Turbulent flow combined convection

Specific correlations of individual film coefficients necessarily are restricted in scope. Among the distinctions that are made are those of geometry, whether inside or outside of tubes for instance, or the shapes of the heat transfer surfaces free or forced convection laminar or turbulent flow liquids, gases, liquid metals, non-Newtonian fluids pure substances or mixtures completely or partially condensable air, water, refrigerants, or other specific substances fluidized or fixed particles combined convection and radiation and others. In spite of such qualifications, it should be... 

The theoretical results that have been discussed here allow k to be of order unity, a condition that sometimes has been referred to as one of strong strain, although the term moderate strain seems better, with strong strain reserved for large values of k. Small values of k are identified as conditions of weak strain under these conditions the reaction sheet remains far to the reactant side of the stagnation point, and by integrating across the convective-diffusive zone, a formulation in terms of the location of the reaction sheet can be derived [102], like that discussed at the end of Section 9.5.1. By combining the approximations of weak strain and weak curvature, convenient approaches to analyses of wrinkled flames in turbulent flows can be obtained [38]. 

Heat delivery. Convection and conduction from hot gas sweeping by is the leading mode of heat transfer to a drying coating to supply the latent heat of vaporization of solvent. Except when solvent evaporation is so very rapid as to produce an appreciable convective velocity away from the surface, in turbulent gas flow the mechanisms of heat transfer to and solvent transfer away from the evaporating surface are virtually identical combinations of convective action with thermal conduction on the one hand and molecular diffusion on the other. This is reflected in useful correlations, like Colburn s, of the mass transfer coefficient with the more easily measured heat transfer coefficient in turbulent flow. It is also the reason that the now fairly extensive literature on the performance and design of driers focuses on heat transfer coefficients and heat delivery rates. 

Adverse hydraulic conditions of settling such as turbulence, convective flows, mixing, etc. represent negative influences on emulsion separation. Significant improvement of separation efficiency for petroleum emulsions is achieved by the use of gravitational settling in combination with thermal, chemical and electrical methods. 

The tube is packed with catalyst pellets. Flow may be either laminar or turbulent. The velocity profile is assumed to be flat. Transfer of heat and mass in the radial direction is modeled using empirical diffusion coefficients that combine the effects of convection and true diffusion in the radial direction. There is no axial diffusion. Details are given in Chapter 9. This model is important only for nonisothermai reactors. It reduces to piston flow if the reaction is isothermal. 

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