3D RANS Prediction of Gas-Side Heat Transfer Coefficients on Turbine Blade and Endwall

2011 ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Radial Profile ◽  
Turbulence Models ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Heat Transfer Coefficients ◽  
The Impact

This paper presents a study using 3D computational fluid dynamics (CFD) based on Reynolds-averaged Navier-Stokes (RANS) equations to predict turbine gas-side heat transfer coefficients (HTC) on the entire airfoil and endwall. The CFD results at different spanwise sections and endwall have been compared with the flat-plate turbulent boundary layer correlation and with the data in a NASA turbine rotor passage with strong secondary flows, under three different flow conditions. The enhancement effects of secondary flow vortices on the blade surface and endwall heat transfer rate have been examined in detail. Analyses were conducted for the impact of Reynolds number and exit Mach number on heat transfer. The SST, k-ε, V2F, and realizable k-ε turbulence models have been assessed. The classical log-law wall-functions have been found to be comparable to the wall-integration methods, but with much reduced sensitivity to inlet turbulence conditions. The migration of hot gas was simulated with a radial profile of inlet temperature. CFD results for mid-span HTCs of two other airfoils were also compared with test data. Overall results are encouraging and indicate improved HTC and temperature predictions from 3D CFD could help optimize the design of turbine cooling schemes.

Three-Dimensional RANS Prediction of Gas-Side Heat Transfer Coefficients on Turbine Blade and Endwall

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Radial Profile ◽  
Turbulence Models ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Heat Transfer Coefficients ◽  
The Impact

This paper presents a study using 3D computational fluid dynamics (CFD) based on Reynolds-averaged Navier-Stokes (RANS) equations to predict turbine gas-side heat transfer coefficients (HTC) on the entire airfoil and endwall. The CFD results at different spanwise sections and endwall have been compared with the flat-plate turbulent boundary layer correlation and with the data in a NASA turbine rotor passage with strong secondary flows, under three different flow conditions. The enhancement effects of secondary flow vortices on the blade surface and endwall heat transfer rate have been examined in detail. Analyses were conducted for the impact of Reynolds number and exit Mach number on heat transfer. The SST, k-ɛ, V2F, and realizable k-ɛ turbulence models have been assessed. The classical log-law wall-functions have been found to be comparable to the wall-integration methods but with much reduced sensitivity to inlet turbulence conditions. The migration of hot gas was simulated with a radial profile of inlet temperature. CFD results for mid-span HTCs of two other airfoils were also compared with test data. Overall, results are encouraging and indicate improved HTC and temperature predictions from 3D CFD could help optimize the design of turbine cooling schemes.

Thermal Validation of a Heat Shield Surface for a High Lift Blade Profile

2011 ◽  
Author(s):  
M. Cochet ◽  
W. Colban ◽  
M. Gritsch ◽  
S. Naik ◽  
M. Schnieder
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Heat Shield ◽  
Transfer Coefficients ◽  
High Lift ◽  
Heat Transfer Coefficients ◽  
Blade Tip ◽  
The Impact

Low emission requirements for heavy-duty gas turbines can be achieved with flat combustor temperature profiles, reducing the combustor peak temperature. As a result, the heat load on the first stage heat shield above the first stage blade increases. High lift airfoils cause increased thermal loading on the heat shield above the blade tip and impact the unavoidable secondary flows, including complex vortex flows. Cascade tests have been performed on a blade with a generic high lift profile and the results on the heat shield are presented. A transient thermochromic liquid crystal measurement technique was used to obtain heat transfer coefficients on the heat shield surface. Several variations of blade tip clearance were investigated, and the impact on heat transfer coefficients is shown. Computational fluid dynamics predictions are compared to the experimental data to interpret the data and validate the CFD.

Prediction of Velocities and Heat Transfer Coefficients in a Rotor-Stator Cavity

2004 ◽  
Author(s):  
Justin Evans ◽  
Lon M. Stevens ◽  
Clint Bodily ◽  
Moon-Kyoo Brian Kang
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Turbulence Models ◽  
Secondary Flows ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mesh Resolution ◽  
Convective Heat Transfer Coefficients

The calculation of swirl velocities and convective heat transfer coefficients in a rotor-stator cavity has been mostly based on equations taken from empirical data. However, the validity of these empirical relations is questionable in geometries and environments other than the specific ones for which they were derived. A commercial CFD code, Fluent, has been used to predict the swirl velocities and rotor disk convective heat transfer coefficient distribution for a rig at Arizona State University. The rig was run at several rotational Reynolds numbers (Reφ) varying from 4.6×105 to 8.6×105 and for various mass secondary flows. Several different turbulence models were used and the resulting predictions were compared with data obtained from the rig. Fluent was able to predict the swirl velocities, on average, within 30% and the convective heat transfer coefficients, on average, within 30% and often within 20%. The degree of agreement with the measured data was found to depend on which turbulence model that was used, mesh resolution, as well as the secondary flow and Reφ.

The Impact of Fin Deformation on Condensation Heat Transfer Coefficients in Internally Grooved Tubes

2013 ◽  
Author(s):  
Sunil Mehendale
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Thermal Contact ◽  
Heat Pumps ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Condensing Heat Transfer ◽  
The Impact ◽  
Tube Expansion

In HVACR equipment, internally enhanced round tube (microfin) designs such as axial, cross-grooved, helical, and herringbone are commonly used to enhance the boiling and condensing performance of evaporators, condensers, and heat pumps. Typically, such tubes are mechanically expanded by a mandrel into a fin pack to create an interference fit between the tube outside surface and the fin collar to minimize the thermal contact resistance between tube and fin. However, during this expansion process, the internal enhancements undergo varying amounts of deformation, which degrades the in-tube thermal performance. Extensive data on condensing heat transfer coefficients in microfin tubes have been reported in the open literature. However, researchers have seldom used expanded tubes to acquire and report such data. Hence, it is always questionable to use such pristine tube data for designing heat exchangers and HVACR systems. Furthermore, the HVACR industry has been experiencing steeply rising copper costs, and this trend is expected to continue in coming years. So, many equipment manufacturers and suppliers are actively converting tubes from copper to aluminum. However, because of appreciable differences between the material properties of aluminum and copper, as well as other manufacturing variables, such as mandrel dimensions, lubricant used, etc., tube expansion typically deforms aluminum fins more than copper fins. Based on an analysis of the surface area changes arising from tube expansion, and an assessment of the best extant in-tube condensation heat transfer correlations, this work proposes a method of estimating the impact of tube expansion on in-tube condensation heat transfer. The analysis leads to certain interesting and useful findings correlating fin geometry and in-tube condensation thermal resistance. This method can then be applied to more realistically design HVACR heat exchangers and systems.

Calculation of Disk Temperatures in Gas Turbine Rotor-Stator Cavities Using Conjugate Heat Transfer

2010 ◽  
Author(s):  
Aneesh Sridhar Vadvadgi ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Conjugate Heat Transfer ◽  
Computational Cost ◽  
Disk Surface ◽  
Turbine Rotor ◽  
Transfer Coefficients ◽  
Constant Wall Temperature ◽  
Heat Transfer Coefficients ◽  
Variable Surface

The present study deals with the numerical modeling of the turbulent flow in a rotor-stator cavity with or without imposed through flow with heat transfer. The commercial finite volume based solver, ANSYS/FLUENT is used to numerically simulate the problem. A conjugate heat transfer approach is used. The study specifically deals with the calculation of the heat transfer coefficients and the temperatures at the disk surfaces. Results are compared with data where available. Conventional approaches which use boundary conditions such as constant wall temperature or constant heat flux in order to calculate the heat transfer coefficients which later are used to calculate disk temperatures can introduce significant errors in the results. The conjugate heat transfer approach can resolve this to a good extent. It includes the effect of variable surface temperature on heat transfer coefficients. Further it is easier to specify more realistic boundary conditions in a conjugate approach since solid and the flow heat transfer problems are solved simultaneously. However this approach incurs a higher computational cost. In this study, the configuration chosen is a simple rotor and stator system with a stationary and heated stator and a rotor. The aspect ratio is kept small (around 0.1). The flow and heat transfer characteristics are obtained for a rotational Reynolds number of around 106. The simulation is performed using the Reynolds Stress Model (RSM). The computational model is first validated against experimental data available in the literature. Studies have been carried out to calculate the disk temperatures using conventional non-conjugate and full conjugate approaches. It has been found that the difference between the disk temperatures for conjugate and non-conjugate computations is 5 K for the low temperature and 30 K for the high temperature boundary conditions. These represent differences of 1% and 2% from the respective stator surface temperatures. Even at low temperatures, the Nusselt numbers at the disk surface show a difference of 5% between the conjugate and non-conjugate computations, and far higher at higher temperatures.

scholarly journals The Influence of Different Facings of Polyisocyanurate Boards on Heat Transfer through the Wall Corners of Insulated Buildings

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1991 ◽  
Author(s):  
Tomas Makaveckas ◽  
Raimondas Bliūdžius ◽  
Arūnas Burlingis
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Insulation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Thermal Bridge ◽  
Thermal Bridges ◽  
The Impact ◽  
Heat Flow Meter

Polyisocyanurate (PIR) thermal insulation boards faced with carboard, plastic, aluminum, or multilayer facings are used for thermal insulation of buildings. Facing materials are selected according to the conditions of use of PIR products. At the corners of the building where these products are joined, facings can be in the direction of the heat flux movement and significantly increase heat transfer through the linear thermal bridge formed in the connection of PIR boards with facing of both walls. Analyzing the installation of PIR thermal insulation products on the walls of a building, the structural schemes of linear thermal bridges were created, numerical calculations of the heat transfer coefficients of the linear thermal bridges were performed, and the influence of various facings on the heat transfer through the thermal bridge was evaluated. Furthermore, an experimental measurement using a heat flow meter apparatus was performed in order to confirm the results obtained by numerical calculation. This study provides more understanding concerning the necessity to evaluate the impact of different thermal conductivity facings on the heat transfer through corners of buildings insulated with PIR boards.

Multi-Jet Impingement Heat Transfer With a Dimple-Pimple Patterned Jet Plate

2020 ◽  
Author(s):  
Husam Zawati ◽  
Gaurav Gupta ◽  
Yakym Khlyapov ◽  
Erik Fernandez ◽  
Jayanta Kapat ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Underlying Mechanism ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Air Jets ◽  
Impingement Heat Transfer ◽  
Definition Of

Abstract The objective of the present study is the evaluation of the heat transfer difference between a novel jet plate configuration and a conventional flat jet orifice plate. Physical mechanisms that lead to a change in Nusselt number when comparing both configurations are discussed in two regions: impingement and crossflow. In the presented work, both plates with identical inline arrays of (20 × 26) circular air jets impinging orthogonally on a flat target comprised of 20 segments parallel to the jet orifice plates, are studied. The first is a staggered configuration of a pimple-dimple (convex-concave) plate. This plate features two jet diameters: (a) 4.63 mm emanating from negative sphere of 14.63 mm in radius inward imprint; (b) 2.19 mm emanating from a positive sphere of 17.07 mm in radius, protruding from the base of the plate. The second jet plate is flat, which serves as a baseline for the heat transfer study. This plate has a constant jet orifice diameters of 3.49 mm, found based on the definition of total average open area of the first plate (NPR configuration). Heat transfer characteristics and turbulent flow structures are investigated over jet-averaged Reynolds numbers (Reav,j) of 5,000, 7,000, and 9,000. Jet-to-plate distance (Z/Dj) is varied between (2.4 – 6.0) jet diameters. A numerical study is carried out to compare various turbulence models (κε-EB, κε-Lag EB, κε-v2f, κω-SST, RST). Numerical simulations are analyzed in detail to explain the underlying mechanism of heat transfer enhancement, related to such geometries. The convex-concaved plate yields lower globally-averaged heat transfer coefficients when compared to a flat jet plate in the impingement region. However, enhancement up to 23% is seen in the crossflow region, where the crossflow effects are dominant in a maximum-crossflow configuration.

Experimental and Numerical Study of Heat Transfer in a Gas Turbine Combustor Liner

2003 ◽  
Vol 125 (4) ◽  
pp. 994-1002 ◽  
Author(s):  
J. C. Bailey ◽  
J. Intile ◽  
T. F. Fric ◽  
A. K. Tolpadi ◽  
N. V. Nirmalan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Numerical Study ◽  
Cross Flow ◽  
Turbulence Models ◽  
Flow Distribution ◽  
Transfer Coefficients ◽  
Gas Turbine Combustor ◽  
Heat Transfer Coefficients ◽  
Combustor Liner

Experiments and numerical simulations were conducted to understand the heat transfer characteristics of a stationary gas turbine combustor liner cooled by impingement jets and cross flow between the liner and sleeve. Heat transfer was also aided by trip-strip turbulators on the outside of the liner and in the flowsleeve downstream of the jets. The study was aimed at enhancing heat transfer and prolonging the life of the combustor liner components. The combustor liner and flow sleeve were simulated using a flat-plate rig. The geometry has been scaled from actual combustion geometry except for the curvature. The jet Reynolds number and the mass-velocity ratios between the jet and cross flow in the rig were matched with the corresponding combustor conditions. A steady-state liquid crystal technique was used to measure spatially resolved heat transfer coefficients for the geometric and flow conditions mentioned above. The heat transfer was measured both in the impingement region as well as over the turbulators. A numerical model of the combustor test rig was created that included the impingement holes and the turbulators. Using CFD, the flow distribution within the flow sleeve and the heat transfer coefficients on the liner were both predicted. Calculations were made by varying the turbulence models, numerical schemes, and the geometrical mesh. The results obtained were compared to the experimental data and recommendations have been made with regard to the best modeling approach for such liner-flow sleeve configurations.

Transient Heat Transfer Experiments in Complex Passages

2005 ◽  
Author(s):  
Rico Poser ◽  
Jens von Wolfersdorf ◽  
Klaus Semmler
Keyword(s):  
Heat Transfer ◽  
Internal Heat ◽  
Direct Consequence ◽  
Data Evaluation ◽  
Transient Heat Transfer ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients ◽  
Blade Cooling

Transient heat transfer experiments were performed in a model of a multi-pass gas turbine blade cooling circuit. The inner surface of the Plexiglas model was coated with thermochromic liquid crystals in order to determine the internal heat transfer coefficients. A change in inlet temperature is applied using a pre-cooled heat exchanger. As for simple geometries the analytical solution of Fourier’s equation can often be directly used for data evaluation, one ought to pay attention to complex passages. The reason has to be seen that the flow in complex passages has to be characterized by local and time dependent fluid temperatures. As a direct consequence data evaluation might be limited to small evaluation areas especially far downstream. Otherwise the uncertainties in the heat transfer results will increase substantially. In the present study the sensitivity of the transient method for complex passages has been analyzed theoretically and applied experimentally.

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