GB/T 36133-2018 PDF English
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Refractory materials -- Determination of thermal conductivity (Platinum resistance thermometer method)
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GB/T 36133-2018: PDF in English (GBT 36133-2018) GB/T 36133-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 81.080
Q 40
Refractory materials - Determination of thermal
conductivity (Platinum resistance thermometer
method)
ISSUED ON: MAY 14, 2018
IMPLEMENTED ON: APRIL 01, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Principle ... 5
4 Equipment ... 5
5 Sample selection and sample preparation ... 9
6 Installation ... 11
7 Test steps ... 11
8 Calculation ... 14
9 Expression of test results ... 17
10 Test report ... 18
Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
Attention is drawn to the possibility that some of the elements of this Standard
may be the subject of patent rights. The issuing authority shall not be held
responsible for identifying any or all such patent rights.
This Standard was proposed by and shall be under the jurisdiction of National
Technical Committee on Refractory Materials of Standardization Administration
of China (SAC/TC 193).
The drafting organizations of this Standard: Wuhan University of Science and
Technology, Yixing Morgan Thermal Ceramics Co., Ltd., Sinosteel Luoyang
Refractory Research Institute Co., Ltd., Hubei Provincial Refractory Product
Quality Supervision and Inspection Station.
Main drafters of this Standard: Yin Yucheng, Li Yiwei, Zhu Qingyou, Yin Bo, Bai
Chen, Liu Zhiqiang, Peng Xigao, Ge Shan.
Refractory materials - Determination of thermal
conductivity (Platinum resistance thermometer
method)
1 Scope
This Standard specifies the principle, equipment, specimen, installation, test
steps, result calculation and test report for determination of thermal conductivity
of refractory materials by platinum resistance thermometer method.
This Standard is applicable to determination of thermal conductivity of refractory
materials that have no carbon, no electrical conductivity and thermal
conductivity is not more than 15W/(m·K).
NOTE 1: The test temperature range of this Standard is from room temperature to 1500°C.
The upper limit of the test temperature also depends on the extreme temperature of the
material or the temperature at which the refractory material becomes a conductor.
NOTE 2: It is generally difficult to obtain accurate test values for heterogeneous materials,
especially for materials containing fibers. When using this method to test these materials,
it needs to be agreed by the relevant parties.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 4513.5, Monolithic (unshaped) refractory products - Part 5: Preparation
and treatment of test pieces
GB/T 5977, Platinum wires for resistance thermometers
GB/T 8170, Rules of rounding off for numerical values & expression and
judgement of limiting values
GB/T 17911, Methods of test for refractory fibre products
GB/T 31057.1, Granular materials - The physical properties - Part 1:
4.1.2 Heating furnace
The heating chamber of the heating furnace shall be able to accommodate two
straight bricks of 230mm×114mm×75mm. Set two support frames at the bottom
to make the test piece evenly heated. The temperature of the heating furnace
at each test temperature point is controlled to ±5°C. The temperature difference
between any two points of the test piece is not more than 10°C. The
temperature shall be stable within 15min before the start of the heating step of
the hot wire. During the constant temperature period, the temperature
fluctuation measured by the thermocouple on the outside of the test piece shall
not exceed ±0.5°C. In addition, four holes shall be set on the furnace wall to
place four hollow alumina protective tubes. Two hot wire heating leads and two
resistance measuring leads are respectively buried in the protection tube. A
certain distance shall be maintained between the holes to reduce the
conductivity during the heating process.
4.1.3 Thermocouple
It is used to measure the temperature outside the test piece. It shall be
composed of platinum or platinum rhodium wire and match the final test
temperature.
4.1.4 Hot wire heating system
The hot wire heating system includes AC power, current divider and breaker.
Generate a stable current of 0A~10A (0V~50V). Hot wire heating shall use
stable alternating current. The test power shall be between 1W/m and 125W/m,
which is equivalent to 0.15W~18.75W of hot wire power between 150mm
resistance measurement leads. The system shall also have a device for
measuring current and voltage drop. Its full-scale accuracy should reach ±0.5%.
4.1.5 Data logging system
Data recording system includes DC power supply, digital voltmeter, program
recorder, relay, current divider. In order to measure the change of the resistance
of the hot wire, a low (such as 100mA) constant DC current needs to be
superimposed on the AC heating current of the hot wire. Record the DC voltage
drop of the hot wire section between the resistance measurement leads to
calculate the temperature change of the hot wire. Because the rate of change
of the hot wire resistance during measurement is only one millionth of its
absolute resistance value, it needs to use a data logging system with sufficient
resolution. The programmed digital voltmeter shall be able to automatically
change the range and automatically calibrate. The digital resolution is
(that is, the accuracy reaches six and a half digits). The sensitivity of the
temperature-time recording equipment shall be at least 0.2µV/mm, or the
5 Sample selection and sample preparation
5.1 Refractory brick
Choose 2 straight bricks with uniform structure and density or specimens of the
same size to form a test piece. The minimum size of a single specimen is
200mm×100mm×50mm. The recommended size is 230mm×114mm×65mm or
230mm×114mm×75mm. The hot wire measuring rack is placed in the center of
two closely contacted specimens. Process a step on the contact surface of the
upper and lower specimens, so as to embed hot wire, as shown in Figure 2.l
In order to ensure that the sample is in close contact with the hot wire, the
maximum height of the specimen step shall not be greater than 0.8mm. Ensure
that its minimum height is not less than the diameter of the hot wire used. In
order to ensure that the test piece does not shake, the average height error of
the two steps shall be within 0.1mm. In addition, the flatness of the upper and
lower specimen contact surfaces shall not be greater than 0.1mm/100mm. After
the steps are processed, put the two specimens together. Make the two steps
coincide with each other. Shake the test piece to detect whether it is shaking. If
it is not shaking, it shall pass the test. After the step height and the flatness of
the close contact surface have reached the requirements, the resistance
measurement lead groove is carved on the step of a specimen. In order to
match the solder joints of the hot wire and the resistance measurement lead,
tools can be used to dig pits at the solder joints for modification.
5.2 Refractory castable
Prepare refractory castable according to GB/T 4513.5. The cast blocks of
refractory castable can be cut into specimens meeting the size requirements
according to 5.1. Or use a special mold to directly form a specimen that meets
the requirements of 5.1. When using a disposable hot wire rack, it can be
poured directly into the test piece.
5.3 Refractory plastic and ramming material
Prepare refractory plastic or refractory ramming material according to GB/T
4513.5. After forming, immediately press the hot wire measuring rack into two
230mm×114mm×65mm or 230mm×114mm×75mm specimens. A certain
pressure shall be applied when drying to make close contact between the
specimens.
5.4 Low-strength materials
Use a notching machine or a knife with a saw blade thickness of not more than
0.5mm to carve a groove for pressing into the hot wire measuring rack on the
230mm×114mm brick surface of one of the specimens.
6 Installation
6.1 Measure the length L of the hot wire between the resistance leads, to the
nearest of 0.5mm.
6.2 Different types of specimens are installed according to the following
methods:
- Specimens that have been prepared as shown in Figure 2: put a specimen
with a lead groove for resistance measurement in the base of the furnace
first; put the hot wire measuring rack into the groove; place another
specimen on the grooved specimen; buckle them together in close contact
with the hot wire;
- Compressible refractory fiber products: through positioning by pillars, install
the first specimen on the lower partition; place the hot wire measuring rack
in its upper center position; place the second specimen on top and place
the partition to make the hot wire measuring rack and the two specimens in
close contact;
- Fine powder and granular material: fill the lower sagger with the powdered
specimen; place the hot wire measuring rack in its center; put the upper
sagger; fill the powder specimen; cover the top cover; measure and record
the mass of the powder specimen in the sagger; calculate its bulk density.
6.3 Place the assembled test piece on the two support racks in the furnace to
ensure uniform heating. Connect the hot wire and resistance lead to the test
circuit respectively. Place the thermocouple for temperature measurement
outside the specimen on the upper part of the center of the specimen. Pull the
excess resistance lead out of the furnace to reduce the length of the inner line.
Make it no more than 200mm. If the resistance measurement lead in the furnace
is too long, when the temperature in the furnace exceeds 1000°C, AC
interference may occur at the heating element.
7 Test steps
7.1 Calibration before test. Depending on the data analysis and calculation
method used, it may be necessary to detect the resistance of the hot wire
measuring rack at 0°C (R0). The hot wire measuring rack can be placed in a
plastic tray containing a mixture of ice and water. Use the same resistance
measurement method as the actual test process to record the data of the four
leads on the hot wire measurement rack. Calculate its freezing point resistance.
Another alternative method is to check the room temperature resistance of the
hot wire measuring rack. Calculate R0 value by RT/R0=(a+bT+cT2). The
resistance (Rs) or specific resistance (RT/R0) and the recorded temperature
data. Obtain the polynomial (a+bT+cT2). The traditional calculation method is
to use the ratio data (RT/R0) of the measured resistance to the freezing point
resistance at 0°C for fitting. R0 shall be measured or calculated when using this
method. Because in the process of repeated use of the hotline, R0 may change
due to stretching or specimen loading steps, it shall regularly use 0°C ice water
bath to verify; or recalculate based on the data measured at room temperature
and the regression coefficient measured in the previous experiment according
to the equation RT/R0=(a+bT+cT2). The advantage of using resistance ratio data
is that the regression coefficients can be normalized. It can be directly
compared with other data sources (for example, different test data measured
by using the same hot wire measuring rack, or test data measured by hot wire
measuring racks of different lengths and wire diameters). Another alternative
method is to only fit the data of the hot wire resistance and temperature. The
advantage of this method is that all data can be obtained in the current test. No
need for 0°C freezing point resistance data R0. There is no need to consider the
slight change in the resistance of the hot wire caused by the hot wire installation
process. Therefore, this method is more suitable for routine tests. But the
disadvantage of this method is that the regression coefficient between
resistance and temperature needs to be obtained through the test heating
process every time. This coefficient will also change due to changes in the
length and diameter of the hot wire rack.
8.3 Slope calculation
Use a suitable linear regression method to calculate the slope (B) from the
linear interval in the RT versus ln(t) curve measured in each test. The linear
interval of RT versus ln(t) curve can be determined by computer analysis
software or visual inspection. In order to avoid the deviation of RT to the high
temperature section when linear regression of the ln(t) curve, it is
recommended to use the ln(t) time axis of uniform interval for analysis. This
may require collecting resistance data over a longer period of time before
performing the linear regression analysis step or collecting more data points at
a uniform sampling rate. If the linear interval is not found on the curve, the
reason may be that the material is not suitable for this test method, or the test
operation has made an error. The test shall be repeated at this time.
8.4 Thermal conductivity calculation
According to the slope (B) of RT to ln(t) based on the data collected during each
heating process of the hot wire and the polynomial regression coefficient
calculated in 8.2, use formula (7) or formula (8) to calculate the thermal
conductivity.
The Fourier heat flow equation for a linear heat source is shown below:
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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