energies Article Neoclassical Navier–Stokes Equations Considering the Gyftopoulos–Beretta Exposition of Thermodynamics Janusz Badur 1, Michel Feidt 2 and Paweł Ziółkowski 3,* 1 Energy Conversion Department, Institute of Fluid Flow Machinery, Polish Academy of Science, Fiszera 14, 80-952 Gda´nsk,Poland;
[email protected] 2 Laboratory of Energetics & Theoretical & Applied Mechanics (LEMTA), University of Lorraine, 2 Avenue de la Forêt de Haye, 54518 Vandœuvre-lès-Nancy, France;
[email protected] 3 Faculty of Mechanical Engineering, Department of Energy and Industrial Apparatus, Gda´nskUniversity of Technology, Narutowicza 11/12, 80-233 Gda´nsk,Poland * Correspondence:
[email protected]; Tel.: +48-58-347-2073 Received: 14 February 2020; Accepted: 25 March 2020; Published: 2 April 2020 Abstract: The seminal Navier–Stokes equations were stated even before the creation of the foundations of thermodynamics and its first and second laws. There is a widespread opinion in the literature on thermodynamic cycles that the Navier–Stokes equations cannot be taken as a thermodynamically correct model of a local “working fluid”, which would be able to describe the conversion of “heating” into “working” (Carnot’s type cycles) and vice versa (Afanasjeva’s type cycles). Also, it is overall doubtful that “cycle work is converted into cycle heat” or vice versa. The underlying reason for this situation is that the Navier–Stokes equations come from a time when thermodynamic concepts such as “internal energy” were still poorly understood. Therefore, this paper presents a new exposition of thermodynamically consistent Navier–Stokes equations. Following that line of reasoning—and following Gyftopoulos and Beretta’s exposition of thermodynamics—we introduce the basic concepts of thermodynamics such as “heating” and “working” fluxes.