Zur phänomenologischen Beschreibung der Thermoosmose Überführungswärme und thermomechanischer Homogeneffekt

Abstract

In a membrane separating two identical liquid phases a temperature gradient მT/მx gives rise not only to a flow of heat but also, in general, to a flow of matter. If, conversily, (მT/მx) =0 and liquid is transported through the membrane under a small mechanical pressure difference, heat is liberated or consumed at the surfaces of the membrane. In the thermodynamic theory of irreversible processes these thermomechanical effects are usually treated by considering the membrane simply as a boundary between two homogenous phases. In the present paper it is shown that, by applying the theory of irreversible processes in continuous media, a somewhat more complete description of the thermomechanical phenomena can be achieved. In this treatment the membrane is considered as a separate phase with continuously varying temperature and pressure. This leads at first to the well-known relation between the heat of transfer and the thermomechanical pressure difference which is also obtained in the theory of the discontinuous system. In addition, the existence of a new thermomechanical heat effect can be predicted which occurs in a phase of constant composition in which a temperature gradient მT/მx and a flow of matter (Φm) are simultaneously present. This thermomechanical heat ϰ Φm (მT/მx) is a direct analogue of the Thomson heat of thermoelectricity (i. e. the heat liberated by an electric current in a non-isothermal conductor of constant composition) . It is further shown that a simple relation exists between the coefficient ϰ and the temperature dependence of the heat of transfer.