Persistent Link:
http://hdl.handle.net/10150/187902
Title:
MEAN TURBULENCE STRUCTURE IN STRONGLY HEATED AIR FLOWS.
Author:
SHEHATA, AHMED-MOHSEN TAWFICK MOHAMED.
Issue Date:
1984
Publisher:
The University of Arizona.
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.
Abstract:
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%.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Temperature control.; Gas cooled reactors.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Aerospace and Mechanical Engineering; Graduate College
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMEAN TURBULENCE STRUCTURE IN STRONGLY HEATED AIR FLOWS.en_US
dc.creatorSHEHATA, AHMED-MOHSEN TAWFICK MOHAMED.en_US
dc.contributor.authorSHEHATA, AHMED-MOHSEN TAWFICK MOHAMED.en_US
dc.date.issued1984en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © 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.en_US
dc.description.abstractMeasurements 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%.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectTemperature control.en_US
dc.subjectGas cooled reactors.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAerospace and Mechanical Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.identifier.proquest8510896en_US
dc.identifier.oclc693601517en_US
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