Untitled

A mechanical pressure model equations for a double-membrane system, in which a series of two (Ml and Mr) vertically mounted, flat, symmetric, polymer membranes separate three compartments (l, m, r) containing the heterogeneous non-electrolyte solutions of concentrations , and was developed. These concentrations in initial moment fulfilled the condition > > . The inter-membrane compartment (m) consists of an infinitesimal layer of solution. The volume of the compartments (l, m, r) fulfill the condition Vl = Vr . 170 Vm. The experimental tests were performed for binary (aqueous solutions of glucose or ethanol) or ternary (glucose solutions in 0.75 mol@l!1 solution of ethanol or ethanol solutions in 0.1 mol@l!1 aqueous solution of glucose) solutions. The linear dependencies of the mechanical pressure on the concentration difference in binary solutions and non-linear in ternary solutions were obtained. It is shown that the double-membrane system has amplifying properties of mechanical pressure in the intermembrane compartment of a double-membrane system. The experimental results were interpreted in terms of convective instability, which increases the value of solute permeability coefficients of the system: concentration boundary layer/membrane/ concentration boundary layer.

Inferences for the investigations show that: 1. We have created mechanical pressure model equations for a double-membrane system in which there are series of two, vertically mounted, flat, symmetric, polymer membranes. This model is illustrated by Eqs. (8)–(10). 2. The concentration boundary layers, modifying passive osmotic and diffusive transmembrane transport, is the reason for the reduction of the mechanical pressure in the inter-membrane compartment of a double-membrane system. 3. The field of gravity by generating natural or forced convection flows near membrane regions reduced or eliminated the creation processes of concentration boundary layers, increasing the osmotic and diffusive transmembrane transport and increasing the value of mechanical pressure in the inter-membrane compartment of a double-membrane system. 4. The double-membrane system with membranes oriented in vertical planes is characterized by amplification of hydromechanical pressure. The amplification effect is the result of creation and/or destruction of concentration boundary layers. The effect is a new hydromechanical property in the double-membrane system.