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022			_a0017-9310
100			_aMohamed S. El-Genk _9880286
100			_aDasari V. Rao _9880288
245			_aBuoyancy Induced Instability of Laminar Flows in Vertical Annuli—I. Flow Visualization and Heat Transfer Experiments
300			_a2145-2159 p.
520			_aExperiments encompassing both flow visualization and heat transfer measurements (125 < Rein < 1700 and 2.5 × 105 < Grq < 5 × 107) are performed to investigate buoyancy induced instability of developing laminar upflow and downflow of water in a vertical annulus having a diameter ratio of 2.0. The inner wall of the annulus is uniformly heated and the outer wall is insulated. Incipient flow instability is detected from the video images of the dyed flow field, the simultaneous decrease in the temperature difference between the heated wall and the water bulk from its laminar value and the fluctuations in the coolant temperature. The measured values of xfr, based on the video images of the dyed flow fields, are correlated for both buoyancy assisted and opposed flows as functions of local Grashof number, Grq, and local Reynolds number, Re. The Nusselt numbers for buoyancy induced turbulent flows. occurring downstream of the location of incipient instability, are as much as three times higher than those for stable laminar flows at the same inlet Reynolds number, but at lower Grq. The heat transfer data for buoyancy induced turbulent flows are correlated as: Nu = 0.088Raq0.33Rein−0.12, for upflow Nu = 0.21Raq0.29Rein−0.12, for downflow.
650			_aBuoyancy Induced Instability _9880587
650			_aLaminar Flows _9880588
650			_aVertical Annuli _9865363
650			_aFlow Visualization _9116118
773	0		_tInternational Journal of Heat and Mass Transfer _x00179310 _dNew York, U.S.A : Pergamon Subsidiary of Elsevier Science & Technology
856			_uhttps://www.sciencedirect.com/science/article/pii/001793109090116C
942			_2ddc _n0 _cART _o14993 _pMr. Muhammad Rafique Al Haj Rajab Ali (Late)
999			_c814900 _d814900