Theory Of Heat Transport Research Articles

Thermal Properties of Hot Filament in Liquid Helium II

Thermal properties of a hot tungsten filament and a gas sheath around the filament in liquid He II were investigated both experimentally and theoretically. It was found that the critical heat power W c above which the gas sheath appears around the wire, can be explained by introducing an effective heat conductivity coming from the Khalatnikov theory. The stability of the gas sheath and its various properties were discussed by extending Knudsen's heat transport theory is gas and the treatment could well explain the experimental results. Frequently, the gas sheath makes an audible hiss and the phenomenon was analysed as an oscillation of the sheath.

Quantum Theory of Heat Transport in an Isotopically Substituted, One-Dimensional, Harmonic Crystal

We present a quantum mechanical treatment of thermal transport in a one-dimensional isotopically substituted harmonic lattice. This work is an extension of a classical mechanical treatment. We find that the difference between the quantum and classical expressions for the thermal conductivity of a random chain vanishes in the limit N → ∞, where N is the number of isotopes. Thus, as in the classical treatment, the thermal conductivity diverges as N1/2. For a periodic diatomic lattice, we derive explicit formulas for the heat current as a function of temperature. At very low temperatures, this quantum mechanical current exhibits Kapitsa behavior.

Thermal Relaxation of Indium Films on Insulating Substrates between 4° and 300°K

The thermal decay times of thin indium films evaporated on sapphire and quartz single-crystal substrates have been measured over a range of temperatures which, with earlier measurements, now extends from 4°–300°K. At the higher temperatures the results were found to be in good qualitative agreement with the predictions of the thermal diffusion theory of heat transport, although there were some quantitative discrepancies. The decay times characterizing the initial part of the thermal decay of a 2200-Å film on a sapphire substrate were measured to be as fast as ∼2×10−9 sec near 100°K, increasing to about 8×10−9 sec at room temperature. The decay times were found to be longest (up to ∼30×10−9 sec) below 10°K, where the heat transport is predominantly by ballistic phonon flow. The decay times for a 2700-Å film on a quartz substrate were found to lie between 13 and 30×10−9 sec in the range of temperatures from 4° to 300°K.

A note on latent heat transport in nucleate boiling

AbstractA simple one‐dimensional transport calculation is made which indicates that latent heat transport, by simultaneous evaporation and condensation at different portions of the bubble surfaces, can account for the major portion of the total heat flux in the neighborhood of the departure from subcooled nucleate boiling (burnout). This differs from the previously held view that the stirring action of the bubbles accounted for most of the heat flow in subcooled nucleate boiling. Other evidence is discussed which favors the latent heat transport theory.