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.

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.

A Presentation of Detailed Experimental Data of a Suction Side Film Cooled Turbine Cascade

2000 ◽  
Author(s):  
Holger Brandt ◽  
Wolfgang Ganzert ◽  
Leonhard Fottner
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Gas Turbines ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Suction Side ◽  
Local Heat ◽  
Turbine Cascade ◽  
Shaped Hole

This paper presents detailed isothermal investigations on the aerodynamic effects and the heat transfer of suction side film cooling on a highly loaded turbine cascade. The measurements were carried out with inlet flow conditions kept constant at values which are typically found in modern gas turbines. Five configurations with different hole geometries were investigated, a cylindrical hole with two different streamwise inclination angles, a fan shaped hole and a fan shaped hole with laid-back both only inclined in streamwise direction and a fan shaped hole with laid-back and combined streamwise and lateral inclination. The variation of the blowing ratio enabled closer studies of the mixing process and the influence of the various hole configurations on the aerodynamics and the local heat transfer. To enhance the understanding of the mechanisms and the boundary layer behaviour of these highly three-dimensional flows, much effort has been put on the measurement techniques. The high-resolution data needed was obtained using pressure tappings positioned on the profile, oil-and-dye visualizations on the suction surface, pneumatic probes in the wake and three-dimensional hot wire anemometry in the flow field downstream the holes. Additional heat transfer examinations with a special set-up based on the steady state liquid crystal technique clarified the individual local heat transfer distributions. All measured data are summarized and documented to be used as a reference for three-dimensional, steady-state numerical calculations.

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

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.

Development of High Order LES Solver for Heat Transfer Applications Based on the Open Source OpenFOAM Framework

2015 ◽  
Author(s):  
Luca Mangani ◽  
David Roos Launchbury ◽  
Ernesto Casartelli ◽  
Giulio Romanelli
Keyword(s):  
Heat Transfer ◽  
Open Source ◽  
Gas Turbines ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
High Order ◽  
Computational Time

The computation of heat transfer phenomena in gas turbines plays a key role in the continuous quest to increase performance and life of both component and machine. In order to assess different cooling approaches computational fluid dynamics (CFD) is a fundamental tool. Until now the task has often been carried out with RANS simulations, mainly due to the relatively short computational time. The clear drawback of this approach is in terms of accuracy, especially in those situations where averaged turbulence-structures are not able to capture the flow physics, thus under or overestimating the local heat transfer. The present work shows the development of a new explicit high-order incompressible solver for time-dependent flows based on the open source C++ Toolbox OpenFOAM framework. As such, the solver is enabled to compute the spatially filtered Navier-Stokes equations applied in large eddy simulations for incompressible flows. An overview of the development methods is provided, presenting numerical and algorithmic details. The solver is verified using the method of manufactured solutions, and a series of numerical experiments is performed to show third-order accuracy in time and low temporal error levels. Typical cooling devices in turbomachinery applications are then investigated, such as the flow over a turbulator geometry involving heated walls and a film cooling application. The performance of various sub-grid-scale models are tested, such as static Smagorinsky, dynamic Lagrangian, dynamic one-equation turbulence models, dynamic Smagorinsky, WALE and sigma-model. Good results were obtained in all cases with variations among the individual models.

scholarly journals Numerical heat transfer analysis of micro-scale jet-impingement cooling in a high-pressure turbine vane

2021 ◽  
Author(s):  
Karan Anand
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Analysis ◽  
Transfer Rates ◽  
Numerical Heat Transfer ◽  
Turbine Vane ◽  
Single Jet

This research provides a computational analysis of heat transfer due to micro jet-impingement inside a gas turbine vane. A preliminary-parametric analysis of axisymmetric single jet was reported to better understand micro jet-impingement. In general, it was seen that as the Reynolds number increased the Nusselt number values increased. The jet to target spacing had a considerably lower impact on the heat transfer rates. Around 30% improvement was seen by reducing the diameter to half while changing the shape to an ellipse saw 20.8% improvement in Nusselt value. The numerical investigation was then followed by studying the heat transfer characteristics in a three-dimensional, actual-shaped turbine vane. Effects of jet inclination showed enhanced mixing and secondary heat transfer peaks. The effect of reducing the diameter of the jets to 0.125 mm yielded 55% heat transfer improvements compared to 0.51 mm; the tapering effect also enhanced the local heat transfer values as local velocities at jet exit increased.

Local Heat Transfer Characteristics in Simulated Electronic Modules

2003 ◽  
Vol 125 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Seong-Yeon Yoo ◽  
Jong-Hark Park ◽  
Min-Ho Chung
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Dimensional Array ◽  
Transfer Characteristics

When heat is released by forced convection from electronic modules in a narrow printed circuit board channel, complex flow phenomena—such as stagnation and acceleration on the front surface, separation and reattachment on the top surface, wake or cavity flow near the rear surface—affect the heat transfer characteristics. The purpose of this study is to investigate how these flow conditions influence the local heat transfer from electronic modules. Experiments are performed on a three-dimensional array of hexahedral elements as well as on a two-dimensional array of rectangular elements. Naphthalene sublimation technique is employed to measure three-dimensional local mass transfer, and the mass transfer data are converted to their counterparts of the heat transfer process using the analogy equation between heat and mass transfer. Module location and streamwise module spacing are varied, and the effect of vortex generators on heat transfer enhancement is also examined. Dramatic change of local heat transfer coefficients is found on each surface of the module, and three-dimensional modules have a little higher heat transfer value than two-dimensional modules because of bypass flow. Longitudinal vortices formed by vortex generator enhance the mixing of fluids and thereby heat transfer, and the rectangular wing type vortex generator is found to be more effective than the delta wing type vortex generator.

Three-Dimensional Transient Heat Conduction Equation Solution for Accurate Quantification of Heat Transfer Coefficient in Transient Liquid Crystal Experiments

2019 ◽  
Author(s):  
Shoaib Ahmed ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Conduction Model

Abstract Liquid crystal thermography and infrared thermography techniques are typically employed to measure detailed surface temperatures, where local heat transfer coefficient (HTC) values are calculated by employing suitable conduction models. One such practice, which is very popular and easy to use, is the transient liquid crystal thermography using one-dimensional semi-infinite conduction model. In these experiments, a test surface with low thermal conductivity and low thermal diffusivity (e.g. acrylic) is used where a step-change in coolant air temperature is induced and surface temperature response is recorded. An error minimization routine is then employed to guess heat transfer coefficients of each pixel, where wall temperature evolution is known through an analytical expression. The assumption that heat flow in the solid is essentially in one-dimension, often leads to errors in HTC determination and this error depends on true HTC, wall temperature evolution and HTC gradient. A representative case of array jet impingement under maximum crossflow condition has been considered here. This heat transfer enhancement concept is widely used in gas turbine leading edge and electronics cooling. Jet impingement is a popular cooling technique which results in high convective heat rates and has steep gradients in heat transfer coefficient distribution. In this paper, we have presented a procedure for solution of three-dimensional transient conduction equation using alternating direction implicit method and an error minimization routine to find accurate heat transfer coefficients at relatively lower computational cost. The HTC results obtained using 1D semi-infinite conduction model and 3D conduction model were compared and it was found that the heat transfer coefficient obtained using the 3D model was consistently higher than the conventional 1D model by 3–16%. Significant deviations, as high as 8–20% in local heat transfer at the stagnation points of the jets were observed between h1D and h3D.

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