Heat Transfer Enhancement of Impingement Cooling by Different Crossflow Diverters

2021 ◽  
Author(s):  
Juan He ◽  
Qinghua Deng ◽  
Kun Xiao ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Local Heat ◽  
Friction Loss ◽  
Navier Stokes ◽  
Impingement Cooling ◽  
Streamwise Location ◽  
Overall Evaluation ◽  
The Cost

Abstract Impingement cooling can effectively disperse local heat load, but its downstream heat transfer is always reduced due to crossflow effect. In this study, the flow and heat transfer characteristics of impingement cooling with Semi-Circular (SC), Semi-Rectangular (SR), Semi-Diamond (SD) and Semi-Four-pointed Star (SFS) crossflow diverters are compared over the ReD ranging from 3,500 to 14,000 by solving three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with SST k-? turbulence model. It is found that crossflow diverters change the distribution of local jet Reynolds number (ReD,j/ReD) and reduce the mass velocity ratio of downstream crossflow to jet (Gcf/Gj), so they enhance the heat transfer significantly, but also come at the cost of friction loss. Overall evaluation reveals that various crossflow diverters can improve the comprehensive heat transfer performance parameter (F), and the maximum increases are 11.0%, 14.3%, 12.2% and 14.7% for SC, SR, SD and SFS cases respectively. It is noted that the Nusselt number of heated SFS-shaped diverter surface is also the highest. Besides, the influences of streamwise location (L) and thickness (t) of SFS-shaped diverter are also investigated. Results show that the heat transfer and friction loss change a little when the L increases from 2D to 3D, but the heat transfer decreases sharply and friction loss increases seriously when the L increases from 3D to 4D. With respect to the t, it has almost no effect on the flow field and heat transfer.

The Effect of Turbulence on the Heat Transfer in Closed Gas-Filled Rotating Annuli

1998 ◽  
Vol 120 (4) ◽  
pp. 824-830 ◽  
Author(s):  
D. Bohn ◽  
J. Gier
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Navier Stokes ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Correction Scheme

Higher turbine inlet temperatures are a common measure for increasing the thermal efficiency of modern gas turbines. This development leads not only to the need for more efficient turbine blade cooling but also to the requirement for a more profound knowledge of the mechanically and thermally stressed parts of the rotor. For determining thermal stresses from the temperature distribution in the rotor of a gas turbine, one has to encounter the convective transfer in rotor cavities. In the special case of an entirely closed gas-filled rotating annulus, the convective flow is governed by a strong natural convection. Owen and other researchers have found that the presence of turbulence and its inclusion in the modeling of the flow causes significant differences in the flow development in rotating annuli with throughflow, e.g., different vortex structures. However, in closed rotating annuli there is still a lack of knowledge concerning the influence of turbulence. Based on previous work, in this paper the influence of turbulence on the flow structure and on the heat transfer is investigated. The flow is investigated numerically with a three-dimensional Navier–Stokes solver, based on a pressure correction scheme. To account for the turbulence, a low-Reynolds-number k–ε model is employed. The results are compared with experiments performed at the Institute of Steam and Gas Turbines. The computations demonstrate that turbulence has a considerable influence on the overall heat transfer as well as on the local heat transfer distribution. Three-dimensional effects are discussed by comparing the three-dimensional calculation with a two-dimensional calculation of the same configuration and are found to have some impact.

scholarly journals The Effect of Turbulence on the Heat Transfer in Closed Gas-Filled Rotating Annuli

1997 ◽  
Author(s):  
Dieter Bohn ◽  
Jochen Gier
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Navier Stokes ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Correction Scheme

Higher turbine inlet temperatures are a common measure for increasing the thermal efficiency of modern gas turbines. This development not only leads to the need for more efficient turbine blade cooling but also to the requirement of a more profound knowledge of the mechanically and thermally stressed parts of the rotor. For determining thermal stresses from the temperature distribution in the rotor of a gas turbine, one has to encounter the convective transfer in rotor cavities. In the special case of an entirely closed gas-filled rotating annulus the convective flow is governed by a strong natural convection. Owen and other researchers have found, that the presence of turbulence and its inclusion in the modeling of the flow causes significant differences in the flow development in rotating annuli with throughflow like e.g. different vortex structures. However, in closed rotating annuli there is still a lack of knowledge concerning the influence of turbulence. Based on previous work, in this paper the influence of turbulenceon the flow structure and on the heat transfer is investigated. The flow is investigated numerically with a three-dimensional Navier-Stokes solver, based on a pressure correction scheme. To account for the turbulence, a low-Reynolds-number k-ε-model is employed. The results are compared with experiments performed at the Institute of Steam and Gas Turbines. The computations demonstrate that turbulence has a considerable influence on the overall heat transfer as well as on the local heat transfer distribution. Three-dimensional effects are discussed by comparing the three-dimensional calculation with a two-dimensional calculation of the same configuration and are found to have some impact.

Jet Impingement Heat Transfer Enhancement With Different Crossflow Diverter Shapes

2021 ◽  
Author(s):  
Juan He ◽  
Qinghua Deng ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Performance ◽  
Velocity Ratio ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Friction Loss ◽  
Numerical Verification ◽  
Transfer Performance ◽  
Impingement Cooling

Abstract Impingement cooling is an effective cooling structure in gas turbine blades, but the downstream heat transfer will be reduced seriously by crossflow. It has been proven that equipping a crossflow diverter in impingement channel can make jet free from crossflow and enhance the downstream heat transfer. In this paper, in order to obtain a kind of crossflow diverter with advantageous heat transfer performance, the flow and heat transfer characteristics of four crossflow diverters (Semi-Circular (SC), Semi-Rectangular (SR), Semi-Diamond (SD) and Semi-Four-pointed Star (SFS)) are compared in detail. To this end, a Baseline impingement cooling configuration is considered, in which the pitches on the streamwise and spanwise directions of impingement jets are all 6D and the distance from jet to target surface is 2D. Through detailed numerical verification, SST k-ω turbulence model is finally selected, and all simulations are performed under Reynolds number ranging from 3,500 to 14,000. It is found that the crossflow diverter can change the local jet Reynolds number distribution and effectively reduce the local mass velocity ratio of crossflow to jet. Results reveal that the crossflow diverter increases the heat transfer and inevitably increases the friction loss, but all of them can improve the comprehensive heat transfer performance over the simulated flow range. When the Reynolds number is 14,000, the best heat transfer performance can be achieved, and the comprehensive heat transfer performance parameters of SC, SR, SD and SFS cases can increase by up to 11.0%, 14.3%, 12.2% and 14.7% respectively. After determining SFS-shaped crossflow diverter with the best comprehensive heat transfer performance, the influence of its streamwise position on heat transfer and friction loss is also studied. The SFS-shaped diverter is placed at 2D, 2.5D, 3D, 3.5D and 4D from the center of adjacent upstream jet, respectively. Results show that the heat transfer and friction loss change a little when the distance increases from 2D to 3D, but the heat transfer decreases sharply and friction loss increases seriously when the distance increases from 3D to 4D.

scholarly journals The Effect of Turbulence on the Heat Transfer in Closed Gas-Filled Rotating Annuli for Different Rayleigh Numbers

1998 ◽  
Author(s):  
Dieter Bohn ◽  
Jochen Gier
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Additional Term ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Navier Stokes ◽  
Rayleigh Numbers ◽  
Special Case

Higher turbine inlet temperatures are a common method of increasing the thermal efficiency of modern gas turbines. This development not only generates the need for more efficient turbine blade cooling but also demands a more profound knowledge of the mechanically and thermally stressed parts of the rotor. In order to determine thermal stresses from the temperature distribution in the rotor of a gas turbine, one has to encounter the convective heat transfer in rotor cavities. In the special case of a completely closed gas-filled rotating annulus the convective flow is governed by strong natural convection. As shown in a previous paper by the authors, and for example by Owen, the presence of turbulence and its inclusion in the modeling of the flow has been found to cause significant differences in the flow development in rotating annuli. This influence in the special case of a closed rotating annulus has been recently investigated by the authors for a moderately high Rayleigh-Number. Based on this work an investigation was undertaken focusing on the development of turbulence and turbulence related changes in the flow structure for increasing Rayleigh-Numbers. The flow is investigated numerically using a three-dimensional Navier-Stokes solver, based on a pressure correction scheme. To account for the turbulence, a low-Reynolds-number k-ε-model is employed. This model is complemented by an additional term for turbulence production due to buoyancy. The results are compared with experiments performed at the Institute of Steam and Gas Turbines. The computations demonstrate the considerable influence on the overall heat transfer as well as on the local heat transfer distribution.

scholarly journals A Code for Simulating Heat Transfer in Turbulent Channel Flow

Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 756
Author(s):  
Federico Lluesma-Rodríguez ◽  
Francisco Álcantara-Ávila ◽  
María Jezabel Pérez-Quiles ◽  
Sergio Hoyas
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulent Channel Flow ◽  
Passive Scalar ◽  
Direct Numerical Simulations ◽  
Time Dependent ◽  
Navier Stokes ◽  
Thermal Flow ◽  
Navier Stokes Equations

One numerical method was designed to solve the time-dependent, three-dimensional, incompressible Navier–Stokes equations in turbulent thermal channel flows. Its originality lies in the use of several well-known methods to discretize the problem and its parallel nature. Vorticy-Laplacian of velocity formulation has been used, so pressure has been removed from the system. Heat is modeled as a passive scalar. Any other quantity modeled as passive scalar can be very easily studied, including several of them at the same time. These methods have been successfully used for extensive direct numerical simulations of passive thermal flow for several boundary conditions.

Two Dimensional Simulations of Enhanced Heat Transfer in an Intermittently Grooved Channel

2000 ◽  
Author(s):  
M. Greiner ◽  
P. F. Fischer ◽  
H. M. Tufo
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Spectral Element ◽  
Local Heat ◽  
Navier Stokes ◽  
Computational Domain ◽  
Two Dimensional ◽  
Number Range ◽  
Element Technique ◽  
Outflow Boundary

Abstract Two-dimensional Navier-Stokes simulations of heat and momentum transport in an intermittently grooved passage are performed using the spectral element technique for the Reynolds number range 600 ≤ Re ≤ 1800. The computational domain has seven contiguous transverse grooves cut symmetrically into opposite walls, followed by a flat section with the same length. Periodic inflow/outflow boundary conditions are employed. The development and decay of unsteady flow is observed in the grooved and flat sections, respectively. The axial variation of the unsteady component of velocity is compared to the local heat transfer, shear stress and pressure gradient. The results suggest that intermittently grooved passages may offer even higher heat transfer for a given pumping power than the levels observed in fully grooved passages.

Three-Dimensional Natural Convection From Vertical Heated Plates With Adjoining Cool Surfaces

1992 ◽  
Vol 114 (1) ◽  
pp. 115-120 ◽  
Author(s):  
B. W. Webb ◽  
T. L. Bergman
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Control Volume ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Uniform Heat Flux ◽  
Infrared Thermal Imaging ◽  
Transfer Rates ◽  
Thermal Boundary Conditions

Natural convection in an enclosure with a uniform heat flux on two vertical surfaces and constant temperature at the adjoining walls has been investigated both experimentally and theoretically. The thermal boundary conditions and enclosure geometry render the buoyancy-induced flow and heat transfer inherently three dimensional. The experimental measurements include temperature distributions of the isoflux walls obtained using an infrared thermal imaging technique, while the three-dimensional equations governing conservation of mass, momentum, and energy were solved using a control volume-based finite difference scheme. Measurements and predictions are in good agreement and the model predictions reveal strongly three-dimensional flow in the enclosure, as well as high local heat transfer rates at the edges of the isoflux wall. Predicted average heat transfer rates were correlated over a range of the relevant dimensionless parameters.

Transpiration Cooling Using Porous Triple-Laminated Plates

2003 ◽  
Author(s):  
H. L. Wu ◽  
X. F. Peng
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Efficiency ◽  
Velocity Ratio ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Laminated Plates ◽  
Transpiration Cooling ◽  
Transfer Behavior ◽  
Crossflow Velocity

Transpiration cooling using porous triple-laminated plates was numerically investigated to understand the associated flow mechanism and heat transfer characteristics with/without crossflow. The flow structure and heat transfer behavior are very similar in the two laminate gaps, and crossflow has little influence on them. The cooling performance shows very good uniformity and high efficiency. Violent impingement and turbulent flow inside the plate contribute greatly to local heat transfer intensification. The cooling efficiency might be further improved with enhancement of film cooling effect, by enlarging the discharge holes to decrease the local jet-to-crossflow velocity ratio, or by using inclined discharge holes to increase the film attaching ability.

Turbine Airfoil Heat Transfer Predictions Using CFD

2005 ◽  
Author(s):  
Anil K. Tolpadi ◽  
James A. Tallman ◽  
Lamyaa El-Gabry
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Design System ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Airfoils ◽  
Typical Design

Conventional heat transfer design methods for turbine airfoils use 2-D boundary layer codes (BLC) combined with empiricism. While such methods may be applicable in the mid span of an airfoil, they would not be very accurate near the end-walls and airfoil tip where the flow is very three-dimensional (3-D) and complex. In order to obtain accurate heat transfer predictions along the entire span of a turbine airfoil, 3-D computational fluid dynamics (CFD) must be used. This paper describes the development of a CFD based design system to make heat transfer predictions. A 3-D, compressible, Reynolds-averaged Navier-Stokes CFD solver with k-ω turbulence modeling was used. A wall integration approach was used for boundary layer prediction. First, the numerical approach was validated against a series of fundamental airfoil cases with available data. The comparisons were very favorable. Subsequently, it was applied to a real engine airfoil at typical design conditions. A discussion of the features of the airfoil heat transfer distribution is included.

scholarly journals Heat Transfer on a Film-Cooled Rotating Blade

1999 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

A multi-block, three-dimensional Navier-Stokes code has been used to compute heat transfer coefficient on the blade, hub and shroud for a rotating high-pressure turbine blade with 172 film-cooling holes in eight rows. Film cooling effectiveness is also computed on the adiabatic blade. Wilcox’s k-ω model is used for modeling the turbulence. Of the eight rows of holes, three are staggered on the shower-head with compound-angled holes. With so many holes on the blade it was somewhat of a challenge to get a good quality grid on and around the blade and in the tip clearance region. The final multi-block grid consists of 4784 elementary blocks which were merged into 276 super blocks. The viscous grid has over 2.2 million cells. Each hole exit, in its true oval shape, has 80 cells within it so that coolant velocity, temperature, k and ω distributions can be specified at these hole exits. It is found that for the given parameters, heat transfer coefficient on the cooled, isothermal blade is highest in the leading edge region and in the tip region. Also, the effectiveness over the cooled, adiabatic blade is the lowest in these regions. Results for an uncooled blade are also shown, providing a direct comparison with those for the cooled blade. Also, the heat transfer coefficient is much higher on the shroud as compared to that on the hub for both the cooled and the uncooled cases.

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