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【Abstract】

We consider thermoosmosis of a binary fluid mixture, which lies in the one-phase region near the demixing critical point, through a capillary tube, assuming preferential adsorption of one component onto the tube’s wall due to short-range-interactions. On the basis of a coarse-grained free-energy functional, we derive an expression of the thermal force density generated in the adsorption layer by a temperature gradient imposed along the tube. This expression is related to “local excess enthalpy”, as in Derjaguin and Sidorenkov’s formula for conventional thermoosmosis, originally derived for one-component fluids. Our results suggest that, if the mixture is near the upper (lower) consolute point, the flow direction is the same as (opposite to) the temperature gradient.