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.

scholarly journals A detailed analysis of flow and heat transfer characteristics under a turbulent intermittent jet impingement on a concave surface

2021 ◽  
pp. 334-334
Author(s):  
Ali Hajimohammadi ◽  
Mehran Zargarabadi ◽  
Javad Mohammadpour
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Computational Study ◽  
Control Volume ◽  
Simple Algorithm ◽  
Jet Impingement ◽  
Concave Surface ◽  
Flow And Heat Transfer

A computational study is carried out of the three-dimensional flow field and heat transfer under a turbulent intermittent circular jet impingement on a concave surface. The control-volume procedure with the SIMPLE algorithm is employed to solve the unsteady RANS (use full form) equations. The RNG k-? model is implemented to simulate turbulence due to its success in predicting similar flows. The numerical results are validated by comparing them with the experimental data. The effects of jet Reynolds number and oscillation frequency on the flow and heat transfer are evaluated. The profiles of instantaneous and time-averaged Nusselt numbers exhibit different trends in axial (x) and circumferential (s) directions. It is found that increasing frequency from 50 to 200 Hz results in considerable time-averaged Nusselt number enhancement in both axial and curvature directions. The intermittent jet at a frequency of 200 Hz enhances the total average Nusselt number by 51.4%, 40%, and 33.7% compared to the steady jet values at jet Reynolds numbers of 10000, 23000, and 40000, respectively. In addition, a correlation for the average Nusselt number is proposed depending on the Reynolds number and the Strouhal number.

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

2010 ◽  
Author(s):  
Tarek M. Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.

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.

Two Dimensional Simulation of Flow and Heat Transfer Characteristics of Turbulent Jets

2010 ◽  
Author(s):  
Tarek Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Jets ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Dimensional Simulation

In this study, flow and heat transfer characteristics of two-dimensional impinging jets are investigated numerically. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume CFD code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results show that the Reynolds number has significant effect on the heat transfer rate and has no effect on the location of the maximum Nusselt number.

Wall distance effect on heat transfer at high flow velocity

2019 ◽  
Vol 91 (9) ◽  
pp. 1180-1186
Author(s):  
Marcin Kurowski ◽  
Ryszard Szwaba ◽  
Janusz Telega ◽  
Pawel Flaszynski ◽  
Fernando Tejero ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Flow Velocity ◽  
Impinging Jets ◽  
High Flow ◽  
Content Type ◽  
Wall Distance ◽  
Air Jets ◽  
Very High

Purpose This paper aims to present the results of experimental and numerical research on heat transfer distribution under the impinging jets at various distances from the wall and high jet velocity. This work is a part of the INNOLOT Program financed by National Centre for Research and Development. Design/methodology/approach The air jets flow out from the common pipe and impinge on a surface which is cooled by them, and in this way, all together create a model of external cooling system of low-pressure gas turbine casing. Measurements were carried out for the arrangement of 26 in-line jets with orifice diameter of 0.9 mm. Heat transfer distribution was investigated for various Reynolds and Mach numbers. The cooled wall, made of transparent PMMA, was covered with a heater foil on which a layer of self-adhesive liquid crystal foil was placed. The jet-to-wall distance was set to h = from 4.5 to 6 d. Findings The influence of various Reynolds and Mach numbers on cooled flat plate and jet-to-wall distance in terms of heat transfer effectiveness is presented. Experimental results used for the computational fluid dynamics (CFD) model development, validation and comparison with numerical results are presented. Practical implications Impinging air jets is a commonly used technique to cool advanced turbines elements, as it produces large convection enhancing the local heat transfer, which is a critical issue in the development of aircraft engines. Originality/value The achieved results present experimental investigations carried out to study the heat transfer distribution between the orthogonally impinging jets from long round pipe and flat plate. Reynolds number based on the jet orifice exit conditions was varied between 2,500 and 4,000; meanwhile, for such Re, the flow velocity in jets was particularly very high, changing from M = 0.56 to M = 0.77. Such flow conditions combination, i.e. the low Reynolds number and very high flow velocity cannot be found in the existing literature.

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.

scholarly journals Fluid Flow and Heat Transfer in an Internal Coolant Passage

2001 ◽  
Vol 7 (5) ◽  
pp. 351-364 ◽  
Author(s):  
Tom I.-P. Shih ◽  
Yu-Liang Lin ◽  
Mark A. Stephens
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
High Reynolds Number ◽  
Computational Study ◽  
Reynolds Shear Stress ◽  
Secondary Flows ◽  
Flow And Heat Transfer ◽  
Rotation Numbers ◽  
Low Reynolds ◽  
High Reynolds

Computations were performed to study the three-dimensional flow and heat transfer in a U-shaped duct of square cross section with inclined ribs on two opposite walls under rotating and non-rotating conditions. Two extreme limits in the Reynolds number (25,000 and 350,000) were investigated. The rotation numbers investigated are 0, 0.24, and 0.039. Results show rotation and the bend to reinforce secondary flows that align with it and to retard those that do not. Rotation was found to affect significantly the flow and heat transfer in the bend even at a very high Reynolds number of 350,000 and a very low Rotation number of 0:039. When there is no rotation, the flow and heat transfer in the bend were dominated by rib-induced secondary flows at the high Reynolds number limit and by bend-induced pressure-gradients at the low Reynolds number limit. Long streaks of reduced surface heat transfer occur in the bend at locations where streamlines from two contiguous secondary flows merge and then flow away from the surface. The location and size of these streaks varied markedly with Reynolds and rotation numbers.This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Turbulence is modelled by the low-Reynolds shear-stress transport (SST) model of Menter. Solutions were generated by using a cell-centered, finite-volume method, that is based on second-order accurate flux-difference splitting and a diagonalized alternating-direction implicit scheme with local time-stepping and V-cycle multigrid.

Flow and Heat Transfer in a Jet-Impingement Configuration With No Cross Flows About Impinging Jets

2012 ◽  
Author(s):  
C.-S. Lee ◽  
T. I-P. Shih ◽  
K. M. Bryden ◽  
R. Ames ◽  
R. A. Dennis
Keyword(s):  
Heat Transfer ◽  
Transport Model ◽  
Computational Study ◽  
Cross Flow ◽  
Jet Impingement ◽  
Target Surface ◽  
Impinging Jets ◽  
Mean Velocity ◽  
Wall Functions ◽  
Flow And Heat Transfer

Computations were performed to study the flow and heat transfer in a jet-impingement configuration in which there is no cross flow about the impinging cooling jets. The configuration consists of two sets of staggered arrays of holes with one array of holes for jets to impinge and cool a target wall with or without strategically positioned pin fins and a second array positioned midway relative to the first array of holes for the impinging jets to exit the configuration. For this configuration, the following parameter were investigated: distance between the jet-hole exit and the target surface to be cooled (H/d = 0.5, 1, 4), spacing between jets (S/d = 2, 4), and pin-fin height (Hp/d = 0, 1, 2) on the target surface, where d is the diameter of the holes in the arrays. Also, the jet-impingement velocity was varied to study a range Reynolds numbers based on the hole diameter d and the mean velocity of the jet in the hole (Red = 20,000, 40,000, and 60,000). For all cases studied, the temperature of the coolant air is 673 K; the wall to be cooled is maintained at 1,273 K; and the static pressure at the exit of the jet-impingement array is maintained at 25 bars. This computational study is based on steady RANS – compressible Navier-Stokes with the shear-stress transport model for turbulence where integration is to the wall (i.e., wall functions were not used) and temperature-dependent properties are accounted for.

scholarly journals Flow and Heat Transfer in a Ribbed U-Duct Under Typical Engine Conditions

1998 ◽  
Author(s):  
T. I-P. Shih ◽  
Y.-L. Lin ◽  
M. A. Stephens ◽  
M. K. Chyu ◽  
K. C. Civinskas
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Gas Turbines ◽  
Computational Study ◽  
Three Dimensional ◽  
Eddy Diffusivity ◽  
Reynolds Stress Model ◽  
Operating Conditions ◽  
Coolant Flow ◽  
Flow And Heat Transfer

Computations were performed to study the three-dimensional flow and heat transfer in a ribbed U-shaped duct of square cross section under operating conditions that are typical of industrial gas turbines. Basically, all walls were maintained at a temperature of 800 K, and the coolant air at the duct inlet had a temperature of 550 K and a pressure of 10 atm. Both rotating and non-rotating cases were investigated. When rotating, the angular speed was 3,600 rpm. The Reynolds number based on the duct hydraulic diameter was set at 350,000, which represents an upper limit in coolant flow. The results obtained in this study were compared with those from previous numerical studies with a lower Reynolds number, namely 25,000, which represents a lower limit in coolant flow. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Turbulence is modelled by two low-Reynolds number k-ω models: an SST version with isotropic eddy diffusivity and a nonlinear version with anisotropic eddy diffusivity from an explicit algebraic Reynolds stress model. Solutions were generated by using a cell-centered finite-volume method, that is based on flux-difference splitting and a diagonalized alternating-direction implicit scheme with local time-stepping and V-cycle multigrid.

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