On Turbulent Pipe Flow With Heat Transfer and Chemical Reaction

Ooms, G.; Groen, G.; Graag, D.P. de; Ballintijn, J.F.

doi:10.1615/ihtc6.1550

Cited by 3 publications

(2 citation statements)

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“…The mean velocity and mean shear stress averaged over one period agree very well with experimental data for a particular choice of the period, which turns out to be quite close to the interval between two successive events of intense turbulent activity in the wall region, the so-called 'bursts' (Laufer & Badri Narayanan 1971). The model, because of its simplicity and modest predictive capability, has proved very popular in diverse applications (see for example Thomas, Chung & Mahaldar 1971;Ooms et al 1978). The model is, however, far too crude to serve the purposes of providing an explanation for the complex processes that take place in the wall region of a turbulent boundary layer, as will be shown later.…”

Section: A C M Begaars I ? Lirishna Prasad and D A De Vriessupporting

confidence: 64%

A structural model for turbulent exchange in boundary layers

1981

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In this paper a model is presented that incorporates characteristic features of the turbulent structures as revealed by recent experimental observations. The principal characteristic features are the occurrence of periodicity and intermittency, not only at the edge of the boundary layer, but also close to the wall.By an averaging procedure, equations are derived for the large-scale part of the turbulent motion. The unknown terms, representing the small-scale turbulent stress, are assumed to be zero except in the so-called burst regions which occupy only a small fraction of the total flow field and arise from local instability of the large-scale flow field. In the model distinction is made between a thin layer near the wall where viscous forces play an important role and the remaining part of the boundary layer where inviscid equations are valid. The momentum transport takes place in three different stages with different mechanisms. First of all the fluid in the wall region is retarded by viscous forces and collected in long narrow regions (streaks). After this a rapid exchange takes place in the burst regions where the low-momentum fluid is ejected into the outer region. Finally the large-scale structures in the outer region take over the transport.It turns out that the transport properties of a turbulent boundary layer can be calculated reasonably well with this deterministic model. It can be concluded that the coherent part of the turbulent motion is very important in the transport process.

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Section: A C M Begaars I ? Lirishna Prasad and D A De Vriessupporting

confidence: 64%

A structural model for turbulent exchange in boundary layers

1981

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“…They found reductions of up to 27%. Ooms et al carried out finite-difference solutions for first-order, irreversible, endothermic reactions in general, using penetration theory, which is of questionable accuracy as a model of the turbulent transport, and thereby determined the enhancement factor for the heat-transfer coefficient as a function of the Reynolds number Re = 2au m ρ / μ , the Prandtl number Pr = c μ/ λ , and the Schmidt number Sc = μ/ ρ D f as well as of three parameters representing the imposed heat flux density at the wall, the rate of reaction, and the heat of reaction.…”

Section: Energetic Effectsmentioning

confidence: 99%

Interaction of Chemical Reactions and Transport. 1. An Overview

Churchill

2005

Ind. Eng. Chem. Res.

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Chemical reactions, fluid mechanics, heat transfer, and mass transfer have both direct and indirect interactions. The direct ones, which are examined here, involve the effects of the fundamental mechanisms of reaction and transport on one another. The indirect ones, which arise from combined reactors, heat exchangers, and separators, are to be examined separately. Although most of the direct interactions have been recognized for decades, the investigations of such phenomena experimentally, theoretically, and numerically are very limited in number and scope. Furthermore, they are scarcely mentioned in textbooks on either chemical reaction engineering or transport. They could readily be incorporated in the software for computer-aided process design but have not, possibly because of the significant added complexity but more likely because of a lack of recognition of their importance or even their existence. In a supplementary investigation, selective numerical calculations have shown that, although the interactions between reaction and transport are of second order in magnitude in some applications, they are critical in others. Accordingly, in another supplementary investigation, new concepts, generalizations, and asymptotes have been devised to encompass these interactions and thereby abet their inclusion in future textbooks and software.

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Compact Heat Exchangers as Chemical Reactors

Churchill¹

2023

Proceeding of Compact Heat Exchangers and Enhancement Technology for the Process Industries - 2003

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On Turbulent Pipe Flow With Heat Transfer and Chemical Reaction

Cited by 3 publications

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A structural model for turbulent exchange in boundary layers

A structural model for turbulent exchange in boundary layers

Interaction of Chemical Reactions and Transport. 1. An Overview

Compact Heat Exchangers as Chemical Reactors

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