Flow Pattern and Heat Transfer in a Closed Rotating Annulus

1994 ◽  
Vol 116 (3) ◽  
pp. 542-547 ◽  
Author(s):  
D. Bohn ◽  
G. H. Dibelius ◽  
E. Deuker ◽  
R. Emunds
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Side Wall ◽  
Computer Code ◽  
Turbine Rotor ◽  
Base Case ◽  
Convection Flow ◽  
Coriolis Forces ◽  
R Ratio ◽  
Temperature Levels

The prediction of the temperature distribution in a gas turbine rotor containing gasfilled closed cavities, for example between two disks, has to account for the heat transfer conditions encountered inside these cavities. In an entirely closed annulus no forced convection is present, but a strong natural convection flow occurs induced by a nonuniform density distribution in the centrifugal force field. A computer code has been developed and applied to a rotating annulus with square cross section as a base case. The co-axial heat flux from one side wall to the other was modeled assuming constant temperature distribution at each wall but at different temperature levels. Additionally the inner and outer walls were assumed to be adiabatic. The code was first verified for the annulus approaching the plane square cavity in the gravitational field, i.e., the ratio of the radius r over the distance h between outer and inner cylindrical wall was set very large. The results obtained agree with De Vahl Davis’ benchmark solution. By reducing the inner radius to zero, the results could be compared with Chew’s computation of a closed rotating cylinder, and again good agreement was found. Parametric studies were carried out varying the Grashof number Gr, the rotational Reynolds number Re, and the r/h ratio, i.e., the curvature of the annulus. A decrease of this ratio at constant Gr and Re number results in a decrease of heat transfer due to the Coriolis forces attenuating the relative gas velocity. The same effect can be obtained by increasing the Re number with the h/r ratio and the Gr number being constant. By inserting radial walls into the cavity the influence of the Coriolis forces is reduced, resulting in an increase of heat transfer.

scholarly journals Flow Pattern and Heat Transfer in a Closed Rotating Annulus

1992 ◽  
Author(s):  
D. Bohn ◽  
G. H. Dibelius ◽  
E. Deuker ◽  
R. Emunds
Keyword(s):  
Heat Transfer ◽  
Side Wall ◽  
Computer Code ◽  
Turbine Rotor ◽  
Base Case ◽  
Convection Flow ◽  
Uniform Density ◽  
Coriolis Forces ◽  
R Ratio ◽  
Axial Heat

The prediction of the temperature distribution in a gas turbine rotor containing gas filled closed cavities, for example in between two discs, has to account for the heat transfer conditions encountered inside these cavities. In an entirely closed annulus no forced convection is present, but a strong natural convection flow occurs induced by a non-uniform density distribution in the centrifugal force field. A computer code has been developed and applied to a rotating annulus with square cross section as a base case. A co-axial heat flux from one side wall to the other was modelled assuming the temperatures at this walls being different but uniformly distributed, while both the outer and inner cylindrical surfaces were assumed to be adiabatic. The code was first verified for the annulus approaching the plane square cavity in the gravitational field, i.e. the ratio of the radius r over the distance h between outer and inner cylindrical wall was set very large. The results obtained agree with De Vahl Davis’ benchmark solution. By reducing the inner radius to zero, the results could be compared with Chew’s computation of a closed rotating cylinder, and again good agreement was found. Parametric studies were carried out varying the Grashof number Gr, the rotational Reynolds number Re and the r/h-ratio, i.e. the curvature of the annulus. A decrease of this ratio at constant Gr and Re number results in a decrease of heat transfer due to the Coriolis forces attenuating the relative gas velocity. The same effect can be obtained by increasing the Re number with the h/r-ratio and the Gr number being constant. By inserting radial walls into the cavity the influence of the Coriolis forces is reduced resulting in an increase of heat transfer.

scholarly journals Prediction of Unshrouded Rotor Blade Tip Heat Transfer

1995 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Stokes Equations ◽  
Space Shuttle ◽  
Suction Side ◽  
Computer Code ◽  
Turbine Rotor ◽  
High Rate ◽  
Blade Surface ◽  
Blade Tip

The rate of heat transfer on the tip of a turbine rotor blade and on the blade surface in the vicinity of the tip, was successfully predicted. The computations were performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations using an efficient multigrid method. The case considered for the present calculations was the SSME (Space Shuttle Main Engine) high pressure fuel side turbine. The predictions of the blade tip heat transfer agreed reasonably well with the experimental measurements using the present level of grid refinement. On the tip surface, regions with high rate of heat transfer was found to exist close to the pressure side and suction side edges. Enhancement of the heat transfer was also observed on the blade surface near the tip. Further comparison of the predictions was performed with results obtained from correlations based on fully developed channel flow.

High Rotation Number Heat Transfer of Rotating Trapezoidal Duct With 45-deg Staggered Ribs and Bleeds From Apical Side Wall

2007 ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Minn Liou ◽  
Shyr Fuu Chiou ◽  
Shuen Fei Chang
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Density Ratio ◽  
Side Wall ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Practical Applications ◽  
Turbine Rotor Blade ◽  
Apical Side

An experimental study of heat transfer in a radially rotating trapezoidal duct with two opposite walls roughened by 45° staggered ribs and mid-rib bleeds from the apical side wall is performed. Centerline heat transfer variations on two rib-roughened surfaces are measured for radially outward flows with and without bleeds at test conditions of Reynolds number (Re), rotation number (Ro) and density ratio (Δρ/ρ) in the ranges of 15000–30000, 0–0.8 and 0.04–0.31, respectively. Geometrical configurations and rotation numbers tested have considerably extended the previous experiences that offer practical applications to the trail edge cooling of a gas turbine rotor blade. A selection of experimental data illustrates the individual and interactive influences of Re, Ro and buoyancy number (Bu) on local heat transfer with and without bleeds. Local heat transfer results are generated with the influences of sidewall bleeds examined to establish heat transfer correlations with Re, Ro and Bu as the controlling flow parameters for design applications.

Estimation of Undisturbed Geothermal Gradient in Wells From Measured Drilling Data: A Numerical Approach

2017 ◽  
Author(s):  
Lucas Cantinelli Sevillano ◽  
Jesus De Andrade ◽  
Sigbjørn Sangesland
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Temperature Distribution ◽  
Oil And Gas ◽  
Drilling Fluid ◽  
Geothermal Gradient ◽  
Computer Code ◽  
Numerical Approach ◽  
Rock Properties ◽  
Drilling Fluids

The undisturbed geothermal gradient is a key thermal boundary that drives heat transfer processes occurring in oil and gas wells throughout their lifetime. However, the temperature distribution with depth is somewhat uncertain, and this is often assumed to be a linear approximation from the mudline to the bottom of the well. During drilling, the circulating temperature may significantly affect the rheology of the drilling fluids and the cement setting processes. Therefore, erroneous estimates of the wellbore temperature may affect the overall performance of the drilling phase and subsequent well operations. Further, it is important to know the accurate temperature distribution within the formation for assessment of the petroleum prospectivity through source rock maturation and reservoir quality. This paper presents a numerical methodology to estimate the undisturbed geothermal gradient while drilling in offshore wells. This methodology may also be applied to onshore wells by simplification. The new approach is based on an in-house axisymmetric wellbore transient thermal model, in which the equations are solved using the finite difference method. The model computes the heat transfer between the well and riser system with the surroundings. However, other computational codes may also be used following the framework presented in this study. The computer code should provide a detailed representation of the geometry of the wellbore, the physical properties of the drilling fluid and formation, the suitable thermal boundary conditions and temporal discretization. The temperatures of the fluid at the inlet of the drillstring and at the bottom hole assembly (BHA), in the annulus A, are used as input to the numerical model that iteratively adjusts the undisturbed geothermal gradient, which generated the temperature recordings while drilling. The paper comprises cases studies of hypothetical wells drilled in relevant offshore areas in the world, each with their distinctive and variable geothermal gradient, defined by the different rock formations encountered. Uncertainties regarding the thermal properties of the rock were also considered to ascertain the robustness of the code. The water depth of the drilling site was also observed to impact the convergence of the algorithm. The results obtained by the numerical approach are in good agreement with the expected values of the undisturbed formation temperatures. The novelty of the numerical framework is the ability to provide reliable and satisfactory estimates of the undisturbed geothermal gradient for wellbores with any configuration, lithology and rock properties. These estimates are based on temperature measurements of the circulating drilling fluid at the BHA and account for uncertainty in rock thermal properties; in reasonable time using standard engineering computers.

scholarly journals Analysis of Gas Turbine Rotor Blade Tip and Shroud Heat Transfer

1996 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Stokes Equations ◽  
Computer Code ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbine Rotor Blade ◽  
Blade Tip

Predictions of the rate of heat transfer to the tip and shroud of a gas turbine rotor blade are presented. The simulations are performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations. The effect of inlet boundary layer thickness as well as rotation rate on the tip and shroud heat transfer is examined. The predictions of the blade tip and shroud heat transfer are in reasonable agreement with the experimental measurements. Areas of large heat transfer rates are identified and physical reasoning for the phenomena presented.

Numerical study on free convection of cold water in a square porous cavity heated with sinusoidal wall temperature

2017 ◽  
Vol 27 (4) ◽  
pp. 1000-1014 ◽  
Author(s):  
K. Janagi ◽  
S. Sivasankaran ◽  
M. Bhuvaneswari ◽  
M. Eswaramurthi
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cold Water ◽  
Side Wall ◽  
Darcy Number ◽  
Density Inversion ◽  
Content Type ◽  
Density Inversion Parameter

Purpose The aim of the present study is to analyze the natural convection flow and heat transfer of cold water around °C in a square porous cavity. The horizontal walls of cavity are adiabatic, and the vertical walls are maintained at different temperatures. The right side wall is maintained at temperature θc, and the left side wall is maintained at sinusoidal temperature distribution. Design/methodology/approach The Brinkman–Forchheimer-extended Darcy model for porous medium is used to study the effects of density inversion parameter, Rayleigh number and impact of Darcy number and porosity. The finite volume method is used to solve the governing equations. Findings The heat transfer rate is increased on increasing the Darcy number and porosity. Also, the convective heat transfer rate is decreased first and then increased on increasing the density inversion parameter. Research limitations/implications The numerical computations have been carried out for the Darcy number ranging of 10(−4) ≤ Da ≤ 10(−1), the porosity ranging of 0.4 ≤ ε ≤ 0.8 and the density inversion parameter ranging of 0 ≤ Tm ≤ 1 and keeping Ra = 106. Practical implications The results can be used in the cooling of electronic components, thermal storage system and in heat exchangers. Originality/value The choice of consideration of sinusoidal heating and density maximum effect produces good result in flow field and temperature distribution. The obtained results can be used in various fields.

A Comparison of Computational and Experimental Results for Flow and Heat Transfer From an Array of Heated Blocks

1997 ◽  
Vol 119 (1) ◽  
pp. 32-39 ◽  
Author(s):  
A. M. Anderson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Control Volume ◽  
Computer Code ◽  
Experimental Results ◽  
Convection Flow ◽  
Channel Height ◽  
Computational Results ◽  
Adiabatic Wall ◽  
Flow And Heat Transfer

This paper summarizes computational results for flow and heat transfer over an array ofidealized electronic components and compares them to experimental data. The numerical modeling was performed using a commercial finite control volume computer code (Flotherm1, by Flomerics) and the results are compared to a set of experimental data. The experimental model consists of a uniform array of eight rows by six columns of solid aluminum blocks (9.5 mm high × 46.5 mm wide × 37.5 mm long) mounted on an adiabatic wall of a channel in forced convection flow. Four channel heights (H/B = 1.5–4.6) and a range of inlet velocities (3.0 to 8.1 m/s) were modelled. The flow was modeled as turbulent flow using the κ-ε turbulence model. Data for the adiabatic heat transfer coefficient had, the superposition kernel function g*, and the channel pressure drop ΔP are compared. The computational results for had are in excellent agreement with the experimental data (within about five percent on average). The computationalresults for g* predict the correct trends (roll off with downstream distance, channel height dependence, and velocity independence). However, values are as much as 50 percent higher than the experimental results which means the computational model under-predicts the amount of cross channel mixing. Computational results for ΔP compare reasonably well (within 20 percent on average).

Effect of Flow Exit Angle and Blade Height on the Temperature Distribution of a Typical Gas Turbine Rotor Blade

2012 ◽  
Vol 452-453 ◽  
pp. 502-506
Author(s):  
Esmail Poursaeidi ◽  
Maryam Mohammadi ◽  
Seyed Sina Khamesi
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transfer Rate ◽  
Direct Effect ◽  
Rotor Blade ◽  
Transfer Rate ◽  
Turbine Rotor ◽  
Exit Angle ◽  
Blade Height ◽  
Turbine Rotor Blade

One of the major factors which have important effects in turbine blade designing is temperature distribution and its heat transfer rate. The temperature distribution in blades depends on many factors; one of the most important ones is the geometry of the blades. In this paper by continuing some previous findings about the geometry[1], an optimized blade and a real one are compared from the thermally aspect view. Flow exit angle of the rotor blade and the blade height are two parameters which have direct effect on the heat transfer rate. The presented temperature distribution is solved based on the new flow exit angle of rotor blade. By optimizing the flow exit angle for the first time, the blade height is computed. By solving mathematically and thermodynamically relations and writing a solving code based on the finite volume method, the temperature and the heat transfer rate are computed numerically. These results shows the direct effect of flow exit angle on temperature distribution which can be used for upgrading the turbine efficiency.

Effect of Apex Angle, Porosity, and Permeability on Flow and Heat Transfer in Triangular Porous Ducts

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
S. Negin Mortazavi ◽  
Fatemeh Hassanipour
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Temperature Distribution ◽  
Apex Angle ◽  
Convection Flow ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Wide Range ◽  
Porosity And Permeability ◽  
Forced Convection Flow

This paper presents an analysis of forced convection flow and heat transfer in triangular ducts containing a porous medium. The porous medium is isotropic and the flow is laminar, fully developed with constant properties. Numerical results for velocity and temperature distribution (in dimensionless format) in the channel are presented for a wide range of porosity, permeability, and apex angles. The effects of apex angle and porous media properties (porosity and permeability) are demonstrated on the velocity and temperature distribution, as well as the friction factor (fRe) and Nusselt numbers in the channel for both Isoflux (NuH) and Isothermal (NuT) boundary conditions. The consistency of our findings has been verified with earlier results in the literature on empty triangular ducts, when the porosity in our models is made to approach one.

A Study on Cooling Characteristics of Thermoelectric Cooling System Using Thermoelectric Materials

2011 ◽  
Vol 264-265 ◽  
pp. 1770-1775
Author(s):  
Ho Dong Yang ◽  
Hee Sung Yoon ◽  
Yool Kwon Oh
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Piezoelectric Actuator ◽  
Thermoelectric Materials ◽  
Cooling System ◽  
Acoustic Streaming ◽  
Thermoelectric Module ◽  
Cooling Effect ◽  
Convection Flow ◽  
Thermoelectric Cooling

This study investigated on cooling characteristics of thermoelectric cooling system using thermoelectric materials as Bi-Te alloy. The thermoelectric module used as thermoelectric materials of thermoelectric cooling system can achieve heating and cooling by change of electricity direction. When thermoelectric module and cooling fan received 12V from DC power source, the cooling region was occurred in thermoelectric cooling system. Also, the piezoelectric actuator was applied to improve the cooling effect and investigate the heat transfer phenomenon. The temperature distribution of cooling region was measured to investigate cooling characteristics of thermoelectric cooling system. The flow phenomenon of cooling region was visualized using visualization device such as He-Ne laser, optical lens, image grabber and CCD camera. When the piezoelectric actuator was applied to the heat transfer process of thermoelectric cooling system, acoustic streaming was occurred in the cooling region. The acoustic streaming was occurred forced convection flow, and was regularly formed the temperature distribution in the cooling region. In the end, the results clearly show that the acoustic streaming is one of the prime effects to enhance the convection heat transfer and cooling effect.

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