MEAN TURBULENCE STRUCTURE IN STRONGLY HEATED AIR FLOWS.

Measurements of mean velocity and mean temperature fields and wall parameters for air flowing in a smooth, vertical tube at low entry Reynolds numbers are presented for heating with constant wall heat flux along the heated length. Two entry Reynolds numbers of approximately 6000 and 4000 were employed with three heating rates, q('+) = q('w'')/ (Gc(,p,i) T(,i)), of approximately 0.0018, 0.0035 and 0.0045. The flow development was measured by obtaining internal profiles along the heated length at axial locations from x/D = 3.17 to x/D = 24.54. An adiabatic entry of 50 diameters preceded the heated region. The three heating rates caused slight, large and severe property variation of the air. The highest heating rate was found to cause significant buoyancy effects. The internal measurements were obtained using constant temperature hot-wire anemometry and resistance thermometry for velocity and temperature, respectively, employing a single short wire probe. The technique developed and employed for the use of a single short hot wire in velocity measurements in non-isothermal flows is presented. The measurements are compared to numerical predictions employing two simple versions of the van Driest mixing length turbulence model. In general, both models agreed with the measurements reasonably well, but for the higher heating rates neither model was completely satisfactory in predicting the velocity profiles. When the buoyancy parameter reached 0.3, the peak velocity occurred in the wall region rather than at the tube centerline. Typically, the Nusselt number was overpredicted by 10% for x/D > 14 and, consequently, the wall temperature was underpredicted by about 7%.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Aerospace and Mechanical Engineering

Grantor dc:publisher

The University of Arizona.

Year dc:date.issued

1984

Author dc:creator

• SHEHATA, AHMED-MOHSEN TAWFICK MOHAMED.

• Temperature control.
• Gas cooled reactors.

Statement dc:rights

• Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10150/187902

OAI identifier oai:identifier

oai:repository.arizona.edu:10150/187902