The nature of thermophoresis of highly heat-conducting bodies in gases

✍ Scribed by S.P Bakanov

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 343 KB
• Volume: 68
• Category: Article
• ISSN: 0021-8928
• DOI: 10.1016/s0021-8928(04)90002-0

✦ Synopsis

A method of calculating the rate of thermophoresis of large bodies in gases is briefly described. Particular attention is devoted to the features of the mechanism of the thermophoresis of highly heat-conducting bodies, which were subject to the attempts made over many years to explain the anomalies. A qualitative explanation of the mechanism is given. It is shown that it owes its origin to the presence in the gas region, close to the body surface, of a second (mixed) derivative with respect to the temperature (whereas Epshtein-Maxwell thermophoresis is due to its first derivative). It is emphasized that, whereas classical thermophoresis is independent of the Knudsen number Kn = k/R (k is the mean free path of the gas molecules and R is a characteristic dimension of the body), the rate of thermophoresis of highly heat-conducting bodies is directly proportional to it. On the other hand, classical thermophoresis depends very much on the ratio of the thermal conductivities of the body and the gas, while the rate of thermophoresis of highly heat-conducting bodies is independent of this ratio. It is shown that reliable quantitative results can be obtained only if reliable data is available on the accommodation coefficients for collisions between the gas molecules and the body surface.