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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 discussed. [ABSTRACT FROM AUTHOR]

This paper analyses the performance of a counterflow concentric tube heat exchanger and estimates the uncertainties in the temperature response of the heat exchanging fluids caused by uncertainties in their inlet temperatures and overall heat transfer coefficients between the fluid streams. The analysis is based upon the two-point distribution technique. This paper describes the application of this technique to a heat exchanger for which the exact solution for the steady state temperature response is available. Results show that the uncertainty in inlet temperature has a stronger influence. The effect of data uncertainty in heat transfer coefficients, which generally have very high level of uncertainty, have only weak influence. The accuracy of predicted temperature response can, thus, be significantly improved by accurate measurement of the inlet fluid temperatures. [Copyright &y& Elsevier]

The reflection and transmission properties of an anisotropic plasma slab immersed in a static magnetic field normal to the plane of incidence are studied for the case of oblique incidence of a parallel-polarized plane wave. The emphasis is on 'the thin-film reflection properties', namely, the oscillations in the reflection coefficient due to constructive interference of internally reflected waves from the front and back surfaces of the slab geometry. The effect of the slab width, the angle of incidence and the strength of the magnetic field on the nature of the oscillations in the power reflection coefficient are discussed.
The general nature of variation of power reflection coefficient for the slab can be predicted from the nature of the characteristic root q. In the range of real q the power reflection coefficient is oscillatory and the oscillations with increasing amplitude will be more and more crowded as q increases, finally giving rise to an infinite number of oscillations around the point where q is real and infinite. As q approaches asymptotically a value C (C= cos , where is the angle of incidence), the oscillations will be of decreasing amplitude and increasing width. When q equals C the value of is zero. In the range of imaginary q, is non-oscillatory. While in this range, for the semi-infinite case is 1, for the slab is less than 1, showing the tunnelling of power through the slab. approaches 1 as the magnitude of imaginary q approaches infinity. [ABSTRACT FROM AUTHOR]

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