Overview of materials and coatings emission coefficient control methods
The emissivity of a coating and materials determines the intensity of radiation heat exchange on the surface of the object under study. Therefore experimental determination is important to ensure the necessary thermal protection characteristics of structures. The article considers methods of emissiv...
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| Дата: | 2022 |
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General Energy Institute of the National Academy of Sciences of Ukraine
2022
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Репозитарії
System Research in Energy| _version_ | 1871104140590972928 |
|---|---|
| author | Dekusha, Oleg Kovtun , Svitlana Burova , Zinaida |
| author_facet | Dekusha, Oleg Kovtun , Svitlana Burova , Zinaida |
| author_institution_txt_mv | [
{
"author": "Oleg Dekusha",
"institution": null
},
{
"author": "Svitlana Kovtun ",
"institution": null
},
{
"author": "Zinaida Burova ",
"institution": null
}
] |
| author_sort | Dekusha, Oleg |
| baseUrl_str | https://systemre.org/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-18T12:57:43Z |
| description | The emissivity of a coating and materials determines the intensity of radiation heat exchange on the surface of the object under study. Therefore experimental determination is important to ensure the necessary thermal protection characteristics of structures. The article considers methods of emissivity control, which are currently regulated by the main standards ASTM E408-13, ISO 9050:2003, C835-06, C1371-15. The methods of experimental determination of the emissivity can be divided into two large groups: optical and thermal. Spectrometric is the most widespread optical method. The technique of spectrometric research in determining the curve of specular reflection, measured in a wide range of wavelengths at an angle of incidence of the radiation close to normal. Based on the obtained results, the average value of the normal and hemispherical emissivity of the surface is calculated. Among the thermal methods of experimental determination of the emissivity the following have become widespread: radiation, calorimetric, regular mode method, and the method of continuous heating at a constant rate. The stationary systems with a wide range of research temperatures and portable express devices for control at temperatures close to room temperature are used to measure the emissivity. In stationary systems for measuring the emissivity, which apply thermal methods, heat fluxes between the object under investigation and some emitter, as well as the temperature of the structure elements, are usually determined. But these methods cannot be used in the control of products. Therefore, it is promising to develop a method for measuring the emissivity which will non-destructive and in same do not require additional standard samples for comparations. |
| doi_str_mv | 10.15407/srenergy2022.02.053 |
| first_indexed | 2026-03-24T02:02:23Z |
| format | Article |
| fulltext |
53
Overview of materials and coatings emission coefficient control methods
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71)
1. Introduction
The issue of measuring the emissivity is rele-
vant for many spheres of the national economy. It
is known that about 40% of all extracted organic
fuel is spent on heating residential and industrial
buildings [1]. At the same time, more than 60% of
thermal energy losses occur through the enclosing
structures, which are determined by the conditions
of heat exchange with the surrounding environment.
The emissivity of a coating or material largely de-
termines the intensity of radiation heat exchange
on the surface of the object under study, therefore
its experimental determination is important to en-
sure the necessary thermal protection characteris-
tics of structures. The problem of creating advanced
heat-saving technologies and materials with a given
emission coeffi cient and means of measuring this
parameter is relevant all over the world.
When creating modern energy-effi cient windows
and double-glazed windows low-emission glass is
used. Which ensures a decrease in the radiation com-
ponent of heat exchange and accordingly an increase
in heat transfer resistance compared to ordinary trans-
lucent structures. For space vehicles on the contrary
the shell should contribute to the dispersion in space
of the heat released in the on-board equipment, but
have a low coeffi cient of absorption of solar radiation.
When implementing technology for the production of
energy-effi cient glass and shells for space vehicles, as
well as for determining the characteristics of products
surfaces it is relevant to carry out express control of
the emissivity [2–6].
Known modern methods of determining the emis-
sivity use either complex and expensive spectro-
metric equipment, or calorimetric methods which
in order to reduce the convective component of heat
exchange involve vacuuming the chamber with the
samples under study. For the most part devices for ex-
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71): 53–63
https://doi.org/10.15407/srenergy2022.02.053
UDC 536.629.7:536.2:536.6 Oleg Dekusha1*, PhD (Engin.), Senior Researcher, https://orcid.org/0000-0003-3836-0485
Svitlana Kovtun, Dr. Sci. (Engin.), Senior Researcher, https://orcid.org/0000-0002-6596-3460
Zinaida Burova2, PhD (Engin.), Associate Professor, https://orcid.org/0000-0002-4712-6298
1General Energy Institute of NAS of Ukraine, 172, Antonovycha Str., 03150, Kyiv, Ukraine;
e-mail: info@ienergy.kiev.ua
2National University of Life and Environmental Sciences of Ukraine; 15, Heroyiv Oborony Str., 03041, Kyiv, Ukraine
e-mail: rectorat@nubip.edu.ua
* Corresponding author: olds@ukr.net
OVERVIEW OF MATERIALS AND COATINGS EMISSION
COEFFICIENT CONTROL METHODS
Abstract. The emissivity of a coating and materials determines the intensity of radiation heat
exchange on the surface of the object under study. Therefore experimental determination
is important to ensure the necessary thermal protection characteristics of structures. The
article considers methods of emissivity control, which are currently regulated by the main
standards ASTM E408-13, ISO 9050:2003, C835–06, C1371–15. The methods of exper-
imental determination of the emissivity can be divided into two large groups: optical and
thermal. Spectrometric is the most widespread optical method. The technique of spectro-
metric research in determining the curve of specular reflection, measured in a wide range
of wavelengths at an angle of incidence of the radiation close to normal. Based on the ob-
tained results, the average value of the normal and hemispherical emissivity of the surface is
calculated. Among the thermal methods of experimental determination of the emissivity the
following have become widespread: radiation, calorimetric, regular mode method, and the
method of continuous heating at a constant rate. The stationary systems with a wide range
of research temperatures and portable express devices for control at temperatures close to
room temperature are used to measure the emissivity. In stationary systems for measuring
the emissivity, which apply thermal methods, heat fluxes between the object under investi-
gation and some emitter, as well as the temperature of the structure elements, are usually
determined. But these methods cannot be used in the control of products. Therefore, it is
promising to develop a method for measuring the emissivity which will non-destructive and
in same do not require additional standard samples for comparations.
Keywords: express control; emissivity; emissometers; spectrophotometers; reflectometers.
© O. DEKUSHA, S. KOVTUN, Z. BUROVA, 2022
54
O. DEKUSHA, S. KOVTUN, Z. BUROVA
ISSN 2786-7102 (Online). Системні дослідження в енергетиці. 2022. 2(71)
press control have a relatively narrow spectral range
and a limited directional pattern.
Therefore, the purpose of the work is to deter-
mine, on the basis of the conducted analysis ways
of developing the method of measuring the emission
coeffi cient which would allow conducting research
of structures and materials in a non-destructive way
without the use of additional control samples.
2. Methods and devices for controlling the
emissivity of materials and coatings
2.1. Classifi cation of the methods
The radiation of gray bodies corresponds to the
Stefan-Boltzmann law [7, 8], which establishes the
dependence of the density of integral hemispherical
radiation on temperature:
q = ε σ T4(W/m2), (1)
where: q – density of integrated hemispherical radi-
ation; s = 5.67 × 10-8 (W/m2·K4) Stefan-Boltzmann
constant; ε – emissivity.
For real bodies, the emissivity is a complex func-
tion that depends on the nature of the emitting body, its
temperature, the state of the surface, and for metals –
on the degree of oxidation of this surface. For pure
metals with a polished surface, the emissivity has low
values. At temperatures up to 100 °C, the value of
the emission coeffi cient of the polished metal surface
does not exceed 0.1. With the appearance of oxide
fi lms on the surface of the metal, the emissivity in-
creases sharply and can take values greater than 0.5.
Several methods of experimental determination of
the emissivity are known. They can be divided into
two large groups: optical and thermal.
Among the optical methods, the most widespread
is the spectrometric. The technique of spectrometric
research in determining the spectral curve of specular
refl ection, measured in a wide range of wavelengths
at an angle of incidence of the radiation beam close
to normal. Based on the obtained results, the aver-
age value of the normal and hemispherical emissivity
of the surface is calculated. To implement the spec-
trometric method of measurements, rather complex
and expensive equipment is required, and the result
is obtained by calculations using empirical correction
factors. Thus, this method of measurement is indirect.
Among the thermal methods of experimental
determination of the emissivity, the following have
become widespread: radiation, calorimetric, regular
mode method, and the method of continuous heating
at a constant rate. In all methods, heat transfer due to
convection and thermal conductivity of the air should
be very small compared to radiation.
The radiation method is a relative method [7]. It
is based on a comparison of the radiation of the in-
vestigated body with the radiation of a completely
black or other reference body with a known radia-
tion coeffi cient. For example, a receiving device is
used, in which a diff erential thermocouple is placed.
One of the junctions of the thermocouple receives
radiation from the test body, and the other - from
the surface of the reference body. Based on the mea-
surement result of the thermocouple U-signal, the
emissivity is determined.
The calorimetric method is based on the direct
measurement of the radiation fl ow from the body un-
der study [7]. This method is absolute. The emissivity
is determined based on the Stefan-Boltzmann law.
The method of the regular thermal regime is based
on the laws of the regular thermal regime for a body
whose heat exchange is only radiative [7]. For such
a case, the emissivity is proportional to the cooling
rate, which is determined by the usual method for the
regular regime.
In the method of heating at a constant rate [7], a
sample of the studied material of a simple geomet-
ric shape (for example, a cylinder) is placed inside
a massive cylindrical block, which serves to create
a uniform temperature fi eld around the sample. Heat
exchange between the sample and the block is carried
out only due to thermal radiation. The massive block
is heated so that the heating rate of the sample is con-
stant. The emission coeffi cient is found from the heat
balance equation for the sample, based on the value
of the sample’s heating rate, its heat capacity, and the
emissivity of the massive block.
2.2 Standards in the fi eld of determining the emis-
sivity
The ASTM E408-13 standard [9] defi nes methods
for measuring the total normal emi ssivity of surfaces
using control and measuring devices.
The standard gives the defi nition: Total normal ra-
diation (εN) is defi ned as the ratio of the normal radi-
ation of the sample to the radiation of the black body
at the same temperature. The equation relating εN to
wavelength and spectrally dependent normal radia-
tion [εN(λ)] is:
0 0
, / ,N b N bL T d L T d , (2)
where: Lb (λ,T) = c1· λ
–5 (ec2/ λT –1)–1 – Planck’s black-
body radiation function; с1 = 3.7415 × 10-16 W · m2;
с2 = 1.4388 × 10-2 m · K; Т – absolute temperature;
λ – wavelength; 4
0
,bL T d T .
The E408-13 standard considers in gener-
al terms three diff erent methods of making these
measurements. The fi rst method measures the radi-
ant energy refl ected from the sample (test method
A), the second method measures the radiant energy
55
Overview of materials and coatings emission coefficient control methods
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71)
emitted from the surface of the sample (test method
B), and the third method measures the near-normal
spectral refl ectance (that is, the energy of radiation
refl ected from the sample as a function of wave-
length) and converts this to a total near-normal
emission factor (test method C).
Test method A is best described as a refl ection
method. When the surface is irradiated, the fl ux is
either refl ected, transmitted, or absorbed. The ex-
pression ρ + τ + α = 1 is valid, where ρ is the refl ec-
tivity, τ is the transmission coeffi cient, and α is the
absorption. For opaque surfaces, the transmission
coeffi cient is zero (τ = 0), and the expression reduces
to ρ + α = 1. Kirchhoff ’s law states that for the same
angles and spectral ranges, α = ε. This allows you to
determine from the value of the normal refl ectivity
the value of the normal emission coeffi cient for a
given temperature, or εN = 1 – ρN. At the same time,
the spectral range should be the blackbody range at
this temperature.
The use of test method A imposes two import-
ant requirements on the instruments. The fi rst – the
optical system must measure the refl ection coeffi -
cient in the full hemisphere. The second is that the
spectral characteristic of the device should match
well with the blackbody radiation at this tempera-
ture, which is usually 300 K, but in principle other
temperatures are possible. The standard provides
general requirements for instrumentation of mea-
surements, and one example of such measurements
is discussed in detail in [10].
Method B [9, 11] assumes that the surface under
investigation is placed opposite the hole on the por-
table sensitive element. Radiant energy emitted and
refl ected from the sample passes through the appro-
priate transmission vacuum window and illuminates
the thermal battery. The output signal of the thermal
battery is amplifi ed and fed to the appropriate mea-
suring device. The indicators of the device are rela-
tive and it must be calibrated using standard samples
with a known emission factor.
Method C is based on Fourier transform spectros-
copy (FTIR).
Fourier-transform spectroscopy – a set of meth-
ods of measuring spectra of various nature, in which
the spectrum is calculated not by signal intensity,
as, for example, in prism spectroscopes, but by re-
sponse in the time) or spatial domain (for optical
spectroscopy).
Measurements according to method C can be
carried out using emissometers/refl ectometers
based on FTIR, which determine the refl ection
spectrum with high resolution (ρN (λ)) or (εN (λ)),
in a short period of time. For opaque samples, the
total near-normal emissivity can be expressed as:
0
0
,
1 1 .
,
b N
N N
b
L T d
L T d
(3)
There are many FTIR tools for determining ρN (λ)
and εN (λ) for a large number of wavelength values
of λ. Accordingly, there are various methods for ap-
proximating the above integrals. The most important
feature of any instrument is the ability to collect re-
fl ectance or radiance in the entire hemisphere above
the sample. Some means and methods of their appli-
cation are considered in [12–14].
The standard considers the procedure for imple-
menting each of the methods, the limitations that ex-
ist during measurements, and the main information
that must be indicated in the report.
ISO 9050:2003 [15] standard is used for testing
window and low-emission glass. The measurement
method corresponds to method A of the standard con-
sidered above [9].
The essence of the method is to determine the
specular refl ection curve measured in the wavelength
range of 5 μm – 50 μm at an angle of incidence of the
radiation beam close to normal, and to calculate the
normal emissivity of the surface εn.
Tests are carried out on glass samples of the ac-
cepted batch that do not have defects in appearance.
Glass samples for testing are made in accordance
with the requirements of the operating instructions
for the measuring equipment.
For measurements, a spectrophotometer with a
wavelength range of 5 μ – 50 μm and with an attach-
ment for measuring specular refl ection at an angle of
incidence of light ≤ 20°, with an error of no more than
1% is used.
The test is carried out in accordance with the in-
structions for use of the spectrophotometer, measur-
ing at room temperature (20 ± 5)°C the light refl ec-
tion coeffi cient Ri from the side of the sample with a
low-emission soft coating.
The normal reflection Rn is determined by cal-
culating the mathematical average of 30 values
of the reflection coefficient Ri according to the
formula:
30
1
30
i i
i
n
R
R , (4)
where Ri – coeffi cient of light refl ection; λi – wave-
length.
If the used spectrophotometer has a wavelength
range of up to 25 μm, then the value obtained at a
wavelength of 25 μm is equated to the values of the
56
O. DEKUSHA, S. KOVTUN, Z. BUROVA
ISSN 2786-7102 (Online). Системні дослідження в енергетиці. 2022. 2(71)
spectral refl ectance coeffi cient at a wavelength of
more than 25 μm. At the same time, the approxima-
tion must be specifi ed in the test report.
The normal emissivity εn is determined by the
formula:
1n nR , (5)
where Rn is the normal refl ection.
The emission coeffi cient ε is determined by mul-
tiplying the normal emissivity εn by the coeffi cient A
specifi ed in Table 1.
Table 1. Indicators for determining the emissivity
Normal emissivity εn Coeffi cient А
0.01 1.30
0.02 1.26
0.03 1.22
0.05 1.18
0.1 1.14
0.2 1.10
0.3 1.06
0.4 1.03
0.5 1.00
0.6 0.98
0.7 0.96
0.8 0.95
0.89 0.94
Intermediate values of coeffi cient A are obtained
by linear interpolation.
It is allowed to use other measuring devices that
ensure the determination of the emission coeffi cient
within the limits of the values, with a measurement
error of no more than 2%, certifi ed and verifi ed in the
prescribed manner.
As follows from the given spectrometric meth-
od of measurements, its implementation requires
rather complex and expensive equipment, and the
result is obtained by calculations using empirical
correction factors. Thus, this method of measure-
ment is indirect.
Standard C835-06 [16] defi nes a test method for
determining the full hemispherical emissivity of
surfaces up to 1400 °C. The specifi ed calorimetric
test method covers the determination of the total
hemispherical emission of metal and graphite sur-
faces and coated metal surfaces up to approximate-
ly 1400 °C. The upper temperature of use is limited
only by the characteristics of the sample and the
design limits of the test equipment. The measure-
ments described in this test method are performed
in a vacuum environment.
In general, the device should consist of the fol-
lowing equipment: bell jar, power supply and mul-
timeter for voltage and current measurement, ther-
mocouples and voltmeter or other indicators, vacu-
um system and sample holders. The test scheme is
shown in Fig. 1. Means for electrically heating the
sample shall be provided and instruments necessary
to measure the input electrical power applied to the
sample and the temperatures of the sample and the
surrounding surface. The bell jar should have a black
coating to absorb sample radiation, and the area of
its inner surface should be signifi cantly larger than
the surface area of the sample.
During the tests, the bell jar is vacuumed, an elec-
tric current is passed through the sample, heating it to
a given temperature. After establishing a stationary
thermal regime, determine the power dissipated from
the surface of the sample and the temperature of the
sample and the bell jar.
Based on the assumption that the test sample
is a small emitting body that is surrounded by a
large absorbing surface, the total hemispherical
Fig. 1. Test scheme for C835 [16]
57
Overview of materials and coatings emission coefficient control methods
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71)
emission coefficient of the sample can be calcu-
lated as follows:
4 4
1 1 2
,Q
A T T (6)
where Q – the heat generated in the sample; А1 – sur-
face area of the sample; Т1 and Т2 – temperature of the
surfaces of the sample and the bell jar.
The standard also specifi es the requirements for
the equipment, the sample, the test conditions, and
the content of the report, the factors that can aff ect the
accuracy of the measurements, and the uncertainty
assessment method are specifi ed.
The standard contains references to the original
studies on which this document is based and refer-
ence literature on heat transfer [17–25].
Standard C1371-15 [26] contains a test method
for determining the emissivity of materials using por-
table emissometers at near room temperature. The
test method covers the method of determining the
radiation of opaque and highly thermally conductive
materials using a portable diff erential thermoelectric
emissometer.
The test method given in C1371-15 [26] uses
a differential thermocouple emissometer to mea-
sure total hemispherical emission. The thermal
batteries of the detector are heated to ensure the
necessary temperature difference between the de-
tector and the examined surface. The differential
thermal battery consists of one thermal battery
covered with a black coating and a second battery
covered with a reflective coating. The device is
calibrated using two standard samples, one with a
high emissivity and the other with a low emissiv-
ity, placed on the flat surface of the radiator (heat
sink), as shown in Fig. 2.
The diameter of the measuring head of the emis-
someter is about 50 mm, and the detector elements
are buried about 3 mm into the measuring head.
A sample of the material under examination is
placed on a radiator, and its emissivity is determined
quantitatively by comparison with standard sam-
ples. Calibrations should be performed repeatedly
during the test.
The manufacturer of the emissometer must supply
two sets of standards, each set consisting of a pol-
ished stainless steel (emissivity of about 0.06) and a
black standard (emissivity of about 0.9). The charac-
teristics of the reference samples shall be traceable
to measurements made using an absolute test method
(eg test method C835). It is recommended that one
set be used as working standards and the other set be
used for periodic checks of the emission factor of the
working standards.
The sample of the surface to be tested shall be
carefully selected in such a way as to preserve the
condition of the surface in situ. A sample slightly
larger than the external dimensions of the measuring
head of the emissometer is carefully cut out of the
sample. The thermal resistance of the sample should
not exceed 0.00091 m2 · K/W.
During measurements, the device is turned on and
the head is heated to a temperature 40–60 K high-
Fig. 2. Schematic representation of the thermal part of the emissometer [26] (a) – the measuring head
of the emissometer on the standard with a high emissivity during calibration, the radiator and the cable
of the reading device are also shown; (b) is a bottom view of the measuring head of the emissometer,
showing the elements of the coated thermocouples having high and low emissivity
58
O. DEKUSHA, S. KOVTUN, Z. BUROVA
ISSN 2786-7102 (Online). Системні дослідження в енергетиці. 2022. 2(71)
er than the ambient temperature. The head is placed
over the «black» sample mounted on the heatsink,
and after 90 seconds the output signal voltage Vhi is
measured. The head is then placed over the «light»
sample mounted on the heatsink, and after 90 seconds
the output voltage Vlow is measured. The relationship
between the measured values is valid:
/low low hi hiV V . (7)
The head is placed over the tested sample and af-
ter the signal stabilizes, the Vspec value is measured.
The emissivity of the tested sample is determined by
formula (8):
/spec spec hi hiV V . (8)
The standard specifi es the requirements for the
equipment, the sample, the test conditions and the
content of the report, as well as the factors that can
aff ect the accuracy of the measurements. It is indicat-
ed that the measurement error is usually ±0.02.
In the appendix to the standard, the question of the
infl uence of factors aff ecting the accuracy of deter-
mining the hemispherical measurement coeffi cient is
considered. It was noted that the angle of exposure of
thermal batteries is about 168–169° (approximately
±84° from the normal), that is, less than a full hemi-
sphere. On the other hand, diff erent materials have
signifi cantly diff erent radiation patterns.
2.2 Portable control devices
Portable devices are used, as a rule, to control
characteristics at the temperature of the surrounding
environment, that is, close to room temperature.
In Fig. 3–5 presents the appearance of some por-
table devices, as well as their main technical charac-
teristics and advantages are given (according to the
manufacturers).
Devices & Services Co. model AE1 emissometer
is a specialized device for determining the emission
coeffi cient [27]. The device complies with the C1371-
15 standard discussed above.
The main characteristics and advantages of the
AE1 model emissometer:
− reproducibility (+/– 0.01 emissivity unit);
− it is easy to measure: (detector part of the
device is heated electrically so that the sample does
not need to be heated. No need to measure the tem-
perature);
− fast measurements (after an initial warm-up
period of approximately 30 minutes, emissivity read-
ings can be taken every half minute);
− low cost (devices for comparative measure-
ments cost much more);
− additional adapters (these make measure-
ments in small areas available and special adapt-
ers for samples with irregular surface geome-
tries).
Portable electronic emissometer/reflectometer
TESA 2000 from AZ Technology (USA) [28] is
compact, light, durable and ergonomic, designed
to facilitate use in the field or in the laboratory
to determine the integral emission coefficient at
ambient temperatures. The device can be used in
autonomous mode using battery power. The main
technical characteristics of the device are listed in
Table 2.
The principle of operation of the device is based
on the measurement of the radiation falling on the test
sample and refl ected by the surface of the test sample.
The radiation refl ected from the test sample is collect-
ed by a mirror ellipsoid and directed to the radiation
receiver. At the same time, the surface under investi-
gation is irradiated by a source of thermal radiation
with an emissivity close to the emissivity of a black
body at a temperature of 340 K. The angle of inci-
dence of radiation on the sample under investigation
is 12° to its normal.
Fig. 4. Portable electronic
emissometer/refl ectometer TESA 2000
Fig. 3. Emissometer model AE1 of the fi rm
Devices & Services Co. (D&S) [27]
59
Overview of materials and coatings emission coefficient control methods
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71)
Manual emissometer/refl ectometer ET-100 of
Surface Optics Corporation (USA) [29] measures
the directional refl ectivity in six bands in the ther-
mal infrared spectrum at two sectors of incidence
angles – 20° and 60°. Based on these values, the
directional and integral hemispherical emissivity is
calculated.
The features of the device are the implementation
of refl ection measurement in the infrared spectral
range and the calculation of the directional emissiv-
ity. The measurement is carried out in two sectors of
incidence angles: a sector of 20° near the normal to
the surface and a sector close to 60°, the measurement
time is approximately 10 seconds.
2.3 Stationary control systems
Stationary laboratory systems, as a rule, provide
measurements in a wide temperature range while
evacuating the working chamber to reduce the con-
ductive-convective component of heat exchange. An
example of such an installation, intended for measur-
ing thermoradiation characteristics, is given in [30].
A photo of the working chamber of the installation is
shown in Fig. 6.
a) b)
Fig. 6. Measuring chamber of the emissometer [30]: a) open chamber with the absorber part removed;
b) diagram of the installation used to measure the emis sivity
Table 2. Main technical characteristics of the TESA 2000.
Wavelength from <3μm to >35μm
Accuracy of measurements
(for specular and diff use samples)
± 1% of full scale for gray samples
± 3% of the full scale for non-gray samples
Reproducibility ± 0.5% of full scale or better
Sample temperature environment temperature
Measured quantity
- infrared refl ection
- normal emissivity (300 K)
- hemispherical emissivity (300 K)
Measuring range (refl ection) 0.00 to 1.00
Fig. 5. Manual emissometer/refl ectometer
ET-100 [29]
60
O. DEKUSHA, S. KOVTUN, Z. BUROVA
ISSN 2786-7102 (Online). Системні дослідження в енергетиці. 2022. 2(71)
A cryogenic method for measuring integral
hemispherical emission and absorption coeffi-
cients of various materials at temperatures from
320 K to 20 K is presented. When measuring the
absorption, the temperature of the test sample is
approximately 5 K–35 K. Using a thermal resis-
tance (thermometer), the radiation heat flow be-
tween two flat parallel surfaces in the form of
discs with a diameter of 40 mm, which are placed
in a vacuum, is determined. The test sample and a
reference disc with a surface having known char-
acteristics are immersed in a bath cooled by liq-
uid helium (LHe). The heat flow is measured by
the substitution method, using the thermal power
from an electric heater to calibrate the sensor.
Much attention is paid to the assessment of the
uncertainty of measurements that occurs when
using this method. The capabilities of the device
are demonstrated by measuring the absorption
and emission coeffi cients of a sample of pure alu-
minum. Fig. 7 shows reference samples and their
characteristics.
The expanded uncertainty (k = 2) of the emissiv-
ity measurement ε = 0.0041 measured at ≈30 K for
pure aluminum is less than 11%, and for values of the
emissivity ε> 0.0053 measured at temperatures above
60 K, the uncertainty is lower 7%. The method was
developed primarily for the study of materials with a
low value of the emissivity coeffi cient, such as pure
metals, but the high emissivity of the reference sam-
ple also allows the study of non-metallic materials
with reasonable accuracy.
The Sun LabTek company (India) proposed a
computerized device for measuring the emissivity
[31]. The appearance of the device is shown in
Fig. 8. The experimental unit is based on a metal
sample heated by a concentrated light beam. The
light beam is generated by a continuously ad-
justable halogen lamp and a parabolic reflector.
The reflector concentrates the radiation to a fo-
cal point. The sample is placed on a thermocouple
located at the focal point. The thermal radiation
emitted by the sample is measured by a thermo-
couple. In order to be able to measure radiation at
different distances, the thermal battery is installed
on a movable carriage.
Microprocessor devices are located in a protect-
ed housing. The device is equipped with software to
operate the system and to collect data and training
software. With explanatory texts and illustrations, the
educational software greatly helps to understand the
theoretical principles.
3. Conclusions
Determi nation of the emissivity is relevant for
all cases of research, calculation and modeling of
radiative heat exchange, in particular when deter-
mining the properties of energy-efficient glass and
a) b)
Fig. 7. Reference samples. Temperature dependence of their emission coeffi cient (a) and photograph (b)
of the epoxy sample (upper picture) and the corrugated sample with V-shaped grooves [30]
)) b)
61
Overview of materials and coatings emission coefficient control methods
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71)
Fig. 8. Computerized device for measuring the emissivity «LabTek», India [31]
windows, covering elements of space technology,
when conducting pyrometric and thermal imaging
measurements. Both stationary installations with
a wide range of research temperatures and por-
table express devices for control at temperatures
close to room temperature are used to measure the
emission coefficient.
In stationary systems for measuring the emis-
sivity, which apply thermal methods, heat fluxes
between the object under investigation and some
emitter, as well as the temperature of the struc-
ture elements, are usually determined. But these
methods cannot be used in the control of finished
products.
Portable devices are used for control, but a sig-
nificant disadvantage is the limited temperature
range in which the measurement is performed and
the need to have two standard samples, one with
a high and the other with a low radiation coef-
ficient. A sample of the material under study is
placed on a surface, and its radiation is quantified
by comparing it with the radiation of standards.
For reflectometers the main disadvantage is the
indirect measurements which required the calcu-
lations of the emissivity from the reflection coef-
ficient.
Therefore, it is promising to develop a method for
measuring the emissivity which will non-destructive
and in same do not require additional standard
samples for comparations.
References
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62
O. DEKUSHA, S. KOVTUN, Z. BUROVA
ISSN 2786-7102 (Online). Системні дослідження в енергетиці. 2022. 2(71)
ОГЛЯД МЕТОДІВ КОНТРОЛЮ КОЕФІЦІЄНТА ЕМІСІЇ МАТЕРІАЛІВ ТА
ПОКРИТТІВ
Oлег Декуша1*, к.т.н., ст. досл., https://orcid.org/0000-0003-3836-0485
Світлана Kовтун, д.т.н., ст. досл., https://orcid.org/0000-0002-6596-3460
Зінаїда Бурова2, к.т.н., доцент, https://orcid.org/0000-0002-4712-6298
1Інститут загальної енергетики НАН України, вул. Антоновича, 172, 03150, м. Київ,
Україна;
e-mail: info@ienergy.kiev.ua
2Національний університет біоресурсів і природокористування України, вул. Героїв
Оборони, 15, 03041, м. Київ, Україна;
e-mail: rectorat@nubip.edu.ua
*Corresponding author: olds@ukr.net
Анотація. Коефіцієнт емісії покриття чи матеріалу значною мірою визначає
інтенсивність радіаційного теплообміну на поверхні досліджуваного об’єкта,
9. ASTM E408-13 Standard Test Methods for
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14. Neu, J.T., Dummer, R.S and Myers, O.E. (1987).
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21. Richmond, J.C., and Harrison,W.N. (1960).
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22. Askwyth, W. H., et al. (1959). Interim Final Re-
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63
Overview of materials and coatings emission coefficient control methods
ISSN 2786-7102 (Online). System Research in Energy. 2022. 2(71)
тому його експериментальне визначення важливе для забезпечення необхід-
них теплозахисних характеристик конструкцій. У статті розглядаються
методи контролю коефіцієнту емісії, які регламентуються основними стан-
дартами ASTM E408-13, ISO 9050:2003, C835-06, C1371-15. Методи експе-
риментального визначення коефіцієнту емісії можна розділити на дві великі
групи: оптичні та теплові. Найбільш відомим та розповсюдженим оптичним
методом є спектрометричний. Методика спектрометричного дослідження
полягає у визначенні спектральної кривої дзеркального відбиття, виміряної у
широкому діапазоні довжин хвиль при куті падіння випромінення, близькому
до нормального. За отриманими результатами обчислюють середнє значення
нормальної та напівсферичної випромінювальної здатності поверхні. Серед
теплових методів експериментального визначення коефіцієнта емісії розпо-
всюдження набули: радіаційний, калориметричний, метод регулярного режи-
му, метод неперервного нагріву зі сталою швидкістю. Для вимірювань коефі-
цієнту емісії застосовують як стаціонарні установки з широким діапазоном
температури досліджень, так і переносні експрес-прилади для проведення
контролю за температури, близької до кімнатної. У стаціонарних системах
для вимірювання коефіцієнту емісії, які застосовують теплові методи, за-
звичай визначають теплові потоки між досліджуваним об’єктом та деяким
випромінювачем, а також температури елементів структури. Але ці методи
не можуть бути використані при контролі готових виробів. Тому перспектив-
ним є розробка методу вимірювання коефіцієнта випромінювання, який буде
неруйнівним і при цьому не потребуватиме додаткових стандартних зразків
для порівнянь.
Ключові слова: експрес-контроль, коефіцієнт емісії, емісометри, спектрофо-
тометри, рефлектометри.
Надійшла до редколегіі: 02.11.2022
|
| id | systemreorg-article-615 |
| institution | System Research in Energy |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-19T01:19:22Z |
| publishDate | 2022 |
| publisher | General Energy Institute of the National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | systemreorg/42/652a33c3ef2d91cae32ae972d5d81c42.pdf |
| spelling | systemreorg-article-6152026-07-18T12:57:43Z Overview of materials and coatings emission coefficient control methods Огляд методів контролю коефіцієнта емісії матеріалів та покриттів Dekusha, Oleg Kovtun , Svitlana Burova , Zinaida express control, emissivity, emissometers, spectrophotometers, reflectometers експрес-контроль; коефіцієнт емісії; емісометри; спектрофотометри; рефлектометри The emissivity of a coating and materials determines the intensity of radiation heat exchange on the surface of the object under study. Therefore experimental determination is important to ensure the necessary thermal protection characteristics of structures. The article considers methods of emissivity control, which are currently regulated by the main standards ASTM E408-13, ISO 9050:2003, C835-06, C1371-15. The methods of experimental determination of the emissivity can be divided into two large groups: optical and thermal. Spectrometric is the most widespread optical method. The technique of spectrometric research in determining the curve of specular reflection, measured in a wide range of wavelengths at an angle of incidence of the radiation close to normal. Based on the obtained results, the average value of the normal and hemispherical emissivity of the surface is calculated. Among the thermal methods of experimental determination of the emissivity the following have become widespread: radiation, calorimetric, regular mode method, and the method of continuous heating at a constant rate. The stationary systems with a wide range of research temperatures and portable express devices for control at temperatures close to room temperature are used to measure the emissivity. In stationary systems for measuring the emissivity, which apply thermal methods, heat fluxes between the object under investigation and some emitter, as well as the temperature of the structure elements, are usually determined. But these methods cannot be used in the control of products. Therefore, it is promising to develop a method for measuring the emissivity which will non-destructive and in same do not require additional standard samples for comparations. Коефіцієнт емісії покриття чи матеріалу значною мірою визначає інтенсивність радіаційного теплообміну на поверхні досліджуваного об’єкта, тому його експериментальне визначення важливе для забезпечення необхідних теплозахисних характеристик конструкцій. У статті розглядаються методи контролю коефіцієнту емісії, які регламентуються основними стандартами ASTM E408-13, ISO 9050:2003, C835-06, C1371-15. Методи експериментального визначення коефіцієнту емісії можна розділити на дві великі групи: оптичні та теплові. Найбільш відомим та розповсюдженим оптичним методом є спектрометричний. Методика спектрометричного дослідження полягає у визначенні спектральної кривої дзеркального відбиття, виміряної у широкому діапазоні довжин хвиль при куті падіння випромінення, близькому до нормального. За отриманими результатами обчислюють середнє значення нормальної та напівсферичної випромінювальної здатності поверхні. Серед теплових методів експериментального визначення коефіцієнту емісії розповсюдження набули: радіаційний, калориметричний, метод регулярного режиму, метод неперервного нагріву зі сталою швидкістю. Для вимірювань коефіцієнту емісії застосовують як стаціонарні установки з широким діапазоном температури досліджень, так і переносні експрес-прилади для проведення контролю за температури, близької до кімнатної. У стаціонарних системах для вимірювання коефіцієнту емісії, які застосовують теплові методи, зазвичай визначають теплові потоки між досліджуваним об’єктом та деяким випромінювачем, а також температури елементів структури. Але ці методи не можуть бути використані при контролі готових виробів. Тому перспективним є розробка методу вимірювання коефіцієнта випромінювання, який буде неруйнівним і при цьому не потребуватиме додаткових стандартних зразків для порівнянь. General Energy Institute of the National Academy of Sciences of Ukraine 2022-12-27 Article Article application/pdf https://systemre.org/index.php/journal/article/view/615 10.15407/srenergy2022.02.053 System Research in Energy; No. 2(71) (2022): System Research in Energy; 53-63 Системні дослідження в енергетиці; № 2(71) (2022): Системні дослідження в енергетиці; 53-63 2786-7102 2786-7633 en https://systemre.org/index.php/journal/article/view/615/537 Copyright (c) 2022 Oleg Dekusha, Svitlana Kovtun , Zinaida Burova https://creativecommons.org/publicdomain/zero/1.0 |
| spellingShingle | express control emissivity emissometers spectrophotometers reflectometers Dekusha, Oleg Kovtun , Svitlana Burova , Zinaida Overview of materials and coatings emission coefficient control methods |
| title | Overview of materials and coatings emission coefficient control methods |
| title_alt | Огляд методів контролю коефіцієнта емісії матеріалів та покриттів |
| title_full | Overview of materials and coatings emission coefficient control methods |
| title_fullStr | Overview of materials and coatings emission coefficient control methods |
| title_full_unstemmed | Overview of materials and coatings emission coefficient control methods |
| title_short | Overview of materials and coatings emission coefficient control methods |
| title_sort | overview of materials and coatings emission coefficient control methods |
| topic | express control emissivity emissometers spectrophotometers reflectometers |
| topic_facet | express control emissivity emissometers spectrophotometers reflectometers експрес-контроль коефіцієнт емісії емісометри спектрофотометри рефлектометри |
| url | https://systemre.org/index.php/journal/article/view/615 |
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