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A Study on the Mechanism of Molecular Transport with Systems of Gaseous Paraffins and of Convective Transport from Single Cylinders, Single Spheres, and Arrays of Spheres into Turbulently Flowing Streams

Citation

Galloway, Terry Randolph (1967) A Study on the Mechanism of Molecular Transport with Systems of Gaseous Paraffins and of Convective Transport from Single Cylinders, Single Spheres, and Arrays of Spheres into Turbulently Flowing Streams. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09182002-074117

Abstract

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PART I

Intermolecular pair potential functions for the Leonard-Jones [infinity]-6, 12-6, and 9-6 form, and of the three parameter forms of Morse and of Kihara for a spherical core, were used to fit new gas phase viscosity data at low pressure for the normal paraffins through n-decane. The intermolecular force parameters were obtained and found to be unique for the Morse and Kihara potentials. All potential models underestimated the temperature dependence of the viscosity, but the Kihara was found to be superior with deviations of several percent.

The Eucken relation for predicting the gas phase thermal conductivities of gaseous paraffins at low pressure proved to 18% low. Configurational thermal conductivities were calculated from experimental data, and a new form of conductivity excess above the configurational value was developed which produced a quantitative relationship to the heat capacity excess. This relation was compared with a number of theories and found to be in agreement, and it predicted the paraffin data within 4.9%.

Binary diffusion coefficient data were compiled and found to be in agreement with theoretical predictions, within the large experimental uncertainties associated with the data. Existing methods of prediction of viscosity and conductivity for binary mixtures of similar species were found to be inadequate for dissimilar systems and a more adequate but simple theoretical relation was shown to apply. Also the importance of the dense gas corrections involved in high pressure gas phase viscosities and conductivities are discussed.

PART II

Similarity solutions of the Blasius form to the problem of flow around a circular cylinder and sphere at moderately high Reynolds numbers were obtained for the general case of variable Prandtl (or Schmidt) groups. A dimensionless ratio referred to as the [Froessling] group" was obtained from these solutions which proved to be most useful in understanding the mechanism of transport from bluff bodies into turbulently flowing streams and into separated wake-flows. Quantitive experimental results were obtained for the influence of the level of turbulence in the main stream and effects of separation on the convective heat and mass transfer from cylinders and spheres. The Reynolds number was varied from 2,600 to 86,000 and free-stream turbulence from 0.013 to 0.25. These results were correlated in terms of the [Froessling] group and compared with available experimental data within 7.7% for cylinders and 8.8% for spheres.

The local [Froessling] group was found to be proportional to the product of the turbulence level and the square root of the Reynolds number in the laminar flow region and increased strongly with Reynolds number in the wake. The local effects of turbulence were uniform from 35% increases at the forward stagnation. The point of separation was strongly delayed by turbulence. The transition to supercritical flow was established from the heat transfer measurements and found to agree with drag measurements. The local pressure coefficient was measured with a small pitot tube in the surface, and remained as unity at the forward stagnation point, independent of turbulence variations, and was altered only slightly near and following separation by varying Reynolds number and turbulence during subcritical conditions. The dependence of the position of separation upon Reynolds number and free-stream turbulence level was established quantitatively.

PART III

The mechanism of local transport in regular packed arrays of uniform spheres was studied in the light of boundary layer theory and the established behavior from bluff bodies. Local measurements were made with a movable calorimeter on the surface of a sphere placed in a rhombohedral No. 6 array. The effective local velocity and turbulence level within the array were determined. This model was found to predict available data in packed, distended, and fluidized beds of all shaped particles within 9.8%, and 12% for columns irrigated with liquid.

Electrostatic reproductions of photography on pp. 132,136, 220-221, 297-299, 308, 310, 368, 374, 376, 379, and 388 are not adequate.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Sage, Bruce H.
Thesis Committee:
  • Unknown, Unknown
Defense Date:7 March 1967
Record Number:CaltechETD:etd-09182002-074117
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-09182002-074117
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3603
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:18 Sep 2002
Last Modified:26 Dec 2012 03:01

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