ASTM E434-10

Standard Test Method for Calorimetric Determination of Hemispherical Emittance and the Ratio of Solar Absorptance to Hemispherical Emittance Using Solar Simulation

ABSTRACT
This test method covers measurement techniques for calorimetrically determining the ratio of solar absorptance to hemispherical emittance using a steady-state method, and for calorimetrically determining the total hemispherical emittance using a transient technique. The main elements of the apparatus include a vacuum system, a cold shroud within the vacuum chamber, instrumentation for temperature measurement, and a solar simulator. Any type of coating may be tested by this test method provided its structure remains stable in vacuum over the temperature range of interest. The substrate shall be machined from flat stock and to a size proportioned to the working area of the chamber.
SCOPE
1.1 This test method covers measurement techniques for calorimetrically determining the ratio of solar absorptance to hemispherical emittance using a steady-state method, and for calorimetrically determining the total hemispherical emittance using a transient technique.
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.

General Information

• Status: Historical
• Publication Date: 31-Oct-2010
• Technical Committee: E21 - Space Simulation and Applications of Space Technology
• Drafting Committee: E21.04 - Space Simulation Test Methods

Relations

• Replaces: ASTM E434-71(2002) - Standard Test Method for Calorimetric Determination of Hemispherical Emittance and the Ratio of Solar Absorptance to Hemispherical Emittance Using Solar Simulation
• Effective Date: 01-Nov-2010
• Referred By: ASTM E781-86(2023) - Standard Practice for Evaluating Absorptive Solar Receiver Materials When Exposed to Conditions Simulating Stagnation in Solar Collectors with Cover Plates
• Effective Date: 01-Nov-2010
• Referred By: ASTM E512-94(2020) - Standard Practice for Combined, Simulated Space Environment Testing of Thermal Control Materials with Electromagnetic and Particulate Radiation
• Effective Date: 01-Nov-2010
• Referred By: ASTM E744-07(2022) - Standard Practice for Evaluating Solar Absorptive Materials for Thermal Applications
• Effective Date: 01-Nov-2010

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E434 − 10
StandardTest Method for
Calorimetric Determination of Hemispherical Emittance and
the Ratio of Solar Absorptance to Hemispherical Emittance
1
Using Solar Simulation
This standard is issued under the fixed designation E434; 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 the specimen to the surroundings cause the specimen to reach
anequilibriumtemperaturethatisdependentupontheα/εratio
1.1 This test method covers measurement techniques for
of its surface.
calorimetrically determining the ratio of solar absorptance to
hemispherical emittance using a steady-state method, and for 3.3 In the dynamic radiative method of measuring total
calorimetrically determining the total hemispherical emittance hemispherical emittance, the specimen is heated with a solar
using a transient technique. simulation source and then allowed to cool by radiation to an
evacuated space chamber with an inside effective emittance of
1.2 This standard does not purport to address all of the
unity.Fromaknowledgeofthespecificheatofthespecimenas
safety concerns, if any, associated with its use. It is the
a function of temperature, the area of the test specimen, its
responsibility of the user of this standard to establish appro-
mass,itscoolingrate,andthetemperatureofthewalls,itstotal
priate safety and health practices and determine the applica-
hemispherical emittance may be calculated as a function of
bility of regulatory limitations prior to use.
temperature.
2. Referenced Documents
4. Apparatus
2
2.1 ASTM Standards:
4.1 The main elements of the apparatus include a vacuum
E349Terminology Relating to Space Simulation
system, a cold shroud within the vacuum chamber, instrumen-
3. Summary of Test Method tation for temperature measurement, and a solar simulator.
3.1 In calorimetric measurements of the radiative properties 4.2 Theareaofthethermalshroudshallnotbelessthan100
of materials, the specimen under evaluation is placed in a
timesthespecimenarea(controlledbythespecimensize).The
vacuum environment under simulated solar radiation with cold inner surfaces of the chamber shall have a high solar absorp-
surroundings. By observation of the thermal behavior of the
tance (not less than 0.96) and a total hemispherical emittance
3
specimen the thermophysical properties may be determined by of at least 0.88 (painted with a suitable black paint), and shall
an equation that relates heat balance considerations to measur-
be diffuse. Suitable insulated standoffs shall be provided for
able test parameters. suspending the specimen. Thermocouple wires shall be con-
nected to a vacuumtight fitting where the temperature of
3.2 In a typical measurement, to determine α/ε as defined in
feedthrough is uniform. Outside of the chamber, all thermo-
Definitions E349, the side of the specimen in question is
couples shall connect with a fixed cold junction.
exposed to a simulated solar source, through a port having
suitable transmittance over the solar spectrum. This port, or 4.3 The chamber shall be evacuated to a pressure of
−6
window, must be of sufficient diameter that the specimen and
1×10 torr (0.1 mPa) or less at all times.
radiation monitor will be fully irradiated and must be of
4.4 The walls of the inner shroud shall be in contact with
sufficient thickness that it will maintain its strength without
coolant so that their temperature can be maintained uniform at
deformation under vacuum conditions. The radiant energy
all times.
absorbedbythespecimenfromthesolarsourceandemittedby
4.5 A shutter shall be provided in one end of the chamber
which can be opened to admit a beam of radiant energy from
1
This test method is under the jurisdiction of ASTM Committee E21 on Space
a solar simulator. When open, this shutter shall provide an
Simulation andApplications of SpaceTechnology and is the direct responsibility of
apertureadmittingthefullsimulatorbeam.Whentheshutteris
Subcommittee E21.04 on Space Simulation Test Methods.
Current edition approved Nov. 1, 2010. Published December 2010. Originally
approved in 1971. Last previous edition approved in 2002 as E434–71 (2002).
3
DOI: 10.1520/E0434-10. Nextel Brand Velvet Coating 401-C10 Black, available from Reflective
2
Annual Book of ASTM Standards, Vol 15.03. Products Div., 3M Co., has been found to be satisfactory.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E434 − 10
closed,allraysemittedbythespecimenshallbeinterceptedby in the back of the specimen (one wire in
...

This document is not anASTM standard and is intended only to provide the user of anASTM 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:E434–71 (Reapproved 2002) Designation:E434–10
Standard Test Method for
Calorimetric Determination of Hemispherical Emittance and
the Ratio of Solar Absorptance to Hemispherical Emittance
1
Using Solar Simulation
This standard is issued under the fixed designation E434; 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
1.1 This test method covers measurement techniques for calorimetrically determining the ratio of solar absorptance to
hemispherical emittance using a steady-state method, and for calorimetrically determining the total hemispherical emittance using
a transient technique.
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.
2. Referenced Documents
2
2.1 ASTM Standards:
E349 Terminology Relating to Space Simulation
3. Summary of Test Method
3.1 In calorimetric measurements of the radiative properties of materials, the specimen under evaluation is placed in a vacuum
environment under simulated solar radiation with cold surroundings. By observation of the thermal behavior of the specimen the
thermophysicalpropertiesmaybedeterminedbyanequationthatrelatesheatbalanceconsiderationstomeasurabletestparameters.
3.2 In a typical measurement, to determine a/´ as defined in Definitions E349, the side of the specimen in question is exposed
to a simulated solar source, through a port having suitable transmittance over the solar spectrum. This port, or window, must be
ofsufficientdiameterthatthespecimenandradiationmonitorwillbefullyirradiatedandmustbeofsufficientthicknessthatitwill
maintain its strength without deformation under vacuum conditions. The radiant energy absorbed by the specimen from the solar
source and emitted by the specimen to the surroundings cause the specimen to reach an equilibrium temperature that is dependent
upon the a/´ ratio of its surface.
3.3 Inthedynamicradiativemethodofmeasuringtotalhemisphericalemittance,thespecimenisheatedwithasolarsimulation
source and then allowed to cool by radiation to an evacuated space chamber with an inside effective emittance of unity. From a
knowledge of the specific heat of the specimen as a function of temperature, the area of the test specimen, its mass, its cooling
rate, and the temperature of the walls, its total hemispherical emittance may be calculated as a function of temperature.
4. Apparatus
4.1 The main elements of the apparatus include a vacuum system, a cold shroud within the vacuum chamber, instrumentation
for temperature measurement, and a solar simulator.
4.2 The area of the thermal shroud shall not be less than 100 times the specimen area (controlled by the specimen size). The
innersurfacesofthechambershallhaveahighsolarabsorptance(notlessthan0.96)andatotalhemisphericalemittanceofatleast
3
0.88 (painted with a suitable black paint), and shall be diffuse. Suitable insulated standoffs shall be provided for suspending the
specimen. Thermocouple wires shall be connected to a vacuumtight fitting where the temperature of feedthrough is uniform.
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 E21.04 on Space Simulation Test Methods.
Current edition approved April 10, 2002. Published April 2002. Originally approved in 1971. Last previous edition approved in 1996 as E434–71 (1996). DOI:
10.1520/E0434-71R02.
Current edition approved Nov. 1, 2010. Published December 2010. Originally approved in 1971. Last previous edition approved in 2002 as E434–71 (2002). DOI:
10.1520/E0434-10.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,[e-mail] Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
2
Annual Book of ASTM Standards, Vol 15.03.
3
Nextel Brand Velvet Coating 401-C10 Black, available from Reflective Products Div., 3M Co., has been found to be satisfactory.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

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