Journal of Fluid Mechanics

Thermal transpiration in a circular capillary with a small temperature difference

B. T.  Porodnov a1, A. N.  Kulev a1 and F. T.  Tuchvetov a1
a1 Urals Polytechnical Institute, 620002 Sverdlovsk K-2, USSR

Article author query
porodnov bt   [Google Scholar] 
kulev an   [Google Scholar] 
tuchvetov ft   [Google Scholar] 


The results of an experimental investigation of the thermal transpiration effect (the thermomolecular pressure difference or t.p.d. effect) in a single glass capillary with a length-to-radius ratio of 250 are presented. The temperatures of the gas in the ‘cold’ and ‘hot’ chambers were 273·2°K and 293°K, respectively. A modified relative method has been used. To measure the t.p.d. effect, a capacitance differential digital micromanometer with sensitivity 4·5 × 10−5N/(m2Hz) was used. The gases investigated were He, Ne, Ar, Xe, H2, D2, N2, CO2, CH4 and SF6. It was discovered that in the intermediate flow regime the thermal-creep flow rate does not depend on the (non-isothermal) tangential momentum accommodation coefficient. From the experimental data on the viscous slip flow regime, the Eucken factors and the accommodation coefficients are calculated. For inert gases the Eucken factor is found to be equal to 2·5 within the experimental error, while the accommodation coefficients differ significantly from unity.

(Published Online April 19 2006)
(Received August 25 1977)