Radiative-conductive heat transfer in temperature-wave conditions

Apparatus for Measuring Thermophysical Properties of Liquids by AC Hot-Wire Techniques

“…The theory governing the method of alternating heating of a cylindrical probe is based on the solution of a problem related to the temperature oscillations of an infinitely long cylindrical conductor of radius ro, placed in an infinite dielectric medium and heated by an alternating current of frequency w. The probe heat balanee equation is similar to that in equation (1) (6) where (d9/dr)lr=ro is the temperature gradient in an adjacent layer. The temperature field 9(r) in a substance is determined by the equation of heat transfer in cylindrical variabIes:…”

“…As in the eas e of a plane probe, equation (6) plays the role of boundary conditions for equation (7). The solution to the proble enables one to establish arelatian between the amplitude and phase of probe temperature oscillations and the thermaI properties of a medium.…”

“…This primarily inftuenees traditional steady-state teehniques involving a plane Iayer and eoaxial eylinders. The analysis of radiation-conductive heat transfer un der eonditions of the periodic heating teehnique (6) shows that the role of radiation heat transfer in thermal conductivity does not exceed the measurement errors up to temperatures of about 600 K. This problem was analyzed(6) for plane temperature waves (a foil probe), whieh form the basis for the measurement technique of thermal aetivity b = .J ACpp, The nonsteady-state linearized equation of radiation-eonduetive heat transfer has been solved by the gray medium approximation. (6) The following simple eonsiderations lead to the conelusions drawn by Kravehun and Phylippov.…”

“…The analysis of radiation-conductive heat transfer un der eonditions of the periodic heating teehnique (6) shows that the role of radiation heat transfer in thermal conductivity does not exceed the measurement errors up to temperatures of about 600 K. This problem was analyzed(6) for plane temperature waves (a foil probe), whieh form the basis for the measurement technique of thermal aetivity b = .J ACpp, The nonsteady-state linearized equation of radiation-eonduetive heat transfer has been solved by the gray medium approximation. (6) The following simple eonsiderations lead to the conelusions drawn by Kravehun and Phylippov. (6) Ifthe amplitude of the probe temperature oscillations equals lOol, the n the amplitude of radiation ftux does not exceed the value qr = 40"n 2 nlool, which corresponds to an absolutely black surface of a probe and a fully transparent medium (where fo is the average probe temperature, n is the refractive index, and 0" is the Stefan-Boltzmann constant).…”