 53 k ∆T /5q˙ (4) surface. If non-uniformities exist in the input energy, the heat
opt. frontface c
transfer rate calorimeter would tend to average these varia-
3.4 Tominimizesideheatingorsideheatlosses,thebodyis
tions; therefore, the size of the sensing element (that is, the
separated physically from the calorimeter slug by means of an
slug) should be limited to small diameters in order to measure
insulating gap or a low thermal diffusivity material, or
...
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