Authors:H. Tanaka, S. Sawai, K. Morimoto, and K. Hisano
The hemispherical total emissivity of partially stabilized zirconia has been obtained by a spectral analysis of the normal
emission spectra between 400–850 K. Thermal conductivity was evaluated with this emissivity and temperature gradient in the
sample. Effects of the scattering of the radiation in a ceramic sample are also investigated. In addition, specific heat capacity
was measured by thermal radiation calorimetry. Current results are compared with those reported for tetragonal zirconia with
the same yttria content and for monoclinic phase.
Authors:V. Napp, R. Caps, H.-P. Ebert, and J. Fricke
In order to optimize the infrared extinction of a SiC-powder in a silica powder matrix, Mie scattering calculations for spherical
SiC-particles have been performed. A single oscillator-model was applied to calculate the optical constants of SiC. Taking
into account the particle size distribution of a commercially available SiC-powder, its wavelength dependent extinction coefficient
was calculated. The result is in very good agreement with the extinction spectrum of the powder derived by infrared optically
measurements. Mie scattering theory also was used to find the optimum mean SiC-particle diameter of a mixture of 20% SiC-powder
and 80% silica powder.
The transient hot-wire technique is widely used for absolute measurements
of the thermal conductivity and thermal diffusivity of fluids. It is well
established that fluid radiation effects significantly influence these measurements,
especially those for the thermal diffusivity. Corrections for radiation effects
are based on the models developed and deviations of the measured data from
the ideal line source model. In this paper, the effect of fluid radiation
on the measurements of the thermal conductivity of n-pentane
is presented. For comparison, the influence of thermal radiation effect on
measurement of transparent fluids, such as argon is also shown. The difference
between the influence of natural convection and thermal radiation is also
Authors:F. Tian, L. Sun, J. Venart, R. Prasad, and S. Mojumdar
Various techniques and methodologies of thermal conductivity measurement have been based on the determination of the rate
of directional heat flow through a material having a unit temperature differential between its opposing faces. The constancy
of the rate depends on the material density, its thermal resistance and the heat flow path itself. The last of these variables
contributes most significantly to the true value of steady-state axial and radial heat dissipation depending on the magnitude
of transient thermal diffusivity along these directions. The transient hot-wire technique is broadly used for absolute measurements
of the thermal conductivity of fluids. Refinement of this method has resulted in a capability for accurate and simultaneous
measurement of both thermal conductivity and thermal diffusivity together with the determination of the specific heat. However,
these measurements, especially those for the thermal diffusivity, may be significantly influenced by fluid radiation. Recently
developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. A
thermal conductivity cell for measurement of the thermal properties of electrically conducting fluids has been developed and
Authors:Y. Shi, L. Sun, F. Tian, J. Venart, and R. Prasad
The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity of fluids. Refinement
of this method has resulted in a capability for accurate and simultaneous measurement of both thermal conductivity and thermal
diffusivity together with a determination of the specific heat. However, these measurements, especially those for the thermal
diffusivity, may be significantly influenced by fluid radiation.
The present work investigates the effect of fluid radiation on the measurements of the thermal conductivity of propane. Recently
developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. Measurements
at 372 K with a hot-wire instrument demonstrate the presence of radiation effects in both the liquid and vapor phase. The
influence is much more pronounced in liquid propane at 15.5 MPa than in the vapor phase at 881.5 kPa. The technique employed
to obtain radiation-free thermal conductivity measurements is described.
Thermal insulation and fire protection have been a point of interest and discussion for several decades. Due to its excellent
performances, basalt fiber has been widely used in the fields of thermal insulation and fire protection. The morphological
structure and thermal stability of continuous basalt fiber were analysed using CH-2 projection microscope, scanning electron
microscope (SEM) and thermogravimetry (TG). In order to evaluate the thermal radiation protective performance when exposed
to fire environment, the spectral reflectances of nonwoven fabrics with different thicknesses were evaluated by ultraviolet-visible-near
infrared (UV–Vis–NIR) spectrophotometer analysis. The jointly analysis of TG and UV–Vis–NIR spectrophotometer revealed that
the basalt fiber exhibits good thermal stability, and the nonwoven fabrics present excellent thermal protective performance.
In this article, the theoretical heat transfer of flexible multilayer insulation material which can be used in high (<433 K)
and low temperature (>123 K) environments has been analyzed. A mathematical model has been developed to describe the heat
flux through flexible multilayer insulation material, where the heat transfer consists of thermal radiation, solid spacers
and gas heat transfer. The equations for heat transfer model have been solved by iterative method combining with dichotomy
method using Matlab. Comparison between the experimental results and the calculated values which are obtained from the model
shows that the model is feasible to be applied in practical estimation. The investigation on the flexible multilayer thermal
insulation material will present active instruction to improve the performance and accomplish optimum design of the material.
Authors:J. Durastanti, B. Martin, C. Kneip, and A. Jeanmaire
We show here an adaptation of the classical Flash Method permitting the measure of the thermal conductivity of semi-transparent
porous materials. A flash lamp send a heat pulse on the upper face of a cylindrical sample and lower face temperature is analysed.
The semi-transparent material is sandwiched between two copper slices. The sample used scatters thermal radiation, and absorbs
it very little. It is therefore possible to account for two parts of heat transfer through the material: a pure conductive
phenomenon and a radiative one. In most insulating materials radiative transfer represents about 1/3 of the total heat flux
at the ambiant temperature. The problem is solved with electrical analogy, quadripoles technique and Laplace transform.
The modelization brings out two physical character parameters of the material and a coefficient qualifying the thermal exchange
between the sample and the environment during the experiment.