ASTM E598-08(2020)
(Test Method)Standard Test Method for Measuring Extreme Heat-Transfer Rates from High-Energy Environments Using a Transient, Null-Point Calorimeter
Standard Test Method for Measuring Extreme Heat-Transfer Rates from High-Energy Environments Using a Transient, Null-Point Calorimeter
SIGNIFICANCE AND USE
5.1 The purpose of this test method is to measure extremely high heat-transfer rates to a body immersed in either a static environment or in a high velocity fluid stream. This is usually accomplished while preserving the structural integrity of the measurement device for multiple exposures during the measurement period. Heat-transfer rates ranging up to 2.84 × 102 MW/m2 (2.5 × 104 Btu/ft2-sec) (7) have been measured using null-point calorimeters. Use of copper null-point calorimeters provides a measuring system with good response time and maximum run time to sensor burnout (or ablation). Null-point calorimeters are normally made with sensor body diameters of 2.36 mm (0.093 in.) press-fitted into the nose of an axisymmetric model.
5.2 Sources of error involving the null-point calorimeter in high heat-flux measurement applications are extensively discussed in Refs (3-7). In particular, it has been shown both analytically and experimentally that the thickness of the copper above the null-point cavity is critical. If the thickness is too great, the time response of the instrument will not be fast enough to pick up important flow characteristics. On the other hand, if the thickness is too small, the null-point calorimeter will indicate significantly larger (and time dependent) values than the input or incident heat flux. Therefore, all null-point calorimeters should be experimentally checked for proper time response and calibration before they are used. Although a calibration apparatus is not very difficult or expensive to fabricate, there is only one known system presently in existence (6 and 7). The design of null-point calorimeters can be accomplished from the data in this documentation. However, fabrication of these sensors is a difficult task. Since there is not presently a significant market for null-point calorimeters, commercial sources of these sensors are few. Fabrication details are generally regarded as proprietary information. Some users have developed me...
SCOPE
1.1 This test method covers the measurement of the heat-transfer rate or the heat flux to the surface of a solid body (test sample) using the measured transient temperature rise of a thermocouple located at the null point of a calorimeter that is installed in the body and is configured to simulate a semi-infinite solid. By definition the null point is a unique position on the axial centerline of a disturbed body which experiences the same transient temperature history as that on the surface of a solid body in the absence of the physical disturbance (hole) for the same heat-flux input.
1.2 Null-point calorimeters have been used to measure high convective or radiant heat-transfer rates to bodies immersed in both flowing and static environments of air, nitrogen, carbon dioxide, helium, hydrogen, and mixtures of these and other gases. Flow velocities have ranged from zero (static) through subsonic to hypersonic, total flow enthalpies from 1.16 to greater than 4.65 × 101 MJ/kg (5 × 10 2 to greater than 2 × 104 Btu/lb.), and body pressures from 105 to greater than 1.5 × 107 Pa (atmospheric to greater than 1.5 × 102 atm). Measured heat-transfer rates have ranged from 5.68 to 2.84 × 102 MW/m2 (5 × 102 to 2.5 × 104 Btu/ft2-sec).
1.3 The most common use of null-point calorimeters is to measure heat-transfer rates at the stagnation point of a solid body that is immersed in a high pressure, high enthalpy flowing gas stream, with the body axis usually oriented parallel to the flow axis (zero angle-of-attack). Use of null-point calorimeters at off-stagnation point locations and for angle-of-attack testing may pose special problems of calorimeter design and data interpretation.
1.4 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 appli...
General Information
Relations
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: E598 −08 (Reapproved 2020)
Standard Test Method for
Measuring Extreme Heat-Transfer Rates from High-Energy
Environments Using a Transient, Null-Point Calorimeter
This standard is issued under the fixed designation E598; 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 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This test method covers the measurement of the heat-
ization established in the Decision on Principles for the
transfer rate or the heat flux to the surface of a solid body (test
Development of International Standards, Guides and Recom-
sample) using the measured transient temperature rise of a
mendations issued by the World Trade Organization Technical
thermocouple located at the null point of a calorimeter that is
Barriers to Trade (TBT) Committee.
installed in the body and is configured to simulate a semi-
infinite solid. By definition the null point is a unique position
2. Referenced Documents
on the axial centerline of a disturbed body which experiences
2.1 ASTM Standards:
the same transient temperature history as that on the surface of
E422Test Method for Measuring Heat Flux Using a Water-
a solid body in the absence of the physical disturbance (hole)
Cooled Calorimeter
for the same heat-flux input.
E511TestMethodforMeasuringHeatFluxUsingaCopper-
1.2 Null-point calorimeters have been used to measure high
Constantan Circular Foil, Heat-Flux Transducer
convective or radiant heat-transfer rates to bodies immersed in
both flowing and static environments of air, nitrogen, carbon 3. Terminology
dioxide, helium, hydrogen, and mixtures of these and other
3.1 Symbols:
gases. Flow velocities have ranged from zero (static) through
subsonic to hypersonic, total flow enthalpies from 1.16 to a = Radius of null-point cavity, m (in.)
1 2 4
greater than 4.65×10 MJ/kg (5×10 to greater than 2×10 b = Distancefromfrontsurfaceofnull-pointcalorimeterto
5 7
the null-point cavity, m (in.)
Btu/lb.), and body pressures from 10 to greater than 1.5×10
C = Specific heat capacity, J/kg–K (Btu/lb-°F)
Pa (atmospheric to greater than 1.5×10 atm). Measured
p
d = Diameter of null-point cavity, m (in.)
heat-transfer rates have ranged from 5.68 to 2.84×10 MW/
2 2 4 2
k = Thermal conductivity, W/m–K (Btu/in.-sec-°F)
m (5×10 to 2.5×10 Btu/ft -sec).
L = Length of null-point calorimeter, m (in.)
1.3 The most common use of null-point calorimeters is to
q = Calculated or measured heat flux or heat-transfer-rate,
2 2
measure heat-transfer rates at the stagnation point of a solid
W/m (Btu/ft -sec)
2 2
bodythatisimmersedinahighpressure,highenthalpyflowing
q = Constantheatfluxorheat-transfer-rate,W/m (Btu/ft -
gas stream, with the body axis usually oriented parallel to the
sec)
flow axis (zero angle-of-attack). Use of null-point calorimeters
R = RadialdistancefromaxialcenterlineofTRAXanalyti-
at off-stagnation point locations and for angle-of-attack testing
cal model, m (in.)
may pose special problems of calorimeter design and data
r = Radial distance from axial centerline of null-point
interpretation.
cavity, m (in.)
T = Temperature, K (°F)
1.4 This standard does not purport to address all of the
T = Temperature on axial centerline of null point, K (°F)
b
safety concerns, if any, associated with its use. It is the
T = Temperature on surface of null-point calorimeter, K
s
responsibility of the user of this standard to establish appro-
(°F)
priate safety, health, and environmental practices and deter-
t = Time, sec
mine the applicability of regulatory limitations prior to use.
Z = Distance in axial direction of TRAX analytical model,
m (in.)
This test method is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of SpaceTechnology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2020. Published December 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approvedin1977.Lastpreviouseditionapprovedin2015asE598–08(2015).DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E0598-08R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E598 − 08 (2020)
2 2
However,theidentificationanddocumentationofthemeasure-
α = Thermal diffusivity, m /sec (in. /sec)
3 3
ment concept was a major step in leading others to adapt this
ρ = Density, kg/m (lb⁄in. )
concept to the transient measurement of high heat fluxes in
4. History of Test Method
ground test facilities.
4.1 FromliteraturereviewsitappearsthatMastersandStein
4.2 Beck and Hurwicz (2) expanded the analysis of Masters
(1) werethefirsttodocumenttheresultsofananalyticalstudy
and Stein to include steady-state solutions and were the first to
of the temperature effects of axial cavities drilled from the
label the method of measurement “the null-point concept.”
backsideofawallwhichisheatedonthefrontsurface(seeFig.
They effectively used a digital computer to generate relatively
1). These investigators were primarily concerned with the
large quantities of analytical data from numerical methods.
deviation of the temperature measured in the bottom of the
Beck and Hurwicz computed errors due to relatively large
cavity from the undisturbed temperature on the heated surface.
thermocouplewiresintheaxialcavityandwereabletosuggest
Since they were not in possession of either the computing
that the optimum placement of the thermocouple in the cavity
powerorthenumericalheatconductioncodesnowavailableto
occurred when the ratio a/b was equal to 1.1. However, their
the analyst, Masters and Stein performed a rigorous math-
analysislikethatofMastersandSteinwasonlyconcernedwith
ematical treatment of the deviation of the transient
the deviation of the temperature in the axial cavity and did not
temperature, T , on the bottom centerline of the cavity of
b
address the error in measured heat flux.
radius, a, and thickness, b, from the surface temperature T .
s
The results of Masters and Stein indicated that the error in 4.3 Howey and DiCristina (3) were the first to perform an
temperature measurement on the bottom centerline of the
actual thermal analysis of this measurement concept.Although
cavity would decrease with increasing values of a/b and also
the explanation of modeling techniques is somewhat ambigu-
decrease with increasing values of the dimensionless time,
ous in their paper, it is obvious that they used a finite element,
αt/b , where αis the thermal diffusity of the wall material.
two dimensional axisymmetric model to produce temperature
Theyalsoconcludedthatthemostimportantfactorintheerror
profiles in a geometry simulating the null-point calorimeter.
intemperaturemeasurementwastheratio a/bandtheerrorwas
Temperature histories at time intervals down to 0.010 sec were
independent of the level of heat flux. The conclusions of
obtained for a high heat-flux level on the surface of the
Masters and Stein may appear to be somewhat elementary
analytical model. Although the analytical results are not
compared with our knowledge of the null-point concept today.
presented in a format which would help the user/designer
optimize the sensor design, the authors did make significant
general conclusions about null point calorimeters. These in-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
clude: (1) “., thermocouple outputs can yield deceivingly fast
this test method.
NOTE 1—1-T (0,t)=Surface temperature (x=0) of a solid, semi-infinite slab at some time, t.
s
NOTE 2—2-T (0,b,t)=Temperature at r=0, x=b of a slab with a cylindrical cavity at some time, t, heat flux, q, the same in both cases.
b
FIG. 1 Semi-infinite Slab with Cylindrical Cavity
E598 − 08 (2020)
response rates and erroneously high heating rates (+18%) graphically illustrated on Figs. 3 and 4. The optimum value of
when misused in inverse one-dimensional conduction solu- the ratio a/b is defined to be that number which yields the
fastest time response to a step heat-flux input and maintains a
tions.” (2) “The prime reason for holding the thermocouple
depth at R/E =1.1 is to maximize thermocouple response at constant value of indicated q˙/input q˙ after the initial time
response period. From Figs. 3 and 4, it can be seen that this
high heating rates for the minimum cavity depth.” (Note:
optimum value is about 1.4 for two families of curves for
Rand Eas used by Howey and DeChristina are the same terms
which the cavity radius, a, is held constant while the cavity
as aand bwhicharedefinedin4.1andareusedthroughoutthis
thickness, b,isvariedtospanawiderangeoftheratio a/b.This
document.) (3)Afinite length null-point calorimeter body may
is a slightly higher value than reported by earlier analysts. It is
be considered semi-infinite for:
important to note that the analytical results do not necessarily
~αt!
#0.3 have to give a value of indicated q˙/input q˙ =1.0 since this
L
difference can be calibrated in the laboratory. The data graphi-
4.4 Powars, Kennedy, and Rindal (4 and 5) were the first to
cally illustrated on Figs. 3 and 4 and substantiate conclusions
document using null point calorimeters in the swept mode.
drawn by the authors of Refs (3 and 4) that the calculated heat
This method which is now used in almost all arc facilities has
flux can be considerably higher than the actual input heat
the advantages of (1) measuring the radial distributions across
flux—especially as the ratio of a/b is raised consistently above
the arc jet, and (2) preserving the probe/sensor structural
1.5.All of the users of null-point calorimeters assume that the
integrity for repeated measurements. This technique involves
device simulates a semi-infinite body in the time period of
sweeping the probe/sensor through the arc-heated flow field at
interest. Therefore, the sensor is subject to the finite body
1/2
a rate slow enough to allow the sensor to make accurate
length, L, defined by L/(αt) ≤ 1.8 in order that the error in
measurements, yet fast enough to prevent model ablation.
indicated heat flux does not exceed one percent (6 and 7).This
4.4.1 Following the pattern of Howey and DiCristina, Pow- restriction agrees well with the earlier work of Howey and
ars et. al. stressed the importance of performing thermal DiCristina (3).
analyses to “characterize the response of a typical real null
4.6 Asectionviewsketchofatypicalnull-pointcalorimeter
point calorimeter to individually assess a variety of potential
showing all important components and the physical configu-
errors,.”. Powars et. al. complain that Howey & DiCristina
ration of the sensor is shown in Fig. 5.The outside diameter is
“. report substantial errors in some cases, but present no
2.36 mm (0.093 in.), the length is 10.2 mm (0.40 in.), and the
generalized results or design guide lines.” They state concern-
body material is oxygen-free high conductivity (OFHC) cop-
ing the analyses performed to support their own
per. Temperature at the null point is measured by a 0.508 mm
documentation, “In order to establish guidelines for null point
(0.020 in.) diam American National Standards Association
calorimeter design and data reduction, analyses were per-
(ANSI) type K stainless steel-sheathed thermocouple with
formed to individually assess the measurement errors associ-
0.102 mm (0.004 in.) diam thermoelements. Although no
atedwithavarietyofnon-idealaspectsofactualcalorimeters.”
thermocouple attachment is shown, it is assumed that the
The conclusions reached from the results of the thermal
individual thermocouple wires are in perfect contact with the
analyses were broken down into eight sub headings and were
backsideofthecavityandpresentnoaddedthermalmasstothe
discussed individually. Some of the conclusions reached were
system. Details of installing thermocouples in the null point
rather elementary and were previously reported in Refs (1-3).
cavity and making a proper attachment of the thermocouple
Others were somewhat arbitrary and were stated without
with the copper slug are generally considered to be proprietary
substantiating data. One specific conclusion concerns the ratio
by the sensor manufacturers. Kidd in Ref (7) states that the
of the null-point cavity radius, a, to the cavity thickness, b.
attachment is made by thermal fusion without the addition of
Whilestatingthattheoptimumconditionoccurredwhen a= b,
foreign materials. Note that the null-point body has a small
the authors of Ref (4)further state that when a=0.305 mm
flange at the front and back which creates an effective dead air
(0.012 in.) and b=0.127 mm (0.005 in.); a/b=2.4, the
space along the length of the cylinder to enhance one-
calculated heat flux will be 20% higher than the actual heat
dimensional heat conduction and prevent radial conduction.
flux. In more recent documentation using more accurate and
For aerodynamic heat-transfer measurements, the null-point
sophisticated heat conduction computer codes as well as an
sensors are generally pressed into the stagnation position of a
establishednumericalinverseheatconductionequation (6),the sphere cone model of the same material (OFHC copper).
error in indicated heat flux is shown to be considerably higher
4.7 The value of the lumped thermal parameter of copper is
than 20% and is highly time dependent.
not a strong function of temperature. In fact, the value of
1/2
(ρC k) for OFHC copper varies less than three percent from
p
4.5 The latest and most comprehensive thermal analysis of
room temperature to the melting point, 1356 K (1981°F); (see
the null-point calorimeter concept was performed by Kidd and
Fig. 6). Thermal properties of OFHC copper are well docu-
documented in Refs (6 and 7). This analytical work was
mented and data from different sources are in good agreement
accomplished by using a finite element axisymmetric heat
(8). Most experimenters use the room temperature value of the
conduction code (7). The finite element model simulating the
parameter in processing data from null-point calorimeters.
null-point calorimeter system is comprised of 793 finite ele-
ments and 879 nodal points and is shown in block diagram 4.8 The determi
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.