1,721,032 research outputs found
A critical analysis of the minimum entropy production theorem and its application to heat and fluid flow
No full textWe discuss the principle of minimum entropy production as proposed by Prigogine, providing two examples (heat conduction in a fluid at rest and the combined shear flow and heat conduction in in incompressible fluid) for which the principle produces field equations that do not agree with the balance equations of continuum mechanics. We have not been able to find any special assumption on the temperature dependence oil the phenomenological coefficients (such its thermal conductivity and dynamical viscosity) under which a general agreement between standard balance equations and balance equations determined by the minimum entropy production principle call be stated. A critical analysis of the theorem proof shows that the minimum entropy production of system in a stationary state cannot be different from zer
Intermediate asymptotic behaviour of fluid flows by scale-size analysis
No full textA new approach to the estimation of intermediate asymptotic behaviours of fluid flows is presented. This method is based on a modified dimensional analysis in which fundamental quantities having well-distinguished orders of magnitude are accounted for with different dimensions. Thus, the effects of different physical mechanisms can be isolated inside dimensional equations. The new technique is applied to the analysis of heat and mass transfer correlations for convective flows, and to the interpretation of turbulent drag reduction by additives in wall-bounded flows
Analytical function theory approach to the heat transfer problem of a cylinder in cross-flow at small Peclet numbers
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Geometric approach to laminar convection
No full textThe analytical approach to the solution of a steady-state convection problem for Hagen-Poiseuille flow in tubes of arbitrary cross section was analyzed. The problem was studied in the view of isoperimetric inequalities, that is of inequalities holding for domain functionals, provided that equality is attained. The formal analogy with continuum solid mechanics allowed to develop a semiqualitative theory of laminar convection in tubes of arbitrary cross section. The heat transfer rate per unit length across the wall can be expressed in terms of a geometric parameter for a fluid of constant shear viscosity. The heat transfer rate could be calculated in terms of overall quantities without requiring pointwise solution of the Hagen-Poiseuille problem
Effect of surfactant addition on heat transfer between a flat surface and a liquid impinging jet
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