Aero-Thermal Investigation of Convective and Radiative Heat Transfer on Active Clearance Control Manifolds

2019 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Operating Conditions ◽  
Impingement Heat Transfer ◽  
Blade Tip ◽  
Clearance Control

Abstract The present paper deals with the characterization of heat transfer on blade tip Active Clearance Control manifolds. Real engine geometries and operating conditions were considered in validated CFD computations to understand the impacts of both manifold surfaces convective and radiative heat transfer on the aero-thermal performance of the system. Different manifold geometries were accounted for also. The study sorted out that both the radiation and the convective heat transfer on the manifold surfaces are responsible of performance deteriorations as the impingement heat transfer on the casing is considered. The last evidence is motivated by the fresh fluid heat up along the feeding pipe. Radiative heat transfer from the casing to the manifold is found to be relevant, especially in case of high casing temperature or low undercowl flow rates. As a result of the study, is remarked that ACC manifold radiative and convective heat transfer should be considered for a proper system design.

Analysis of the Heat Transfer Mechanism in High-Temperature Circulating Fluidized Beds by a Numerical Model

2002 ◽  
Vol 124 (1) ◽  
pp. 34-39 ◽  
Author(s):  
Qiao He ◽  
Franz Winter ◽  
Ji-Dong Lu
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Radiative Heat Transfer ◽  
Fluidized Beds ◽  
Radiative Heat ◽  
Total Heat ◽  
Circulating Fluidized Beds ◽  
Total Heat Transfer

A general numerical model is presented here to describe the complex fluid dynamics and the heat transfer process in high-temperature circulating fluidized beds (CFBs). The core-wall concept is used to describe the gas-solid flow in the dilute phase section of CFBs. The variation of the thickness of the wall layer along the height direction is considered in the fluid dynamic model in order to approach the practical conditions. Three components of heat transfer, i.e., the particle-convective heat transfer, the gas-convective heat transfer, and the radiative heat transfer, and their contributions to the total heat transfer coefficient are investigated. The influences of some operating parameters on the total heat transfer and its components are predicted. Detailed information about the mechanism of heat transfer is discussed. The radiative heat transfer accounts for about 30∼60% of the total heat transfer in high temperature CFBs. It gradually increases along the height direction of the furnace. When the contribution of particle convection increases, the contribution of gas convection decreases, and vice versa. Particle size shows a significant effect on the radiative heat transfer and the convective heat transfer. High bed and wall temperatures will primarily increase the radiative heat transfer.

Effect of Variable Properties and Radiation on Convective Heat Transfer Measurements at Engine Conditions

2014 ◽  
Author(s):  
Nathan J. Greiner ◽  
Marc D. Polanka ◽  
James L. Rutledge ◽  
Andrew T. Shewhart
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Flat Plate ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Variable Properties ◽  
Radiative Component

Experiments measuring film cooling performance are often performed near room temperature over small ranges of driving temperature. For such experiments, fluid properties are nearly constant within the boundary layer and radiative heat transfer is negligible. Consequently, the heat flux to the wall is a linear function of driving temperature. Therefore, the convective heat transfer coefficient and adiabatic wall temperature can be extracted from heat flux measurements at two or more driving temperatures. For large driving temperatures, like those seen in gas turbine engines, significant property variations exist within the boundary layer. In addition, radiative heat transfer becomes sufficiently large such that it can no longer be neglected. As a result, heat flux becomes a non-linear function of driving temperature. Thus, for these high temperature cases, ambient temperature methods utilizing a linear heat flux assumption cannot be employed to characterize the convective heat transfer. The present study experimentally examines the non-linearity of heat flux for large driving temperatures flowing over a flat plate. The results are first used to validate the temperature ratio method presented in a previous study to account for variable properties within a boundary layer. This validation highlighted the need to account for the radiative component of the overall heat transfer. A method is subsequently proposed to account for the effects of both variable properties and radiation simultaneously. Finally, the method is validated with the experimental data. While this methodology was developed in a flat plate rig, it is applicable to any relevant configuration in a hot environment. The method is general and independent of the overall radiative component magnitude and direction. Overall, the technique provides a means of quantifying the impact of both variable properties and the radiative flux on the conductive heat transfer to or from a surface in a single experiment.

Modeling of Turbulent Combustion and Radiative Heat Transfer in a Object-Oriented CFD Code for Gas Turbine Application

2008 ◽  
Author(s):  
Antonio Andreini ◽  
Matteo Cerutti ◽  
Bruno Facchini ◽  
Luca Mangani
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Radiative Heat Transfer ◽  
Turbulent Combustion ◽  
Radiative Heat ◽  
Object Oriented ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Combustion Models

One of the driving requirements in gas turbine design is the combustion analysis. The reduction of exhaust pollutant emissions is in fact the main design constraint of modern gas turbine engines, requiring a detailed investigation of flame stabilization criteria and temperature distribution within combustion chamber. At the same time, the prediction of thermal loads on liner walls continues to represent a critical issue especially with diffusion flame combustors which are still widely used in aeroengines. To meet such requirement, design techniques have to take advantage also of the most recent CFD tools that have to supply advanced combustion models according to the specific application demand. Even if LES approach represents a very accurate approach for the analysis of reactive flows, RANS computation still represents a fundamental tool in industrial gas turbine development, thanks to its optimal tradeoff between accuracy and computational costs. This paper describes the development and the validation of both combustion and radiation models in a object-oriented RANS CFD code: several turbulent combustion models were considered, all based on a generalized presumed PDF flamelet approach, valid for premixed and non premixed flames. Concerning radiative heat transfer calculations, two directional models based on the P1-Approximation and the Finite Volume Method were treated. Accuracy and reliability of developed models have been proved by performing several computations on well known literature test-cases. Selected cases investigate several turbulent flame types and regimes allowing to prove code affordability in a wide range of possible gas turbine operating conditions.

Two-Dimensional Heat Transfer Distribution of a Rotating Ribbed Channel at Different Reynolds Numbers

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Ignacio Mayo ◽  
Tony Arts ◽  
Ahmed El-Habib ◽  
Benjamin Parres
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotation Number ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Flux Boundary Condition

The convective heat transfer distribution in a rib-roughened rotating internal cooling channel was measured for different rotation and Reynolds numbers, representative of engine operating conditions. The test section consisted of a channel of aspect ratio equal to 0.9 with one wall equipped with eight ribs perpendicular to the main flow direction. The pitch to rib height ratio was 10 and the rib blockage was 10%. The test rig was designed to provide a uniform heat flux boundary condition over the ribbed wall, minimizing the heat transfer losses and allowing temperature measurements at significant rotation rates. Steady-state liquid crystal thermography (LCT) was employed to quantify a detailed 2D distribution of the wall temperature, allowing the determination of the convective heat transfer coefficient along the area between the sixth and eighth rib. The channel and all the required instrumentation were mounted on a large rotating disk, providing the same spatial resolution and measurement accuracy as in a stationary rig. The assembly was able to rotate both in clockwise and counterclockwise directions, so that the investigated wall was acting either as leading or trailing side, respectively. The tested Reynolds number values (based on the hydraulic diameter of the channel) were 15,000, 20,000, 30,000, and 40,000. The maximum rotation number values were ranging between 0.12 (Re = 40,000) and 0.30 (Re = 15,000). Turbulence profiles and secondary flows modified by rotation have shown their impact not only on the average value of the heat transfer coefficient but also on its distribution. On the trailing side, the heat transfer distribution flattens as the rotation number increases, while its averaged value increases due to the turbulence enhancement and secondary flows induced by the rotation. On the leading side, the secondary flows counteract the turbulence reduction and the overall heat transfer coefficient exhibits a limited decrease. In the latter case, the secondary flows are responsible for high heat transfer gradients on the investigated area.

Radiative and Convective Conducting Fins on a Plane Wall, Including Mutual Irradiation

1971 ◽  
Vol 93 (1) ◽  
pp. 41-46 ◽  
Author(s):  
R. C. Donovan ◽  
W. M. Rohrer
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Considerable Increase ◽  
Radiative Heat ◽  
Plane Surface ◽  
Heat Fluxes ◽  
Fluid Medium ◽  
Radiant Exchange ◽  
Radiative Component

The radiative and convective heat transfer from a fin array consisting of longitudinal rectangular fins on a plane surface has been theoretically investigated by mathematically describing the interaction among the heat conduction in the fin, the convective heat transfer to the fluid medium, and the radiant exchange of the fin with the neighboring elements. Solutions for the fin temperature distribution, the local radiative heat fluxes over the fin and base surfaces, the total radiative heat transfer, the total convective heat transfer, and the effectiveness of the fins were found. In the primary range of physical interest, the fins usually cause a considerable increase in the convective component of the heat transfer but either cause decreases or only slight increases in the radiative component. Thus convection is generally the more effective mode of heat transfer in fin arrays, and the effectiveness of the fins decreases as the radiative component increases.

scholarly journals GENERAL MODEL OF RADIATIVE AND CONVECTIVE HEAT TRANSFER IN BUILDINGS: PART I: ALGEBRAIC MODEL OF RADIATIVE HEAT TRANSFER

2019 ◽  
Vol 59 (3) ◽  
pp. 211-223
Author(s):  
Tomáš Ficker
Keyword(s):  
Heat Transfer ◽  
Convective Heat ◽  
Radiative Heat Transfer ◽  
General Model ◽  
Radiative Heat ◽  
Algebraic Method ◽  
Algebraic Model ◽  
Thermal Engineering ◽  
Algebraic Equations ◽  
Wide Range

Radiative heat transfer is the most effective mechanism of energy transport inside buildings. One of the methods capable of computing the radiative heat transport is based on the system of algebraic equations. The algebraic method has been initially developed by mechanical engineers for wide range of thermal engineering problems. The first part of the present serial paper describes the basic features of the algebraic model and illustrates its applicability in the field of building physics. The computations of radiative heat transfer both in building enclosures and also in open building envelopes are discussed and their differences explained. The present paper serves as a preparation stage for the development of a more general model evaluating heat losses of buildings. The general model comprises both the radiative and convective heat transfers and is presented in the second part of this serial contribution.

Computational modelling of convective heat transfer in a simulated engine cooling gallery

2007 ◽  
Vol 221 (9) ◽  
pp. 1147-1157 ◽  
Author(s):  
K Robinson ◽  
M Wilson ◽  
M J Leathard ◽  
J G Hawley
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Computational Study ◽  
Convective Heat Transfer Coefficient ◽  
Computational Modelling ◽  
Operating Conditions ◽  
Ic Engine ◽  
Engine Cooling ◽  
Cfd Models

Experimental data from internal combustion (IC) engines suggests that the use of proprietary computational fluid dynamics (CFD) codes for the prediction of coolant-side heat transfer within IC engine coolant jackets often results in underprediction of the convective heat transfer coefficient. An experimental and computational study, based on a coolant gallery simulator rig designed specifically to reproduce realistic IC engine operating conditions, has been conducted to explore this issue. It is shown that the standard ‘wall function’ approach normally used in CFD models to model near-wall conditions does not adequately represent some features of the flow that are relevant in convective heat transfer. Alternative modelling approaches are explored to account for these shortcomings and an empirical approach is shown to be successful; however, the methodology is not easily transferable to other situations.

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