Computational simulations of buoyancy-influenced turbulent flow and heat transfer in a vertical plane passage

2004 ◽  
Vol 218 (11) ◽  
pp. 1385-1397 ◽  
Author(s):  
J Wang ◽  
J Li ◽  
S He ◽  
J D Jackson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Computational Study ◽  
Convective Heat Transfer Coefficient ◽  
Vertical Plane ◽  
Heated Wall ◽  
Computational Simulations ◽  
Variable Property ◽  
Flow And Heat Transfer

Computational simulations are reported of some recent experiments on turbulent variable-property mixed convection to air flowing upwards and downwards through a vertical plane passage, one wall of which was uniformly heated. In addition to heat transfer from that wall by convection, there was some radiative heat transfer to the opposite wall. In the experimental study, measurements were made of profiles of velocity and turbulence within the flow, and also local values of convective heat transfer coefficient were determined along the heated wall. The Reynolds number was varied from 44000 down to 7000 and the Grashof number from 3.0 × 108 to 9.0 × 09. To simulate the experiments by computational means, the governing equations for variable-property buoyancy-influenced two-dimensional turbulent flow and heat transfer in Reynolds-averaged form were solved using an elliptic formulation in conjunction with two well-known low-Reynolds-number k-e turbulence models. In this paper, results from the computational study are compared directly with experiment. In general, the observed effects of buoyancy on flow and heat transfer were satisfactorily reproduced but there were some clear discrepancies between the predictions and the experimental results, especially with downward flow under conditions where the influence of buoyancy was strong.

Prediction of Turbulent Flow and Heat Transfer in a Ribbed Rectangular Duct With and Without Rotation

1993 ◽  
Author(s):  
C. Prakash ◽  
R. Zerkle
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Case ◽  
Rectangular Duct ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Smooth Channel

The present study deals with the numerical prediction of turbulent flow and heat transfer in a 2:1 aspect ratio rectangular duct with ribs on the two shorter sides. The ribs are of square cross–section, staggered and aligned normal (90–deg) to the main flow direction. The ratio of rib height to duct hydraulic diameter equals 0.063, and the ratio of rib spacing to rib height equals 10. The duct may be stationary or rotating. The axis of rotation is normal to the axis of the duct and parallel to the ribbed walls (i.e., the ribbed walls form the leading and the trailing faces). The problem is three–dimensional and fully elliptic; hence, for computational economy, the present analysis deals only with a periodically–fully–developed situation where the calculation domain is limited to the region between two adjacent ribs. Turbulence is modelled with the k–epsilon model in conjunction with wall–functions. However, since the rib height is small, use of wall–functions necessitates that the Reynolds number be kept high. (Attempts to use a two–layer model that permits integration to the wall did not yield satisfactory results and such modelling issues are discussed at length). Computations are made here for Reynolds number in the range (30,000–100,000) and for Rotation number=0 (stationary), 0.06, and 0.12. For the stationary case, the predicted heat transfer agrees well with the experimental correlations. Due to the Coriolis induced secondary flow, rotation is found to enhance heat transfer from the trailing and the side walls, while decreasing heat transfer from the leading face. Relative to the corresponding stationary case, the effect of rotation is found to be less for a ribbed channel as compared to a smooth channel.

scholarly journals Effect of the attack angle of the ribs on the flow and heat transfer in a flat channel

2021 ◽  
Vol 2119 (1) ◽  
pp. 012027
Author(s):  
A V Barsukov ◽  
V V Terekhov ◽  
V I Terekhov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Inclination Angle ◽  
Attack Angle ◽  
Flat Channel ◽  
Optimal Angle ◽  
Average Heat ◽  
Flow And Heat Transfer

Abstract The results of numerical simulation of a turbulent flow in a flat channel with periodic inclined ribs by the RANS method are presented. The Reynolds number, calculated from the rib height and the superficial velocity, is Re = 12600. The obtained data are analyzed in order to determine the influence of the inclination angle on heat transfer. It is shown that the optimal angle of inclination, at which the average heat transfer in the channel is maximum, is 60°.

Laminar Fluid Flow and Heat Transfer in a Lid-Driven Cavity Due to a Thin Fin

2002 ◽  
Vol 124 (6) ◽  
pp. 1056-1063 ◽  
Author(s):  
Xundan Shi ◽  
J. M. Khodadadi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Computational Study ◽  
Reynolds Numbers ◽  
Left Wall ◽  
Driven Cavity ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity ◽  
The Right ◽  
Steady Laminar

A finite-volume-based computational study of steady laminar flow and heat transfer (neglecting natural convection) within a lid-driven square cavity due to a single thin fin is presented. The lid moves from left to right and a fixed thin fin can be positioned perpendicular to any of the three stationary walls. Three fins with lengths equal to 5, 10, and 15 percent of the side, positioned at 15 locations were examined for Re=500, 1000, 2000, and Pr=1 (total of 135 cases). Placing a fin on the right wall brings about multi-cell recirculating vortices compared to the case without a fin that exhibits a primary vortex and two small corner cells. A fin slows the flow near the anchoring wall and reduces the temperature gradients, thus degrading heat transfer capacity. A fin positioned near the top right corner of the cavity can reduce heat transfer most effectively in cases with all three different Reynolds numbers and lengths. Regardless of the Reynolds number, placing a fin on the right wall—compared to putting a fin on the left and bottom walls—can always enhance heat transfer on the left wall and at the same time, reduce heat transfer on the bottom, right and top walls. A long fin has the most marked effect on the system’s heat transfer capabilities. Mean Nusselt number was successfully correlated to the Reynolds number, length of the fin and its position.

Computational Investigations of Flow and Heat Transfer on an Effused Concave Surface With a Single Row of Impinging Jets for Different Exit Configurations

2009 ◽  
Author(s):  
M. Ashok Kumar ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Computational Study ◽  
Impinging Jets ◽  
Concave Surface ◽  
Local Enhancement ◽  
Stagnation Line ◽  
Single Row ◽  
Air Jets ◽  
Flow And Heat Transfer

A computational study is reported on flow and heat transfer from single row of circular air jets impinging on a concave surface with either one or two rows of effusion holes and without effusion holes. The effects of arrangement of jet orifices and effusion holes, spent air exit closure configurations, H/D ratio and jet Reynolds number are investigated. The pressure distribution is higher for the configuration with the air exit only through effusion holes. At higher Reynolds number, three peaks in local Nusselt number are identified and explained. Among the cases tested, the configuration with single row of inline effusion holes shows the least heat transfer and there is a significant local enhancement in heat transfer along the stagnation line for single row of staggered effusion holes. However, the effect of arrangement is negligible for two rows of effusion holes. Among the configuration tested the case of one edge open exit configuration with single row of staggered effusion holes (Case-C1s) shows higher heat transfer among others.

Direct numerical simulation of turbulent flow and heat transfer in a spatially developing turbulent boundary layer laden with particles

2018 ◽  
Vol 845 ◽  
pp. 417-461 ◽  
Author(s):  
Dong Li ◽  
Kun Luo ◽  
Jianren Fan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Solid Particles ◽  
Heated Wall ◽  
Wall Region ◽  
Flow And Heat Transfer ◽  
Particle Laden Flows ◽  
Near Wall

Direct numerical simulations of particle-laden flows in a spatially developing turbulent thermal boundary layer over an isothermally heated wall have been performed with realistic fully developed turbulent inflow boundary conditions. To the authors’ best knowledge, this is the first time the effects of inertial solid particles on turbulent flow and heat transfer in a flat-plate turbulent boundary layer have been investigated, using a two-way coupled Eulerian–Lagrangian method. Results indicate that the presence of particles increases the mean streamwise velocity and temperature gradients of the fluid in the near-wall region. As a result, the skin-friction drag and heat transfer are significantly enhanced in the particle-laden flows with respect to the single-phase flow. The near-wall sweep and ejection motions are suppressed by the particles and hence the Reynolds shear stress and wall-normal turbulent heat flux are attenuated, which leads to reductions in the production of the turbulent kinetic energy and temperature fluctuations. In addition, the coherence and spacing of the near-wall velocity and temperature streaky structures are distinctly increased, while the turbulent vortical structures appear to be disorganized under the effect of the particles. Moreover, the intensity of the streamwise vortices decreases monotonically with increasing particle inertia.

Investigation of the characteristics of turbulent flow and heat transfer induced by a vibrating piezoelectric fan on asymmetrical concave surfaces

2021 ◽  
pp. 095765092110260
Author(s):  
Xinjun Li ◽  
Weiwei Chen ◽  
Shihua Lu
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Convective Heat Transfer Coefficient ◽  
Displacement Function ◽  
Concave Surface ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Offset Distance ◽  
Mesh Technique

This paper aims at performing an investigation numerically on the turbulent flow and thermal performances for an asymmetrical concave surface integrated with a slim vibrating piezoelectric fan. The dynamic mesh technique using a user defined function to describe the displacement function of vibrating cantilever beam is employed to model the deformation of the slim piezoelectric fan in time. Meanwhile, the SST k-ω turbulence model is chosen to capture the turbulence behavior of the flow and heat transfer. Two important factors, the relative curvature of the both sides of semicircular surfaces ( RK) and the dimensionless distance of fan offset along y-axis (Δ y/ APP) are taken into considerations during the simulation process. A considerable increase of local time-average heat transfer coefficients is observed in the vicinity of vibration envelope. The results show that the relative curvature ( RK) has a strong influence on the flow and heat transfer at both ends of the asymmetrical concave surface when its value is larger than 2. And by adjusting the dimensionless offset distance of the piezoelectric fan (Δ y/ APP), the area-averaged convective heat transfer coefficient can be increased by 20% on a small zone surrounding the fan with WPF ×  App (S1). The conclusions of this paper implement a theoretical attempt for expanding the application scenarios of piezoelectric fan.

Numerical Prediction of Turbulent Flow and Heat Transfer Enhancement in a Square Passage With Various Truncated Ribs on One Wall

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Gongnan Xie ◽  
Jian Liu ◽  
Weihong Zhang ◽  
Giulio Lorenzini ◽  
Cesare Biserni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Numerical Study ◽  
Skew Angle ◽  
Transfer Enhancement ◽  
Reduced Pressure ◽  
Flow And Heat Transfer

Repeated ribs are often employed in the midsection of internal cooling passages of turbine blades to augment the heat transfer by air flowing through the internal ribbed passages. Though the research of flow structure and augmented heat transfer inside various ribbed passages has been well conducted, previous works mostly paid much attention to the influence of rib topology (height-to-pitch, blockage ratio, skew angle, rib shape). The possible problem involved in the usage of ribs (especially with larger blockage ratios) is pressure loss penalty. Thus, in this case, the design of truncated ribs whose length is less than the passage width might fit the specific cooling requirements when pressure loss is critically considered. A numerical study of truncated ribs on turbulent flow and heat transfer inside a passage of a gas turbine blade is performed when the inlet Reynolds number ranges from 8000 to 24,000. Different truncation ratio (truncated-length to passage-width) rib geometries are designed and then the effect of truncation ratio on the pressure drop and heat transfer enhancement is observed under the condition of constant total length. The overall performance characteristics of various truncated rib passages are also compared. It is found that the heated face with a rib that is truncated 12% in length in the center (case A) has the highest heat transfer coefficient, while the heated face with a rib that is truncated 4% at three locations over its length, in the center and two sides (case D), has a reduced pressure loss compared with passages of other designs and provides the lowest friction factors. Although case A shows larger heat transfer augmentation, case D can be promisingly used to augment side-wall heat transfer when the pressure loss is considered and the Reynolds number is relatively large.

Sign in / Sign up

Export Citation Format

Share Document