ABSTRACT
The basic thermodynamic notions address essentially pure substances and mixtures of fluids, which are in the realm of chemical engineering, e.g., the comprehensive introduction of Smith et al. An open system exchanges mass, momentum, energy and/or entropy with the surroundings, while a closed system does not. In practice, an open system can be made closed by including the sources with which the exchanges take place. Stability of equilibrium provides another argument against the existence of a fluid which would be incompressible but thermally dilatable. Thermal equilibrium may be reached if the membrane is a thermal conductor. Similarly, chemical equilibrium can be realized only if the membrane is permeable to the fluid.
