TY - GEN
T1 - Transient stability and convection in impulsively heated porous layers
AU - Kohl, M. J.
AU - Kristofferson, M.
AU - Kulacki, F. A.
N1 - Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2005
Y1 - 2005
N2 - Experiments are reported on initial instability and convection in a porous medium impulsively heated from below. The porous medium comprises either water or a water-glycerin solution and randomly stacked glass spheres in an insulated cylinder of height-to-diameter ratio of 1.9. Heating is accomplished with a constant flux lower surface and a constant temperature upper surface. Results include measurement of the initial transition to convection, overall heat transfer coefficient over a range of Rayleigh-Darcy numbers, and temperature profiles. Time-averaged temperature profiles suggest the existence of a unicellular flow over the range of Rayleigh numbers of the present experiments. The critical Rayleigh number for the onset of convection is obtained in terms of a length scale normalized to the thermal penetration depth as Rac = 83/(1.08η-0.08η2) for 0.02 < η < 0.18. Steady convection in terms of the Nusselt and Rayleigh numbers is represented by a new correlation form, Nu = 0.047 Ra0.91Pr0.11(μ/ μ0)0.72 where Ra is the Rayleigh-Darcy number, 400 < Ra < 5000, and the viscosity ratio is found sufficient to account for strongly temperature-dependent viscosity.
AB - Experiments are reported on initial instability and convection in a porous medium impulsively heated from below. The porous medium comprises either water or a water-glycerin solution and randomly stacked glass spheres in an insulated cylinder of height-to-diameter ratio of 1.9. Heating is accomplished with a constant flux lower surface and a constant temperature upper surface. Results include measurement of the initial transition to convection, overall heat transfer coefficient over a range of Rayleigh-Darcy numbers, and temperature profiles. Time-averaged temperature profiles suggest the existence of a unicellular flow over the range of Rayleigh numbers of the present experiments. The critical Rayleigh number for the onset of convection is obtained in terms of a length scale normalized to the thermal penetration depth as Rac = 83/(1.08η-0.08η2) for 0.02 < η < 0.18. Steady convection in terms of the Nusselt and Rayleigh numbers is represented by a new correlation form, Nu = 0.047 Ra0.91Pr0.11(μ/ μ0)0.72 where Ra is the Rayleigh-Darcy number, 400 < Ra < 5000, and the viscosity ratio is found sufficient to account for strongly temperature-dependent viscosity.
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U2 - 10.1115/HT2005-72023
DO - 10.1115/HT2005-72023
M3 - Conference contribution
AN - SCOPUS:29744432919
SN - 0791847314
SN - 9780791847312
T3 - Proceedings of the ASME Summer Heat Transfer Conference
SP - 235
EP - 242
BT - Proceedings of the ASME Summer Heat Transfer Conference, HT 2005
T2 - 2005 ASME Summer Heat Transfer Conference, HT 2005
Y2 - 17 July 2005 through 22 July 2005
ER -