The Effect of Diffusion Thermo and Thermal Diffusion for Helium Injection Into Plane and Axisymmetric Stagnation Flow of Air

1964 ◽  
Vol 86 (3) ◽  
pp. 311-319 ◽  
Author(s):  
E. M. Sparrow ◽  
W. J. Minkowycz ◽  
E. R. G. Eckert ◽  
W. E. Ibele
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusion ◽  
Free Stream ◽  
Appreciable Amount ◽  
Stagnation Flow ◽  
Adiabatic Wall ◽  
Helium Concentration ◽  
Aerospace Applications ◽  
Wide Range ◽  
Transfer Flow

An analysis has been carried out with the aim of clarifying the effects of diffusion thermo and thermal diffusion on heat transfer, flow, and mass transfer for the helium-air boundary layer in stagnation flow. To provide information applicable to both laboratory-type situations and aerospace applications, results have been obtained over the range of free-stream temperatures from 500 to 5000 deg R. For ratios of wall-to-stream temperature (Tw/Te) which differ only moderately from unity, it is found that the aforementioned diffusional transport has a decisive effect on heat transfer. For example, the heat transfer may be from the fluid to the wall even if Tw > Te. Further, the diffusion thermo is far more important than the thermal diffusion. When Tw/Te is much less than unity (highly cooled wall), the diffusional effects on heat transfer are small. For the condition of the adiabatic wall, the surface temperature (adiabatic wall temperature) can exceed that of the free stream by an appreciable amount. Once again, it is diffusion thermo which is responsible for this. Numerical results are given over a wide range of blowing rate for the Nusselt number, friction factor, and helium concentration at the wall.

Transpiration-Induced Buoyancy and Thermal Diffusion-Diffusion Thermo in a Helium-Air Free Convection Boundary Layer

1964 ◽  
Vol 86 (4) ◽  
pp. 508-514 ◽  
Author(s):  
E. M. Sparrow ◽  
W. J. Minkowycz ◽  
E. R. G. Eckert
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Diffusion ◽  
Energy Transport ◽  
Decisive Role ◽  
Stream Temperature ◽  
Horizontal Cylinder ◽  
Appreciable Amount ◽  
Convection Boundary Layer ◽  
Adiabatic Wall

A detailed analytical study has been carried out to examine the effects of buoyancy in a boundary layer where there is mass injection through a porous surface. Specific consideration is given to helium injection into air in the stagnation-point region of a horizontal cylinder. Mass and energy transport by thermal diffusion and diffusion thermo are also included in the analysis. It is found that both the transpiration-induced buoyancy and the diffusional transports play a decisive role in determining the heat transfer when the wall-to-stream temperature ratio (Tw/T∞) is only moderately different from unity. In particular, when Tw/T∞ > 1, the tendency of the transpiration-induced buoyancy to increase the heat transfer is opposed by the action of diffusion thermo. For the condition of the adiabatic wall, the wall temperature may exceed the stream temperature by an appreciable amount; this is due to diffusion thermo. The predictions of the analysis are compared with available experimental data.

scholarly journals Effect of Thermo Diffusion on Mass And Heat Transfer Flow on Convective Viscous Electrically Conducting Fluid Through a Porous Medium Bounded by a Semi-Infinite Vertical Plate with Variable Electrically Conductivity Diffusion Thermo Chemical Reaction

2019 ◽  
Vol 9 (1S5) ◽  
pp. 284-287
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusion ◽  
Diffusion Reaction ◽  
Element Analysis ◽  
Galerkin Finite Element ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid ◽  
Mass And Heat Transfer ◽  
Transfer Flow ◽  
Infinite Vertical Plate

In this paper we investigate thermochemical diffusion reaction and effects of thermal diffusion on the mass and heat transfer flux Although the effects of thermal diffusion are vast, they can be transmitted through a very wide medium.. By employing Galerkin-finite element analysis the equations solved with three nodded line segments

scholarly journals Turbulence Intensity, Length Scale, and Heat Transfer Around Stagnation Line of Cylinder and Model Blade

1999 ◽  
Author(s):  
V. P. Maslov ◽  
B. I. Mineev ◽  
K. N. Pichkov ◽  
A. N. Secundov ◽  
A. N. Vorobiev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Turbulence Models ◽  
Leading Edge ◽  
Circular Cylinders ◽  
Length Scale ◽  
Stagnation Line ◽  
Free Stream Turbulence ◽  
Wide Range

A hot-wire technique was used to measure turbulence characteristics in the vicinity of the stagnation line of circular cylinders and a turbine blade model (a chord length of 1 metre). Heat transfer intensity at the stagnation line of the cylinders was also measured by on-surface probes. The experiments were carried out in a wide range of the Reynolds number based on the blade leading edge/cylinder diameter, D (Re = 2.103–2.106) and integral length scale of free-stream turbulence, Le (Le = 0.1–10D) at two values of free stream turbulence intensity, Tu (Tu = 0.02 and 0.10). Along with the experimental data results of the 2D RANS computations are presented of the flow and heat transfer at the circular cylinder with the use of two turbulence models: a two-equation, k-ω SST, model of Menter, and a new two-equation, ν1-L, model developed in the course of the present study.

scholarly journals Effects of Leading-Edge Roughness on Fluid Flow and Heat Transfer in the Transitional Boundary Layer Over a Flat Plate

1994 ◽  
Author(s):  
Mark Pinson ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Stream ◽  
Turbine Blades ◽  
Leading Edge ◽  
Transition Process ◽  
Stanton Number ◽  
Edge Roughness ◽  
Wide Range ◽  
Edge Conditions

An experimental study was undertaken to gain insight into the physical mechanisms that affect the laminar-turbulent transition process downstream of the leading-edge roughness condition. Three sizes of sandpaper strips were chosen to simulate the randomly distributed roughness located near the leading edge of a turbine blade, and three sizes of cylinders were chosen to simulate the relatively isolated peak nature of the roughness structure. The roughness Reynolds numbers tested covered a wide range, from 2 to 2840. The roughness sizes were selected based on the measured roughness characteristics of used gas turbine blades. The results indicated that at low free-stream velocities (5 m/s), the maximum roughness height was the primary contributor to deviations from the undisturbed case. At higher free-stream velocities (5–7 m/s), three of the rough leading-edge conditions exhibited a dual-slope region between the laminar and turbulent Stanton number versus Reynolds number correlations. Analysis of the boundary layer indicated that the first segment of the dual-slope was laminar, but the wall heat transfer significantly deviates from the laminar correlation. The second segment was transitional. The dual-slope behavior and the waviness of the Stanton number distribution at higher free-stream velocities observed downstream of the rough leading-edge conditions are believed to have been caused by nonlinear amplification introduced by the finite disturbances at the leading edge.

The Use of CFD to Generate Heat Transfer Boundary Conditions for a Rotor-Stator Cavity in a Compressor Drum Thermal Model

2007 ◽  
Author(s):  
K. Saunders ◽  
S. Alizadeh ◽  
L. V. Lewis ◽  
J. Provins
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Boundary Conditions ◽  
Material Selection ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Adiabatic Wall ◽  
Test Information ◽  
Thermal Boundary Conditions ◽  
Wide Range

In an engine design process, thermo-mechanical analyses of compressor drums and casings are undertaken, to predict component temperatures and displacements, which are ultimately used for material selection, blade clearance control and lifing of components. The thermal boundary conditions are sourced from a small number of standard flow field and heat transfer solutions, leading to a reliance on engine thermocouple tests to provide calibration factors on the boundary conditions, which with changes in inlet flows and cavity geometry from the tested arrangements are unproven, limiting the ability to readacross the test information into new designs. Given that the thermal boundary conditions in compressor drum and casing components are largely driven by complex flow physics, in the absence of suitable test information, CFD methods can be used to provide boundary specification of the thermo-mechanical problem, incorporating the complex physics involved. Without the insight of the flow field solution in complex flow regions, specification of the boundary conditions is rather subjective and mostly based on intuition. This study shows the use of CFD to provide the boundary conditions for the rotor-stator cavity at the front of an IP compressor drum. The CFD is run adiabatically and through a set of unit heat transfer cases on separate sections of the cavity wall, at key points in the flight cycle. The analyses provide appropriately characterized thermal boundary conditions (specifically heat transfer coefficients and adiabatic wall temperatures) that are transferred into the thermo-mechanical model, which can then be run through a wide range of cycles without the need for further CFD calculations.

scholarly journals Heat Transfer Measurements on a Rotating Disk

1997 ◽  
Vol 3 (1) ◽  
pp. 1-9 ◽  
Author(s):  
G. Cardone ◽  
T. Astarita ◽  
G. M. Carlomagno
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Wall Temperature ◽  
Thermal Sensitivity ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
External Diameter ◽  
Adiabatic Wall ◽  
Good Spatial Resolution ◽  
Wide Range

Heat transfer to a rotating disk is measured for a wide range of Reynolds number values in the laminar, transitional and turbulent flow regimes. Measurements are performed by making use of the heated-thin-foil technique and by gauging temperature maps with an infrared scanning radiometer. The use of the IR radiometer is advantageous on account of its relatively good spatial resolution and thermal sensitivity and because it allows one to perform measurements down to very low local Reynolds numbers. Data is obtained on three disks, having an external diameter varying from 150mm to 450mm; the smallest disk is used only to measure the adiabatic wall temperature and can rotate up to 21,O00rpm. Heat transfer results are presented in terms of Nusselt and Reynolds numbers based on the local radius and show a substantial agreement with previous experimental and theoretical analyses. Transition to turbulent flow is found at aboutRe=250,000. A discussion about the role played by the adiabatic wall temperature is also included.

Magnetohydrodynamic Convective Heat and Mass Transfer Flow Due to a Rotating Disk With Thermal Diffusion Effect

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Kh. Abdul Maleque
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Differential Equations ◽  
Numerical Solution ◽  
Thermal Diffusion ◽  
Rotating Disk ◽  
Published Data ◽  
Convective Mass Transfer ◽  
Numerical Predictions ◽  
Transfer Flow

Considering the importance of mass transfer in a magnetohydrodynamic (MHD) convective flow, a numerical solution is obtained for a steady three-dimensional MHD convective mass transfer flow in an incompressible fluid due to a rotating disk with thermal diffusion. The governing partial differential equations of the MHD convective mass transfer flow are reduced to nonlinear ordinary differential equations by introducing suitable similarity transformations. The nonlinear similarity equations are then solved numerically by Nachtsheim–Swigert iteration technique. The results of the numerical solution are then presented graphically in the form of velocity, temperature, and concentration profiles. The corresponding skin-friction coefficients, the Nusselt number, and the Sherwood number are also calculated and displayed in tables showing the effects of various parameters on them. A good comparison between the present numerical predictions and the previously published data (Sparrow, and Gregg, 1959, “Heat Transfer From a Rotating Disk to Fluids of Any Prandtl Number,” ASME J. Heat Transfer, 8, pp. 249–251; Benton, 1966, “On the Flow Due to a Rotating Disc,” J. Fluid Mech., 24, pp. 781–800) has been achieved.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

Sign in / Sign up

Export Citation Format

Share Document