A formulation for ϵ_M and ϵ_H based on the surface renewal principle

Abstract

To = maximum temperature to which char has been exposed previous to gasification in IGT kinetic scheme 2 Superscript o c = condition in the bulk phase = condition at the core surface = condition at the transition between gasification = condition at the top of the reactor = condition at the gas inlet = condition at the core surface and combustion zone This paper presents a simplified formulation for Elf for low to moderate Prandtl number fluids and for E, , , that utilizes the surface renewal model, but which also accounts for the fact that eddies do not reach the surface. The predicted trend in Prt obtained on the basis of the present analysis suggests an opposite dependency on Pr to that predicted by many of the other analyses.The primary objective of this paper is to demonstrate to turbulence and the classical eddy diffusivity concept. the relationship between the surface renewal approachThe compatibility between these two approaches to turbulence has been previously demonstrated in the context Akron, Ohio.of a comprehensive but complicated surface rejuvenation formulation. A simpler development is presented in this Chemical Engineers.paper for moderate Prandtl numbers (0.5 Pr 5.0)L. C. Thomas is presently on leave from the University of Akron,

Insight into Theories of Heat and Mass Transfer at the Solid−Fluid Interface Using Direct Numerical Simulation and Large Eddy Simulation

“…These models can be broadly classified as the film penetration models, 70,71 growth breakdown models or periodic viscous sublayer models, 20,23,72-74 RSR models, [75][76][77] and surface rejuvenation models. [78][79][80][81][82][83] The details of these models can be obtained from Sideman and Pinczewaski 17 and Thakre and Joshi. 3 4.2.2.…”

“…This "surface rejuvenation concept" formed the basis for the development of several models. [79][80][81][82][83] Harriott 78 proposed a random eddy modification of the penetration theory. He noted that the main error in the previous theories was the assumption that the eddies that influence the transfer rate come all the way to the wall.…”

“…These models, although based on the same concept (random surface renewal, RSR), differ with regard to the assumptions, the near-wall modeling concept, and mathematical formulations. These models can be broadly classified as the film penetration models, , growth breakdown models or periodic viscous sublayer models, ,,− RSR models, − and surface rejuvenation models. − The details of these models can be obtained from Sideman and Pinczewaski 17 and Thakre and Joshi …”

“…He proposed that the fluctuations within the wall region were supposed to be associated with a turbulent burst phenomenon, which is characterized by a mean burst frequency S and a mean distance H from the wall at which fluid is rejected. This “surface rejuvenation concept” formed the basis for the development of several models. − …”

High Temperature Film Formation on Cobalt‐Hardened Gold

“…In a recent paper, the kinetics of cobalt diffusion out of cobalt-hardened gold electroplate was reported (1). In that study, at temperatures above ~150~ in dry air, Auger electron spectroscopy indicated the presence of potassium on the cobalt oxide film surface.…”