Effect of Turning Vane Configurations on Heat Transfer and Pressure Drop in a Ribbed Internal Cooling System

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Wei Chen ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulence Model ◽  
Cooling System ◽  
Turbulence Models ◽  
Loss Coefficient ◽  
Test Cases ◽  
Convective Cooling ◽  
Blade Cooling ◽  
Turn Region

The ribbed serpentine blade cooling system is a typical configuration in the modern gas turbine airfoil. In this study, experimental and the numerical efforts were carried out to investigate the local heat transfer and pressure drop distribution of a ribbed blade cooling system with different configurations in the turn region. A test rig containing a ribbed rectangular U-duct with a 180 deg round turn was built in Tsinghua University for this study. The transient liquid crystal method was applied to get the heat transfer distribution. Nine test cases with three turn configurations under three Reynolds numbers were carried out in the experiment. Pressure was measured along the duct in order to determine the influence of turning vane configurations on pressure drop. The test cases were also analyzed numerically based on Reynolds-averaged Navier-Stokes (RANS) with three different turbulence models: the k-ε model, the SST reattachment model, and the Omega Reynolds stress (ORS) turbulence model. Both the experimental and numerical results showed a significant influence of the turning vane configuration on the heat transfer and pressure drop in the convective cooling channel. Among the three configurations, the loss coefficient of turn in configuration 2 was lowest due to the introduction of turning vane. Even the ribs were added in the turn region of configuration 3, the loss coefficient and friction factor are reduced by 23% and 17.5%, respectively. Meanwhile, the heat transfer in baseline configuration is still the highest. As the introduction of turning vane, the heat transfer in the region after turn was reduced by 35%. In configuration 3, the heat transfer in the turn region was enhanced by 15% as the ribs installed in the turn region. In the before turn region, the pressure drop and heat transfer was not influenced by the turn configuration. All the turbulence models captured the trend of heat transfer and pressure drop distribution of three test sections correctly, but all provide overpredicted heat transfer results. Among the models, the ORS turbulence model provided the best prediction. While aiming at high heat transfer level and low pressure drop, it is suggested that a suitable turn configuration, especially with the turning vane and/or the ribs, is a promising way to meet the conflicted requirements of the heat transfer and pressure drop in the convective cooling system.

Effect of Turning Vane Configurations on Heat Transfer and Pressure Drop in a Ribbed Internal Cooling System

2010 ◽  
Author(s):  
Wei Chen ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulence Model ◽  
Cooling System ◽  
Turbulence Models ◽  
Loss Coefficient ◽  
Test Cases ◽  
Convective Cooling ◽  
Blade Cooling ◽  
Turn Region

The ribbed serpentine blade cooling system is a typical configuration in the modern gas turbine airfoil. In this study, the experimental and the numerical efforts were carried out to investigate the local heat transfer and pressure drop distribution of a ribbed blade cooling system with different configurations in the turn region. A test rig containing a ribbed rectangular U-duct with a 180° round turn was built in Tsinghua University for this study. Transient liquid crystal method was applied to get the heat transfer distribution. Nine test cases with three turn configurations under three Reynolds numbers were carried out in the experiment. Pressure was measured along the duct in order to determine the influence of turning vane configurations on pressure drop. The test cases were also analyzed numerically based on RANS with three different turbulence models: the k-ε model, the SST reattachment model, and the Omega Reynolds Stress turbulence model. Both the experimental and the numerical results showed a significant influence of the turning vane configuration on the heat transfer and pressure drop in the convective cooling channel. Among the three configurations, the loss coefficient of turn in configuration 2 was lowest, due to the introduction of turning vane. Even the ribs were added in turn region of configuration 3, the loss coefficient and friction factor are reduced by 23% and 17.5%, respectively. Meanwhile, the heat transfer in baseline configuration is still the highest. As the introduction of turning vane, the heat transfer in the region after turn was reduced by 35%. In configuration 3, the heat transfer in the turn region was enhanced by 15% as the ribs installed in the turn region. In the before turn region, the pressure drop and heat transfer was not influenced by the turn configuration. All the turbulence models captured the trend of heat transfer and pressure drop distribution of three test sections correctly, but all provide overpredicted heat transfer results. Among the models, the ORS turbulence model provided the best prediction. While aiming at high heat transfer level and low pressure drop, it is suggested that, a suitable turn configuration, especially with the turning vane and/or the ribs, is a promising way to meet the conflicted requirements of the heat transfer and pressure drop in the convective cooling system.

Verification of RANS for Analyzing Convective Cooling System With and Without Ribs

2009 ◽  
Author(s):  
Wei Chen ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Turbulence Model ◽  
Cooling System ◽  
Reynolds Numbers ◽  
Convective Cooling ◽  
Turn Region ◽  
Good Agreement ◽  
Rans Method

Accurate prediction of pressure drop and heat transfer in convective cooling system is of importance to gas turbine industry. In the present paper, a detailed study and assessment of RANS method based on SST reattach turbulence model is performed on a convective cooling system in three kinds of U-duct: smooth, with 45 degree or 90 degree angled parallel ribs. Heat transfer and pressure drop distributions in the ducts are analyzed spatially at the Reynolds numbers of 15000, 30000 and 60000. The numerical results are compared with the experimental data and the empirical correlation from Han et al. It is found that the obtained pressure drop distribution based on RANS with SST reattach turbulence model matches the experimental data for all the U-ducts adequately. Meanwhile, the heat transfer is well predicted by the RANS method in the cases of smooth duct and 45 degree ribbed duct. A good agreement is obtained in the turn region of 45 degree ribbed duct, it owes to the strong secondary flow induced by ribs, which restrain the mainstream to separate and accelerate in the turn. But, the heat transfer is significantly under-predicted for 90 degree ribbed duct since the flow reattachment point between the ribs is predicted farther away from the upstream rib than that in the experiment. Therefore, it is suggested that the RANS method with a suitable turbulence model is valuable for the smooth and 45 degree ribbed U-duct with the acceptable engineering accuracy. But the prediction of heat transfer in 90 degree ribbed U-duct is still a challenge for the RANS to solve.

Application of the v2-f Turbulence Model to Turbomachinery Configurations

2007 ◽  
Author(s):  
B. Tartinville ◽  
E. Lorrain ◽  
Ch. Hirsch
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Critical Issue ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Test Cases ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Flow Features

Enhancing the representation of turbulence processes is a critical issue for CFD codes devoted to turbomachinery industry. Though more complex methods are available, Reynolds-Averaged Navier-Stokes models are widely used in the daily design process. Therefore, there is a constant need for improving eddy-viscosity based turbulence models. The present work aims at investigating the capabilities of the v2-f turbulence model for turbomachinery applications. Three types of flow features that are of importance for such applications are investigated in details: heat transfer, secondary flows, and laminar to turbulent transition. From a series of test cases, it appears that the v2-f turbulence model is specially adapted for heat transfer applications and shows potentialities in predicting laminar to turbulent transition.

Extended Models for Transitional Rough Wall Boundary Layers With Heat Transfer: Part I—Model Formulations

2008 ◽  
Author(s):  
M. Stripf ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boundary Layers ◽  
Turbulence Model ◽  
Turbulence Intensity ◽  
Discrete Element ◽  
Rough Wall ◽  
Test Cases ◽  
Wall Boundary ◽  
Turbine Vane

Two extended models for the calculation of rough wall transitional boundary layers with heat transfer are presented. Both models comprise a new transition onset correlation, which accounts for the effects of roughness height and density, turbulence intensity and wall curvature. In the transition region, an intermittency equation suitable for rough wall boundary layers is used to blend between the laminar and fully turbulent state. Finally, two different submodels for the fully turbulent boundary layer complete the two models. In the first model, termed KS-TLK-T in this paper, a sand roughness approach from Durbin et al., which builds upon a two-layer k-ε-turbulence model, is used for this purpose. The second model, the so-called DEM-TLV-T model, makes use of the discrete-element roughness approach, which was recently combined with a two-layer k-ε-turbulence model by the present authors. The discrete element model will be formulated in a new way suitable for randomly rough topographies. Part I of the paper will provide detailed model formulations as well as a description of the database used for developing the new transition onset correlation. Part II contains a comprehensive validation of the two models, using a variety of test cases with transitional and fully turbulent boundary layers. The validation focuses on heat transfer calculations on both, the suction and the pressure side of modern turbine airfoils. Test cases include extensive experimental investigations on a high-pressure turbine vane with varying surface roughness and turbulence intensity, recently published by the current authors as well as new experimental data from a low-pressure turbine vane. In the majority of cases, the predictions from both models are in good agreement with the experimental data.

Computational Fluid Dynamics Evaluation of Heat Transfer Correlations for Sodium Flows in a Heat Exchanger

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Seok-Ki Choi ◽  
Seong-O Kim ◽  
Hoon-Ki Choi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulence Model ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Cross Flow ◽  
Turbulence Models ◽  
Parallel Flow ◽  
Sst Model ◽  
Heat Transfer Correlations

A numerical study for the evaluation of heat transfer correlations for sodium flows in a heat exchanger of a fast breeder nuclear reactor is performed. Three different types of flows such as parallel flow, cross flow, and two inclined flows are considered. Calculations are performed for these three typical flows in a heat exchanger changing turbulence models. The tested turbulence models are the shear stress transport (SST) model and the SSG-Reynolds stress turbulence model by Speziale, Sarkar, and Gaski (1991, “Modelling the Pressure-Strain Correlation of Turbulence: An Invariant Dynamical System Approach,” J. Fluid Mech., 227, pp. 245–272). The computational model for parallel flow is a flow past tubes inside a circular cylinder and those for the cross flow and inclined flows are flows past the perpendicular and inclined tube banks enclosed by a rectangular duct. The computational results show that the SST model produces the most reliable results that can distinguish the best heat transfer correlation from other correlations for the three different flows. It was also shown that the SSG-RSTM high-Reynolds number turbulence model does not deal with the low-Prandtl number effect properly when the Peclet number is small. According to the present calculations for a parallel flow, all the old correlations do not match with the present numerical solutions and a new correlation is proposed. The correlations by Dwyer (1966, “Recent Developments in Liquid-Metal Heat Transfer,” At. Energy Rev., 4, pp. 3–92) for a cross flow and its modified correlation that takes into account of flow inclination for inclined flows work best and are accurate enough to be used for the design of the heat exchanger.

The Simulation Study of Turbulence Models for Conjugate Heat Transfer Analysis of a High Pressure Air-Cooled Gas Turbine

2010 ◽  
Author(s):  
Zhenfeng Wang ◽  
Peigang Yan ◽  
Hongfei Tang ◽  
Hongyan Huang ◽  
Wanjin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Turbulence Model ◽  
Conjugate Heat Transfer ◽  
Turbulence Models ◽  
Turbulence Characteristic ◽  
The Heat Transfer Coefficient

The different turbulence models are adopted to simulate NASA-MarkII high pressure air-cooled gas turbine. The experimental work condition is Run 5411. The paper researches that the effect of different turbulence models for the flow and heat transfer characteristics of turbine. The turbulence models include: the laminar turbulence model, high Reynolds number k-ε turbulence model, low Reynolds number turbulence model (k-ω standard format, k-ω-SST and k-ω-SST-γ-θ) and B-L algebra turbulence model which is adopted by the compiled code. The results show that the different turbulence models can give good flow characteristics results of turbine, but the heat transfer characteristics results are different. Comparing to the experimental results, k-ω-SST-θ-γ turbulence model results are more accurate and can simulate accurately the flow and heat transfer characteristics of turbine with transition flow characteristics. But k-ω-SST-γ-θ turbulence model overestimates the turbulence kinetic energy of blade local region and makes the heat transfer coefficient higher. It causes that local region temperature is higher. The results of B-L algebra turbulence model show that the results of B-L model are accurate besides it has 4% temperature error in the transition region. As to the other turbulence models, the results show that all turbulence models can simulate the temperature distribution on the blade pressure surface except the laminar turbulence model underestimates the heat transfer coefficient of turbulence flow region. On the blade suction surface with transition flow characteristics, high Reynolds number k-ε turbulence model overestimates the heat transfer coefficient and causes the blade surface temperature is high about 90K than the experimental result. Low Reynolds number k-ω standard format and k-ω-SST turbulence models also overestimate the blade surface temperature value. So it can draw a conclusion that the unreasonable choice of turbulence models can cause biggish errors for conjugate heat transfer problem of turbine. The combination of k-ω-SST-γ-θ model and B-L algebra model can get more accurate turbine thermal environment results. In addition, in order to obtain the affect of different turbulence models for gas turbine conjugate heat transfer problem. The different turbulence models are adopted to simulate the different computation mesh domains (First case and Second case). As to each cooling passages, the first case gives the wall heat transfer coefficient of each cooling passages and the second case considers the conjugate heat transfer course between the cooling passages and blade. It can draw a conclusion that the application of heat transfer coefficient on the wall of each cooling passages avoids the accumulative error. So, for the turbine vane geometry models with complex cooling passages or holes, the choice of turbulence models and the analysis of different mesh domains are important. At last, different turbulence characteristic boundary conditions of turbine inner-cooling passages are given and K-ω-SST-γ-θ turbulence model is adopted in order to obtain the effect of turbulence characteristic boundary conditions for the conjugate heat transfer computation results. The results show that the turbulence characteristic boundary conditions of turbine inner-cooling passages have a great effect on the conjugate heat transfer results of high pressure gas turbine.

Topology Optimization of Serpentine Channels for Minimization of Pressure Loss and Maximization of Heat Transfer Performance As Applied for Additive Manufacturing

2019 ◽  
Author(s):  
Shinjan Ghosh ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Topology Optimization ◽  
Additive Manufacturing ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Blade Cooling

Abstract Gas Turbine blade cooling is an important topic of research, as a high turbine inlet temperature (TIT) essentially means an increase in efficiency of gas turbine cycles. Internal cooling channels in gas turbine blades are key to the cooling and prevention of thermal failure of the material. Serpentine channels are a common feature in internal blade cooling. Optimization methods are often employed in the design of blade internal cooling channels to improve heat-transfer and reduce pressure drop. Topology optimization uses a variable porosity approach to manipulate flow geometries by adding or removing material. Such a method has been employed in the current work to modify the geometric configuration of a serpentine channel to improve total heat transferred and reduce the pressure drop. An in-house OpenFOAM solver has been used to create non-traditional geometries from two generic designs. Geometry-1 is a 2-D serpentine passage with an inlet and 4 bleeding holes as outlets for ejection into the trailing edge. Geometry-2 is a 3-D serpentine passage with an aspect ratio of 3:1 and consists of two 180-degree bends. The inlet velocity for both the geometries was used as 20 m/s. The governing equations employ a “Brinkman porosity parameter” to account for the porous cells in the flow domain. Results have shown a change in shape of the channel walls to enhance heat-transfer in the passage. Additive manufacturing can be employed to make such unconventional shapes.

Computation of flow and heat transfer through channels with periodic dimple/protrusion walls using low-Reynolds number turbulence models

2019 ◽  
Vol 29 (3) ◽  
pp. 1178-1207 ◽  
Author(s):  
Mohammad Fazli ◽  
Mehrdad Raisee
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Correction Term ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Internal Cooling ◽  
Recirculation Bubble ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Numerical Predictions

PurposeThis paper aims to predict turbulent flow and heat transfer through different channels with periodic dimple/protrusion walls. More specifically, the performance of various low-Rek-ε turbulence models in prediction of local heat transfer coefficient is evaluated.Design/methodology/approachThree low-Re numberk-εturbulence models (the zonalk-ε, the lineark-εand the nonlineark-ε) are used. Computations are performed for three geometries, namely, a channel with a single dimpled wall, a channel with double dimpled walls and a channel with a single dimple/protrusion wall. The predictions are obtained using an in house finite volume code.FindingsThe numerical predictions indicate that the nonlineark-εmodel predicts a larger recirculation bubble inside the dimple with stronger impingement and upwash flow than the zonal and lineark-εmodels. The heat transfer results show that the zonalk-εmodel returns weak thermal predictions in all test cases in comparison to other turbulence models. Use of the lineark-εmodel leads to improvement in heat transfer predictions inside the dimples and their back rim. However, the most accurate thermal predictions are obtained via the nonlineark-εmodel. As expected, the replacement of the algebraic length-scale correction term with the differential version improves the heat transfer predictions of both linear and nonlineark-εmodels.Originality/valueThe most reliable turbulence model of the current study (i.e. nonlineark-εmodel) may be used for design and optimization of various thermal systems using dimples for heat transfer enhancement (e.g. heat exchangers and internal cooling system of gas turbine blades).

A Study of Convective Heat Transfer and Pressure Drop Phenomena in Curved Microchannels

2010 ◽  
Author(s):  
Heng-Chih Tang ◽  
Tien-Chien Jen ◽  
Yi-Hsin Yen ◽  
Jyh-Tong Teng
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Cooling System ◽  
Outer Wall ◽  
Flow Patterns ◽  
Hydraulic Diameter ◽  
Main Stream ◽  
Dean Number

The research conducted in this paper was based on numerical simulation analysis that investigated the relationships between convective heat transfer and pressure drops and the flow patterns between conventional straight channels and curved microchannels. The main goal is to thoroughly investigate thermo-fluidic phenomena in curved microchannels and to determine the optimal design for the curved microchannel cooling system. Commercial numerical software (ESI-CFD) was used to simulate all cases studied in this paper. The computer simulated results were compared with actual experimental results to evaluate its accuracy. Six cases of different dimensions were studied. Results obtained from this study showed that when the dimensions of curved microchannels are smaller than 40 μm in height, conventional macro fluidic theory can still be used, since the numerically simulated results are in good agreement (<6% difference) with those obtained experimentally. Hydraulic diameter is the factor affects the pressure drop. Larger hydraulic diameter causes smaller pressure drop while smaller hydraulic diameter results in higher pressure drop. Secondary flow patterns and Nusselt numbers are also illustrated in this paper. When the Dean number is lower than 400, the pressure drop of fluid in 40 μm height models is similar to that found in straight microchannels. For the velocity profiles in the curved microchannels, the main stream is at the center of the curved microchannel first. But it is gradually offsets to the outer wall when the mass flow rates increases. The centrifugal force due to the curve geometry is the main reason that results in the shifting of the main flow toward the outer wall of the microchannel.

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics for Different Hole Geometries of a Turbine Casing Impingement Cooling System

2011 ◽  
Author(s):  
F. Ben Ahmed ◽  
R. Tucholke ◽  
B. Weigand ◽  
K. Meier
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling System ◽  
Ambient Air ◽  
Impinging Jets ◽  
Nozzle Geometry ◽  
Impingement Cooling ◽  
Pressure Losses ◽  
Aspect Ratios ◽  
Mach Numbers

A representative part of an active clearance control system for a low pressure turbine has been numerically investigated. The setup consisted of a cylindrical plenum with 20 inline arranged impinging jets at the bottom side discharging on a flat plate. The study focused on the influence of the nozzle geometry on the flow as well as heat transfer characteristics at the impingement plate and the discharge pressure drop. CFD (Computational Fluid Dynamics) simulations were performed for a constant Reynolds number ReD = 7,500 and different mean jet Mach numbers up to 0.7. Different length-to-diameter ratios of the jet holes (L/D) and various hole shapes (cylindrical, elliptic, convergent and divergent conical) were investigated to evaluate the performance of the impingement cooling configurations. The predictions showed a significant influence of the length-to-diameter ratio of the orifice bores on the heat transfer and the pressure losses. For L/D = 2 no suction of the ambient air in the nozzles was observed. In comparison to the configuration with L/D = 0.25 an improvement of the discharge coefficient of 9% for Ma = 0.7 and 20% for Ma = 0.17 was achieved. However, the highest heat transfer was observed for the smallest L/D-ratio of 0.25. The shape variation showed that only the elliptic jet holes with a ratio of AR = 0.5 enhanced the overall heat transfer and simultaneously reduced the pressure losses because of discharging onto the target plate. This result was found to be valid for all investigated jet Mach numbers. Additionally, for both elliptic jet aspect ratios of 0.5 and 2 the axis-switchover phenomenon of the flow was observed.

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