A STUDY OF HEAT CONDUCTION
IN STRUCTURAL CERAMIC MATERIALS.
PART V. THERMAL CONDUCTIVITY OF CERAMICS BASED ON MgO
R. I. Abraitis,
A. K. Dargis,
A. A. Rusyatskas,
and É. J. Sakalauskas
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 12, pp. 41 – 45, December, 2000.
The results of an experimental study are presented and the effectiveness of the earlier described methods is an
alyzed. The thermal conductivity of one and the same specimen is studied in a gas-dynamic bench and in an
optical furnace in order to estimate the accuracy of the determination of systematic errors of the methods. The
effect of various heat loads is determined. A comparison of the data shows that the algorithm of descriptive
regularization makes it possible to reduce the effect of systematic errors on the thermal conductivity of a MgO
material from 40 to 7% at the cold end and from 7 to 3% at the hot end. The residual scattering of individual
curves does not exceed the range of the instrumental error of measurement, and the standard deviations reflect
its value. The random nature of the residual scattering proves the earlier drawn conclusion that the effective
thermal conductivity is independent of the density of the heat flow measured within 482 – 691 kW/m
rate to 15%.
The considered instrumental errors in measurement of
heat flows and temperature distribution appear because of
the inaccuracy of the gauges and devices used for detecting
the measured signals. However, if the measurement devices
are well chosen with respect to their sensitivity, these errors
can be diminished considerably. Extensive experimental
practice has shown that the main role in high-temperature
measurements is played by systematic errors of the method,
which can be estimated and decreased only by additional
measurements for standard specimens.
At the present time, we do not possess ceramic high-tem
perature certified standard specimens for determining the
thermal conductivity at up to 2000 K. Therefore, we tested
the method in question by performing a physical experiment
for a ceramic specimen the thermophysical properties of
which had been studied by a nonstationary hot-wire method.
The chemical composition of the material of the specimen
included 93.3% MgO, 1.8% CaO, 1.9% SiO
, and 3.0%
. The apparent density and the porosity were
and 5%, respectively. The thermal conductivity
in W/(m × K) was 8.93 – 10.5 for 673 K, 5.66 – 6.64 for
1073 K, and 4.17 – 4.88 for 1473 K. The values of the ther
mal conductivity of the material based on MgO were evalu
ated with an error of 10% at a confidence probability of 0.95.
The same material was used to fabricate the blocks of the
side calorimeter, which were later used for studying the ther
mal conductivity of other materials.
In order to estimate the accuracy of the determination of
systematic methodological errors, we studied the thermal
conductivity of the same specimen in a gas-dynamic bench
and in an optical furnace. The measurements were made at
different heat loads so that the pairs of temperature drops ob
tained in both installations were close to each other (Fig. 10
and Table 3). This measurement technique allowed us
– to establish the heat leakage through the side surface of
a specimen and to evaluate the accuracy of its determination;
– to determine the effect of systematic errors of measure
ment of the longitudinal profile of the temperature on the de
pendence of the thermal conductivity;
– to estimate the effect of different heat loads on the ef
fective thermal conductivity of the studied material.
Refractories and Industrial Ceramics Vol. 41, Nos. 11 – 12, 2000
1083-4877/00/1112-0453$25.00 © 2001 Plenum Publishing Corporation
For the beginning of the article, see No. 8 of 1999; for the conti
nuation, see Nos. 2, 4, and 10 of 2000.
Institute for Architecture and Construction Engineering of Lithu