EXPERIMENTAL STUDY OF THE THERMAL CONDUCTIVITY OF HEAT
INSULATION MATERIALS BASED ON EXPANDED VERMICULITE
V. É. Peletskii
and B. A. Shur
Translated from Novye Ogneupory, No. 11, pp. 41 – 43, November 2007.
Original article submitted July 13, 2007.
Results are presented for experimental studies of the thermal conductivity of expanded vermiculite. Tests are
performed in an experimental test unit by a steady-state heat flux. Thermal studies are carried out in the range
300 – 1100 K. It is shown that thermal conductivity increases uniformly with an increase in temperature.
The most probable reason for an increase in thermal conductivity is the effect of heat radiation. Results are
provided for an approximate second power polynomial.
The properties of heat insulation materials have been
studied for many decades. The results of studies may be
found in publications on power generation , and in special
monograms [2, 3] devoted to the technique of an appropriate
experiment and analysis of features of heat transfer in mate-
rials used for heat protection of structures and equipment.
However, every time when material scientists change the
technology for preparing or modifying a material composi-
tion , a requirement arises for a new approach to an exper
iment in order to obtain information about the action of these
changes on material properties. This becomes particularly
important when we are talking about increased temperature
and about operation of materials in corrosive media. An im
portant characteristic of heat insulation is the thermal con
ductivity coefficient (TCC). Information about its depend
ence on temperature is used in numerical analysis of the effi
ciency of heat protection with the action of a flame on a
structure. Results are presented in this article for studying the
thermal conductivity of insulation based on vermiculite, i.e. a
natural composite of refractory oxides.
AND EXPERIMENTAL DEVICE
In order to measure TCC a method of steady-state heat
flux in a plate was selected. Under conditions of direct mea
surement of heat capacity, directed at a specimen, it relates to
a class of the so-called absolute methods not requiring use of
reference specimens. The basis of the method is solution of a
boundary problem for thermal conductivity l foraun-
idimensional steady-state problem without internal sources
of heat release.
The differential equation
div(l gradT )=0 (1)
is resolved here with boundary conditions of the first order:
x =0,T = T
x = L, T = T
are temperatures of the boundary surfaces of
In an approximation for constant thermal conductivity
solution of the problem leads to a calculation equation of the
where W is heat capacity transferred through a specimen
from a heater to a cooler; L is specimen thickness; S is speci
men cross sectional area.
The value for thermal conductivity calculated by Eq. (3)
traditionally relates to and average specimen temperature.
Under conditions when the “cold” plane of specimen during
Refractories and Industrial Ceramics Vol. 48, No. 5, 2007
1083-4877/07/4805-0356 © 2007 Springer Science+Business Media, Inc.
Institute of Thermophysics of Extreme Conditions of Joint Institute
of High Temperatures, Russian Academy of Sciences, Russia.