Flow reversal of laminar mixed convection in the entry region of symmetrically heated, vertical plate channels

Desrayaud, Gilles; Lauriat, Guy

doi:10.1016/j.ijthermalsci.2009.03.002

Cited by 55 publications

(30 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar result of the axial velocity profile is found in the literature by Desrayaud and Lauriat. [23], for the dimensionless coordinate Z= 20 and Ω= 530, which is comparable to the obtained profile in the current paper for Z= 29 and Ω= 600. . Re=100, Ω= 1000 Figure 11 presents the contour lines of the axial velocity distribution at the cross-section surface (z= 29 cm) for the selected values of the buoyancy parameter Ω, which is computed at the same Reynolds number Re = 100.…”

Section: Dynamic Effectsupporting

confidence: 91%

Numerical Analysis of the Parameters Governing 3D Laminar Mixed Convection Flow in a Rectangular Channel with Imposed Wall Flux Density

Aidaoui¹,

Lasbet²,

Loubar³

2016

IJHT

View full text Add to dashboard Cite

A numerical study is carried out in order to understand the effect of the parameters governing three dimensional (3D) laminar mixed convection flows in a rectangular channel with imposed wall flux density. The mixed convection can be governed and influenced by many factors which appear in the conservation equations. In the literature, no unanimity is found on the formulation of these parameters which can affect the bouncy forces in the motion equation, and consequently the onset of the mixed convection regime, the Nusselt number and the Poiseuille number. The principal result of this paper illustrates that the main factor characterizing the heat and flow regime of the mixed convection is the ratio between the Grashof number Gr, and the Reynolds number Re instead of the Richardson number Gr/Re 2 . Obtained results demonstrate as well the influence of the buoyancy parameter and Richardson number on the magnitude of the distortion of the flow velocity and therefore the flow structure.

show abstract

Section: Dynamic Effectsupporting

confidence: 91%

Numerical Analysis of the Parameters Governing 3D Laminar Mixed Convection Flow in a Rectangular Channel with Imposed Wall Flux Density

Aidaoui¹,

Lasbet²,

Loubar³

2016

IJHT

View full text Add to dashboard Cite

show abstract

“…3 shows another view of the results linked to a fixed flow rate smaller than the natural inlet flow rate. For this case, we consider a channel height H = 1.5 m and a channel width D = 3 cm in order to check that the present results are in full agreement with those published in [2][3][4]. Figure 3 raises obviously the question of the origin of existence of flow recirculations within the entry region for aiding mixed convection in vertical channels.…”

Section: Constant Flow Ratesupporting

confidence: 67%

“…The influence of the dynamical boundary conditions at the inlet and outlet sections is discussed by considering air entering at T 0 = 300 K into a vertical channel with height walls H = 1 m at uniform hot temperature T h = 320 K (or H = 1.5 m, just for allowing comparisons with previously published works [2,3]). The channel width was D = 2 cm or D = 3 cm.…”

Section: Resultsmentioning

confidence: 99%

“…upward flows with heating or downward flows with cooling. Under these conditions, the axial velocities may increase near the channel walls and decrease within the core region, with possible occurrence of a flow recirculation in the entry region for large effects of the buoyancy force [1][2][3][4] (not to be confused with flow reversal occurring close to the outlet section in asymmetrically heated channels [5][6][7][8][9][10]). In these cases, it is generally expected that heat transfer for mixed convection is larger than for forced convection.…”

Section: List Of Symbols Amentioning

confidence: 99%

“…It follows that the problem formulation depends on four parameters: 3 and Pr ¼ m 0 =a 0 ; the channel aspect ratio, the Reynolds, Grashof and Prandtl numbers, respectively. The relative strength of the buoyancy force is then characterized either by the Richardson number, Ri ¼ Gr=Re 2 ; for the first set of dimensionless variables or by the product Ri Â Re ¼ Gr=Re for the second set.…”

Section: Boundary and Initial Conditionsmentioning

confidence: 99%

See 2 more Smart Citations

On the modeling of aiding mixed convection in vertical channels

Sun

Chénier

et al. 2012

Heat Mass Transfer

Self Cite

View full text Add to dashboard Cite

This paper aims at showing that to prescribe a flow rate at the inlet section of a vertical channel with heated walls leads to surprising and counterintuitive physical solutions, especially when the problem is modeled as elliptical. Such an approach can give rise to the onset of recirculation cells in the entry region while the heat transfer is slightly increased under the influence of the buoyancy force. We suggest an alternative model based on more realistic boundary conditions based on a prescribed total pressure at the inlet and a fixed pressure at the outlet sections. In this case, the pressure and buoyancy forces act effectively in the same direction and, the concept of buoyancy aiding convection makes sense. The numerical results emphasize the large differences between solutions based on prescribed inlet velocity and those obtained with the present pressure-based boundary conditions. List of symbols aThermal diffusivity (m 2 s -1 )c z Stretching parameters, Eq. 13 D Plate spacing (m) D h Hydraulic diameter, D h = 2D (m) g Gravitational acceleration (m s -2 ) Gr H Grashof number based on H, Gr H = gb 0 DTH 3 /m 0 2 h Heat transfer coefficient (W m -2 K -1 ) H Channel height (m) k Thermal conductivity (W m -1 K -1 ) L Channel length in the spanwise direction (m) _ m Mass flow rate (kg s -1 ) n x , n z Numbers of grid points in x-and z-directions p Pressure (Pa) p s Pressure at the outlet section (Pa) Pr Prandtl number, Pr = m 0 /a 0 Q Heat flux (W) Q en Enthalpy heat flux (W) Q 2w Convective heat flux along the two channel walls (W) Re Reynolds number based on D h , Re = w 0 D h /m 0 Ri Richardson number, Ri = Gr/Re 2 S c Area of the channel cross section, S c = DL (m 2 ) t Time (s) T Temperature (K) u, w Velocity components (m s -1 ) x, z Coordinates (m) Greeks b Coefficient of thermal expansion, b = 1/T 0 (K -1 ) DT Temperature difference, DT = (T h -T 0 ) (K) l Dynamic viscosity (Pa s) m Kinematic viscosity (m 2 s -1 ) q Density (kg m -3 ) h Dimensionless temperature ratio, h = (T -T 0 )/DT s Dimensionless time Subscripts a, b Analytical solutions h Hot wall H Quantity based on channel height nc Natural convection 0 Inlet section Superscripts -Averaged quantity * Dimensionless quantity

show abstract

Interaction between turbulence and thermal radiation in combined heat transfer channel flows

Moghaddam

Bazdidi–Tehrani

Aghaamini

2019

Heat Trans. Asian Res.

View full text Add to dashboard Cite

The aim of the present work is to examine the effects of interaction between turbulence and thermal radiation on the fully developed turbulent channel flow with variable properties in the presence of combined mixed convection‐radiation heat transfer. The vertical and horizontal channels under study are formed by differentially heated flat parallel plates. Large eddy simulation and the low Mach number approach are used to solve the governing equations. Also, the radiative transfer equation is solved using the P 1 method. The results are achieved by developing a solver in an open‐source computational fluid dynamics toolbox. The main focus is to find out whether neglecting turbulence‐radiation interaction (TRI) is a valid assumption for such flows under consideration. The present results show that, in both configurations, the maximum values of emission TRI and incident TRI are 2% and 3%, respectively. These results are consistent with the previous findings suggesting that in the nonreactive flows, these two terms are negligible.

show abstract

Flow reversal of laminar mixed convection in the entry region of symmetrically heated, vertical plate channels

Cited by 55 publications

References 27 publications

Numerical Analysis of the Parameters Governing 3D Laminar Mixed Convection Flow in a Rectangular Channel with Imposed Wall Flux Density

Numerical Analysis of the Parameters Governing 3D Laminar Mixed Convection Flow in a Rectangular Channel with Imposed Wall Flux Density

On the modeling of aiding mixed convection in vertical channels

Interaction between turbulence and thermal radiation in combined heat transfer channel flows

Contact Info

Product

Resources

About