The effective viscosity of a turbulently suspended fluid‐particle mixture

The distinctly different turbulent heat transfer characteristics of flocculated kaolin slurries are compared with nonflocculated coal slurries via modified J‐factor correlation forms for tubular exchangers. Both slurry types were statistically best‐fitted with the approximate solution Bingham plastic flow model in preference to the local shear power law. In addition, the first known turbulent slurry heat transfer cooling results are presented along with the heating results. No distinction was made between heating and cooling correlation forms because of a random scatter of experimental points. Experimental results were interpreted as follows A. Flocculated kaolin slurries JH = (h/CpG) (C pμLe Bϕ/K1)2;3= 0.027(DVρ/μLeBϕ)0.2 11%ω < %ω Solids < 24%ω Maximum Deviations: + 19.3%, − 17.8% B. Non‐flocculated coal slurries Jw = (h/CpG)(CpμLeBϕ/kw)2/3e−Bϕ/4) =0.0285 (DVρ/ μLeBϕ)−0.2 13%w > %w Solids < 33.5%. Maximum Deviations: + 17.8%, ‐ 11.1%

Section: Slurry Data Treatment Mul Resultsmentioning

confidence: 99%

Heating and cooling of flocculated and non‐flocculated slurries in tubular heat exchangers

Crewe

Simons

1973

“…The contact load is responsible for the excess hydraulic gradient, found in this flow regime'8*g', and the question arises as to whether the macroturbulent effects played any part in the enhancement of the previously reported mass transfer rates'*'. The evidence from heat transfer studies in slurries""' suggests that they do not; however because of the above complications in horizontal lines it was decided to study the mass transfer process in a vertical line where the radial concentration and velocity gradients are uniform and of course the solids On a inesurk les taux de transfert de masse de I'oxyghe dissoos, par les parois, dans un tube vertical dont le diamktre interne Ctait de 5 centim&tres et qui transportait, sous forme de suspensions aqueltses de 5, 10 a r e fully suspended with an absence of macroturbulence effects. As well as giving information about the effects of fully suspended particles on the boundary layers, it was also considered that these experiments would help to clarify the previous results obtained for horizontal flow.…”

mentioning

confidence: 99%

Wall mass transfer in vertical and horizontal slurry pipelines

Postlethwaite

Holdner

1976

Wall mass transfer rates of dissolved oxygen have been measured in a vertical pipe, 5 cm. I.D., carrying aqueous slurries of 5, 10, and 15 vol%, 60–100 and 30–50 mesh sands at velocities in the range 1.2 to 3.35 m/s. The results show increases of up to 100% over those found with water, with the effect of the solids increasing with decreasing particle size and increasing with increasing concentration. The jD factors decreased linearly with increasing Res, unlike the previous results with horizontal pipes where maxima were found relating to vertical concentration gradients.

Wall mass transfer in horizontal slurry pipelines

Postlethwaite

Holdner

1975

Measurements have been made of the rate of mass transfer of dissolved oxygen to the walls of 5 cm diameter horizontal pipes carrying aqueous slurries of sand and iron ore, in the concentration range 10 — 20 vol % at velocities up to twice the critical value for deposition. The results which show that the suspended particles greatly increase the rate of mass transfer are discussed in terms of the analogies and are compared with the results of previous workers for heat and momentum transfer. In the case of mass transfer in systems with high Schmidt numbers it appears that there is a specific effect of the solid particles relating to the disruption of the viscous sub‐layer.