Flow and Heat Transfer in an Industrial Rotor-Stator Rim Sealing Cavity

2000 ◽  
Vol 124 (1) ◽  
pp. 125-132 ◽  
Author(s):  
A. V. Mirzamoghadam ◽  
Z. Xiao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Steady State ◽  
Wall Temperature ◽  
Thermal Model ◽  
Labyrinth Seal ◽  
Two Dimensional ◽  
Cfd Model ◽  
Flow And Heat Transfer

Flow and heat transfer in the row-1 upstream rotor-stator disk cavity of a large 3600-rpm industrial gas turbine was investigated using an integrated approach. A two dimensional axisymmetric transient thermal analysis using aeroengine-based correlations was performed to predict the steady-state metal temperatures and hot running seal clearances at ISO rated power condition. The cooling mass flow and the flow pattern assumption for the thermal model were obtained from the steady-state two dimensional axisymmetric CFD study. The CFD model with wall heat transfer was validated using cavity steady-state air temperatures and static pressures measured at inlet to the labyrinth seal and four cavity radial positions in an engine test which included the mean annulus static pressure at hub radius. The predicted wall temperature distribution from the matched thermal model was used in the CFD model by incorporating wall temperature curve-fit polynomial functions. Results indicate that although the high rim seal effectiveness prevents ingestion from entering the cavity, the disk pumping flow draws air from within the cavity to satisfy entrainment leading to an inflow along the stator. The supplied cooling flow exceeds the minimum sealing flow predicted from both the rotational Reynolds-number-based correlation and the annulus Reynolds number correlation. However, the minimum disk pumping flow was found to be based on a modified entrainment expression with a turbulent flow parameter of 0.08. The predicted coefficient of discharge (Cd) of the industrial labyrinth seal from CFD was confirmed by modifying the carryover effect of a correlation reported recently in the literature. Moreover, the relative effects of seal windage and heat transfer were obtained and it was found that contrary to what was expected, the universal windage correlation was more applicable than the aeroengine-based labyrinth seal windage correlation. The CFD predicted disk heat flux profile showed reasonably good agreement with the free disk calculated heat flux. The irregular cavity shape and high rotational Reynolds number (in the order of 7×107) leads to entrance effects that produce a thicker turbulent boundary layer profile compared to that predicted by the 1/7 power velocity profile assumption.

Flow and Heat Transfer in an Industrial Rotor-Stator Rim Sealing Cavity

2000 ◽  
Author(s):  
Alexander V. Mirzamoghadam ◽  
Zhenhua Xiao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Steady State ◽  
Wall Temperature ◽  
Thermal Model ◽  
Labyrinth Seal ◽  
Cfd Model ◽  
Flow And Heat Transfer ◽  
Aero Engine

Flow and heat transfer in the row-1 upstream rotor-stator disc cavity of a large 3600-rpm industrial gas turbine was investigated using an integrated approach. A 2D axisymmetric transient thermal analysis using aero engine-based correlations was performed to predict the steady state metal temperatures and hot running seal clearances at ISO rated power condition. The cooling mass flow and the flow pattern assumption for the thermal model were obtained from the steady state 2D axisymmetric CFD study. The CFD model with wall heat transfer was validated using cavity steady state air temperatures and static pressures measured at inlet to the labyrinth seal and four cavity radial positions in an engine test which included the mean annulus static pressure at hub radius. The predicted wall temperature distribution from the matched thermal model was used in the CFD model by incorporating wall temperature curve-fit polynomial functions. Results indicate that although the high rim seal effectiveness prevents ingestion from entering the cavity, the disc pumping flow draws air from within the cavity to satisfy entrainment leading to an inflow along the stator. The supplied cooling flow exceeds the minimum sealing flow predicted from both the rotational Reynolds number-based correlation and the annulus Reynolds number correlation. However, the minimum disc pumping flow was found to be based on a modified entrainment expression with a turbulent flow parameter of 0.08. The predicted coefficient of discharge (Cd) of the industrial labyrinth seal from CFD was confirmed by modifying the carry-over effect of a correlation reported recently in the literature. Moreover, the relative effects of seal windage and heat transfer were obtained and it was found that contrary to what was expected, the universal windage correlation was more applicable than the aero engine-based labyrinth seal windage correlation. The CFD predicted disc heat flux profile showed reasonably good agreement with the free disc calculated heat flux. The irregular cavity shape and high rotational Reynolds number (in the order of 7×107) leads to entrance effects that produce a thicker turbulent boundary layer profile compared to that predicted by the 1/7 power velocity profile assumption.

Axisymmetric Stagnation—Point Flow and Heat Transfer of a Viscous Fluid on a Rotating Cylinder With Time-Dependent Angular Velocity and Uniform Transpiration

2006 ◽  
Vol 129 (1) ◽  
pp. 106-115 ◽  
Author(s):  
A. B. Rahimi ◽  
R. Saleh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Angular Velocity ◽  
Stokes Equations ◽  
Time Dependent ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer ◽  
Self Similar

The unsteady viscous flow and heat transfer in the vicinity of an axisymmetric stagnation point of an infinite rotating circular cylinder with transpiration U0 are investigated when the angular velocity and wall temperature or wall heat flux all vary arbitrarily with time. The free stream is steady and with a strain rate of Γ. An exact solution of the Navier-Stokes equations and energy equation is derived in this problem. A reduction of these equations is obtained by the use of appropriate transformations for the most general case when the transpiration rate is also time-dependent but results are presented only for uniform values of this quantity. The general self-similar solution is obtained when the angular velocity of the cylinder and its wall temperature or its wall heat flux vary as specified time-dependent functions. In particular, the cylinder may rotate with constant speed, with exponentially increasing/decreasing angular velocity, with harmonically varying rotation speed, or with accelerating/decelerating oscillatory angular speed. For self-similar flow, the surface temperature or its surface heat flux must have the same types of behavior as the cylinder motion. For completeness, sample semi-similar solutions of the unsteady Navier-Stokes equations have been obtained numerically using a finite-difference scheme. Some of these solutions are presented for special cases when the time-dependent rotation velocity of the cylinder is, for example, a step-function. All the solutions above are presented for Reynolds numbers, Re=Γa2∕2υ, ranging from 0.1 to 1000 for different values of Prandtl number and for selected values of dimensionless transpiration rate, S=U0∕Γa, where a is cylinder radius and υ is kinematic viscosity of the fluid. Dimensionless shear stresses corresponding to all the cases increase with the increase of Reynolds number and suction rate. The maximum value of the shear stress increases with increasing oscillation frequency and amplitude. An interesting result is obtained in which a cylinder rotating with certain exponential angular velocity function and at particular value of Reynolds number is azimuthally stress-free. Heat transfer is independent of cylinder rotation and its coefficient increases with the increasing suction rate, Reynolds number, and Prandtl number. Interesting means of cooling and heating processes of cylinder surface are obtained using different rates of transpiration.

Numerical Study of the Effects of Different Buoyancy Models on Supercritical Flow and Heat Transfer

2013 ◽  
Author(s):  
X. Y. Xu ◽  
T. Ma ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Enhancement ◽  
Wall Temperature ◽  
Mass Flux ◽  
Wall Heat Flux ◽  
Turbulent Heat ◽  
Transfer Enhancement ◽  
Temperature Prediction ◽  
Flow And Heat Transfer

Due to the dramatic changes in physical properties, the flow and heat transfer in supercritical fluid are significantly affected by buoyancy effects, especially when the ratio of inlet mass flux and wall heat flux is relatively small. In this study, the heat transfer of supercritical water in uniformly heated vertical tube is numerically investigated with different buoyancy models which are based on different calculation methods of the turbulent heat flux. The applicabilities of these buoyancy models are analyzed both in heat transfer enhancement and deterioration conditions. The simulation results show that these buoyancy models make few differences and give good wall temperature prediction in heat transfer enhancement condition when the ratio of inlet mass flux and wall heat flux is very small. With the increase of wall heat flux, the accuracy of wall temperature prediction reduces, and the differences between these buoyancy models become larger. No buoyancy model can currently make accurate wall temperature prediction in deterioration condition in this study.

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

2010 ◽  
Author(s):  
Tarek M. Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.

Starting Flow and Heat Transfer Downstream of a Backward-Facing Step

1991 ◽  
Vol 113 (3) ◽  
pp. 583-589 ◽  
Author(s):  
F. K. Tsou ◽  
Shih-Jiun Chen ◽  
Win Aung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady State ◽  
Shear Layer ◽  
Characteristic Time ◽  
Free Shear Layer ◽  
Hot Wire ◽  
Backward Facing Step ◽  
Flow And Heat Transfer ◽  
Hot Wire Anemometry

Experiments are performed to study the starting process of heat transfer downstream of a backward-facing step. A Ludwieg tube wind tunnel is employed to produce the incompressible flow, which accelerates from a zero velocity to a steady state value with an accelerating period of 7 ms and a steady-state period of 12 ms. Hot-wire anemometry and heat flux gages are used to measure the flow and heat transfer history, respectively. The onset of transition in the free shear layer shows that the disturbance originates from the top corner of the step, then propagating to the free stream. The velocity and turbulence profiles in the free shear layer reach steady-state values after the leading edge disturbance traverses to the measurement locations. In regions upstream and far downstream of the step, heat flux history data suggest the transformation of the flow from laminar to transitional and finally to turbulent flow. Hot-wire anemometry measurements indicate high-frequency turbulence with a short characteristic time. In the recirculating region, however, a longer characteristic time is observed because of the existence of large-scale eddies. The dimensionless reattachment length (xr/H) is shown to increase with time from the bottom corner (xr/H = 0) in the laminar regime to a maximum value of 13.6 in the transitional regime, and decreases to a constant values of 7.6 in the turbulent regime. The steady-state flow field and heat transfer compare favorably with existing data obtained using steady-state techniques.

scholarly journals Flow and heat transfer near a cylinders row

2021 ◽  
Vol 2039 (1) ◽  
pp. 012021
Author(s):  
A V Mityakov ◽  
A A Gusakov ◽  
M A Grekov ◽  
V V Seroshtanov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Flow Mode ◽  
Point Location ◽  
Heat Transfer Mode ◽  
Thickness Change ◽  
Transfer Mode ◽  
Flow Parameters ◽  
Flow And Heat Transfer

Abstract The paper aims to investigate the dependence of heat transfer classification on the Reynolds number (Re) during flow around circular heated cylinders row. The investigated range of Re number varies from 4.5×103 up to 42×103. The distance between cylinders S was changed from 0.5d to 4d (where d is the cylinders dia). Cylinders surface temperature was kept constant. For each Re number, the case when the cylinders were mounted one after the other was investigated. To measure heat transfer and flow parameters (velocity, heat flux and heat transfer coefficient) near and at the cylinders surface, two experimental methods were used: gradient heatmetry and PIV. Heat flux and velocity fields were obtained from gradient heatmetry and PIV results, based on which the flow mode could be determined and compared with heat transfer mode. As a result, it was found that heat transfer is influenced by both the Reynolds number and the distance between the cylinders. The observed features are associated with influence on characteristics such as separation point location, boundary layer thickness, change in flow between the cylinders and vortices formation.

scholarly journals Optimal heat transfer enhancement in plane Couette flow

2017 ◽  
Vol 835 ◽  
pp. 1157-1198 ◽  
Author(s):  
Shingo Motoki ◽  
Genta Kawahara ◽  
Masaki Shimizu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Three Dimensional ◽  
Wall Heat Flux ◽  
Scalar Dissipation ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Optimal State

Optimal heat transfer enhancement has been explored theoretically in plane Couette flow. The vector field (referred to as the ‘velocity’) to be optimised is time independent and divergence free, and temperature is determined in terms of the velocity as a solution to an advection-diffusion equation. The Prandtl number is set to unity, and consistent boundary conditions are imposed on the velocity and the temperature fields. The excess of a wall heat flux (or equivalently total scalar dissipation) over total energy dissipation is taken as an objective functional, and by using a variational method the Euler–Lagrange equations are derived, which are solved numerically to obtain the optimal states in the sense of maximisation of the functional. The laminar conductive field is an optimal state at low Reynolds number $Re\sim 10^{0}$. At higher Reynolds number $Re\sim 10^{1}$, however, the optimal state exhibits a streamwise-independent two-dimensional velocity field. The two-dimensional field consists of large-scale circulation rolls that play a role in heat transfer enhancement with respect to the conductive state as in thermal convection. A further increase of the Reynolds number leads to a three-dimensional optimal state at $Re\gtrsim 10^{2}$. In the three-dimensional velocity field there appear smaller-scale hierarchical quasi-streamwise vortex tubes near the walls in addition to the large-scale rolls. The streamwise vortices are tilted in the spanwise direction so that they may produce the anticyclonic vorticity antiparallel to the mean-shear vorticity, bringing about significant three-dimensionality. The isotherms wrapped around the tilted anticyclonic vortices undergo the cross-axial shear of the mean flow, so that the spacing of the wrapped isotherms is narrower and so the temperature gradient is steeper than those around a purely streamwise (two-dimensional) vortex tube, intensifying scalar dissipation and so a wall heat flux. Moreover, the tilted anticyclonic vortices induce the flow towards the wall to push low- (or high-) temperature fluids on the hot (or cold) wall, enhancing a wall heat flux. The optimised three-dimensional velocity fields achieve a much higher wall heat flux and much lower energy dissipation than those of plane Couette turbulence.

Buoyant Flow and Heat Transfer in a Conducting Baffle

2008 ◽  
Author(s):  
S. K. S. Boetcher ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Quasi Steady State ◽  
Two Dimensional ◽  
Buoyant Flow ◽  
Transfer Rates ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers ◽  
Negatively Buoyant ◽  
Surrounding Fluid

A numerical simulation of transient two-dimensional negatively buoyant flow into a straight baffle situated below an isothermal circular cylinder is performed. Both an adiabatic and a highly conducting baffle are considered over a range of Rayleigh numbers, 106 < RaD < 107. During the quasi-steady-state period, the surrounding fluid is effectively considered infinite in extent and at constant temperature. It is found that in general, the conducting baffle is at a disadvantage in maintaining a short attachment length which is needed to optimally slow the flow to prevent mixing. Qualitative flow fields are shown and heat transfer rates to the cylinder are calculated at the quasi-steady state.

Two Dimensional Simulation of Flow and Heat Transfer Characteristics of Turbulent Jets

2010 ◽  
Author(s):  
Tarek Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Jets ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Dimensional Simulation

In this study, flow and heat transfer characteristics of two-dimensional impinging jets are investigated numerically. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume CFD code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results show that the Reynolds number has significant effect on the heat transfer rate and has no effect on the location of the maximum Nusselt number.

scholarly journals RANS Simulation of the Effect of Pulse Form on Fluid Flow and Convective Heat Transfer in an Intermittent Round Jet Impingement

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 4025
Author(s):  
M. A. Pakhomov ◽  
V. I. Terekhov
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Steady State ◽  
Jet Impingement ◽  
Pulse Frequency ◽  
Steady State Flow ◽  
Pulsed Jet ◽  
Flow And Heat Transfer ◽  
Pulse Form

The of effect pulse form (rectangular, sinusoidal and triangular) on the fluid flow and heat transfer of an intermittent jet impingement was studied numerically. It was shown in a non-steady-state jet, both an increase and decrease in heat transfer are possible compared with steady-state jet for all investigated pulse forms. For small distances between the pipe edge and obstacle (H/D ≤ 6) in the pulsed jet, heat transfer around the stagnation point increases with increasing pulse frequency, while for H/D > 8 an increase in frequency causes a heat transfer decrease. A growth in the Reynolds number causes a decrease in heat transfer, and data for all frequencies approach the steady-state flow regime. The numerical model is compared with the experimental results. Satisfactory agreement on the influence of the form and frequency of pulses on heat transfer for the pulsed jet on the obstacle surface is obtained.

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