Developments and Status of NET

Non-equilibrium thermodynamics was founded by Onsager. The theory was further elaborated by de Groot and Mazur and Prigogine. The theory is based on the hypothesis of local equilibrium a volume element in a non-equilibrium system is in local equilibrium when the normal thermodynamic relations apply to the element. Evidence is emerging that show that many systems of interest in the process industry are in local equilibrium by this criterion. Onsager prescribed that each flux be connected to its conjugate force via the extensive variable that defines the flux. -  

Onsager assumed that the variables and the rate laws were the same on the macroscopic and the microscopic level this is the so-called regression hypothesis. Also using the assumption of microscopic reversibility, he proved the reciprocal relations  

These assumptions restrict the validity of NET, but as stated above, they have a wide range of validity. It has long been known that the Navier-Stokes equations are contained in NET. More recently, NET has been extended to deal with transport across surfaces, quantum mechanical systems, and mesoscopic systems see Chapter 2. We have chosen to illustrate NET with cases of transport through surfaces in the following sections. 

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