Numerical Predictions of the Effect of Rotation on Fluid Flow and Heat Transfer in an Engine-Similar Two-Pass Internal Cooling Channel With Smooth and Ribbed Walls

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
M. Schüler ◽  
H.-M. Dreher ◽  
S. O. Neumann ◽  
B. Weigand ◽  
M. Elfert
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Field ◽  
Secondary Flow ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Flow And Heat Transfer ◽  
Smooth Channel ◽  
Secondary Flow Field

In the present study, a two-pass internal cooling channel with engine-similar cross-sections was investigated numerically. The channel featured a trapezoidal inlet pass, a sharp 180 deg bend, and a nearly rectangular outlet pass. Calculations were done for a configuration with smooth walls and walls equipped with 45 deg skewed ribs (P/e=10, e/dh=0.1) at a Reynolds number of Re=50,000. The present study focused on the effect of rotation on fluid flow and heat transfer. The investigated rotation numbers were Ro=0.0 and 0.10. The computations were performed by solving the Reynolds-averaged Navier–Stokes equations (Reynolds-averaged Navier–Stokes method) with the commercial finite-volume solver FLUENT using a low-Re shear stress transport (SST) k-ω turbulence model. The numerical grids were block-structured hexahedral meshes generated with POINTWISE. Flow field measurements were independently performed at German Aerospace Centre Cologne using particle image velocimetry. In the smooth channel, rotation had a large impact on secondary flows. Especially, rotation induced vortices completely changed the flow field. Rotation also changed flow impingement on the tip and the outlet pass sidewall. Heat transfer in the outlet pass was strongly altered by rotation. In contrast to the smooth channel, rotation showed less influence on heat transfer in the ribbed channel. This is due to a strong secondary flow field induced by the ribs. However, in the outlet pass, Coriolis forces markedly affected the rib induced secondary flow field. The influence of rotation on heat transfer was visible in particular in the bend region and in the second pass directly downstream of the bend.

Numerical Predictions of the Effect of Rotation on Fluid Flow and Heat Transfer in an Engine-Similar Two-Pass Internal Cooling Channel With Smooth and Ribbed Walls

2010 ◽  
Author(s):  
M. Schu¨ler ◽  
H.-M. Dreher ◽  
S. O. Neumann ◽  
B. Weigand ◽  
M. Elfert
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Field ◽  
Secondary Flow ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Smooth Channel ◽  
Secondary Flow Field

In the present study, a two-pass internal cooling channel with engine-similar cross-sections was investigated numerically. The channel featured a trapezoidal inlet pass, a sharp 180° bend and a nearly rectangular outlet pass. Calculations were conducted for a configuration with smooth walls and walls equipped with 45° skewed ribs (P/e = 10, e/dh = 0.1) at a Reynolds number of Re = 50,000. The present study focused on the effect of rotation on fluid flow and heat transfer. The investigated rotation numbers were Ro = 0.0 and 0.10. The computations were performed by solving the Reynolds-averaged Navier-Stokes equations (RANS method) with the commercial Finite-Volume solver FLUENT using a low-Re k-ω-SST turbulence model. The numerical grids were block-structured hexahedral meshes generated with POINTWISE. Flow field measurements were independently performed at DLR using Particle Image Velocimetry. In the smooth channel rotation had a large impact on secondary flows. Especially, rotation induced vortices completely changed the flow field. Rotation also changed flow impingement on tip and outlet pass side wall. Heat transfer in the outlet pass was strongly altered by rotation. In contrast to the smooth channel, rotation showed less influence on heat transfer in the ribbed channel. This is due to a strong secondary flow field induced by the ribs. However, in the outlet pass Coriolis force markedly affected the rib induced secondary flow field. The influence of rotation on heat transfer was visible in particular in the bend region and in the second pass directly downstream of the bend.

Detached Eddy Simulation of Flow and Heat Transfer in a Stationary Internal Cooling Duct With Skewed Ribs

2005 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Detached Eddy Simulation ◽  
Square Duct ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Flow Features

Numerical predictions of a hydrodynamic and thermally developed turbulent flow for a unit period of a stationary duct using Detached Eddy Simulation (DES) and Unsteady Reynolds Averaged Navier-Stokes (URANS) are presented. The domain under consideration is a square duct with 45° ribs on the top and bottom walls arranged in a staggered fashion. Computations are carried out for a bulk Re of 47,000. The rib height to channel hydraulic diameter (e/Dh) is 0.1 and the rib pitch to rib height (P/e) is 10. DES is applied on two grids 80 × 80 × 80 and 128 × 80 × 80 and the initial results are compared with the experimental results and LES computations. Based on this the 128 × 80 × 80 grid is chosen for the comprehensive study. DES and URANS computations are carried out on the grid. The rib geometry introduces a strong secondary flow along the rib. The presence of the secondary flow introduces a spanwise variation in the heat transfer. DES predicts flow features and heat transfer distribution which is consistent with the experimental observations and LES computations. The average friction and the augmentation ratios predicted by DES also concur with the earlier observations.

scholarly journals Effect of Reynolds Number and Property Variation on Fluid Flow and Heat Transfer in the Entrance Region of a Turbine Blade Internal-Cooling Channel

2005 ◽  
Vol 2005 (1) ◽  
pp. 36-44 ◽  
Author(s):  
R. Ben-Mansour ◽  
L. Al-Hadhrami
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mass Flow Rate ◽  
Heat Transfer Rate ◽  
Turbine Blade ◽  
Flow Rate ◽  
Transfer Rate ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Flow And Heat Transfer

Internal cooling is one of the effective techniques to cool turbine blades from inside. This internal cooling is achieved by pumping a relatively cold fluid through the internal-cooling channels. These channels are fed through short channels placed at the root of the turbine blade, usually called entrance region channels. The entrance region at the root of the turbine blade usually has a different geometry than the internal-cooling channel of the blade. This study investigates numerically the fluid flow and heat transfer in one-pass smooth isothermally heated channel using the RNGk−εmodel. The effect of Reynolds number on the flow and heat transfer characteristics has been studied for two mass flow rate ratios (1/1and1/2) for the same cooling channel. The Reynolds number was varied between10 000and50 000. The study has shown that the cooling channel goes through hydrodynamic and thermal development which necessitates a detailed flow and heat transfer study to evaluate the pressure drop and heat transfer rates. For the case of unbalanced mass flow rate ratio, a maximum difference of8.9% in the heat transfer rate between the top and bottom surfaces occurs atRe=10 000while the total heat transfer rate from both surfaces is the same for the balanced mass flow rate case. The effect of temperature-dependent property variation showed a small change in the heat transfer rates when all properties were allowed to vary with temperature. However, individual effects can be significant such as the effect of density variation, which resulted in as much as9.6% reduction in the heat transfer rate.

3-D Internal Flow and Conjugate Calculations of a Convective Cooled Turbine Blade With Serpentine-Shaped and Ribbed Channels

1999 ◽  
Author(s):  
Dieter E. Bohn ◽  
Volker J. Becker ◽  
Karsten A. Kusterer ◽  
Yokiu Otsuki ◽  
Takao Sugimoto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Turbine Blade ◽  
Solid Body ◽  
Gas Turbines ◽  
Heat Transfer Analysis ◽  
Numerical Code ◽  
Cooling Channel ◽  
Flow And Heat Transfer ◽  
Body Regions

Modern cooling configurations for turbine blades include complex serpentine-shaped cooling channel geometries for internal-forced convective cooling. The channels are ribbed in order to enhance the convective beat transfer. The design of such cooling configurations is within the power of modem CFD-codes with combined heat transfer analysis in solid body regions. One approach is the conjugate fluid flow and heat transfer solver, CHT-Flow, developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It takes into account of the mutual influences of internal and external fluid flow and heat transfer. The strategy of the procedure is based on a multi-block-technique and a direct coupling module for fluid flow regions and solid body regions. The configuration under investigation in the present paper is based on a test design of a convective cooled turbine blade with serpentine-shaped cooling passages and cooling gas ejection at the blade tip and the trailing edge. The numerical investigations focus on secondary flow phenomena in the ducts and on the heat transfer analysis at the cooling channel walls. In the first part, the cooling channels are investigated with adiabatic smooth & ribbed walls. The calculations are carried out for the stationary and rotating configuration. Concerning the heat transfer analysis, the results of the ribbed configuration with a fixed thermal boundary condition at the walls in the stationary case are presented. Furthermore, in order to demonstrate the capability of the conjugate method to work without thermal boundary conditions, the cooling configuration is calculated including the external blade flow and the blade walls with internal and external heat transfer under typical operation conditions of gas turbines. The numerical code is used to determine the blade surface temperatures.

Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in Ribbed Coolant Passages of Different Aspect Ratios

2004 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Rotation Number ◽  
Large Scale ◽  
Density Ratio ◽  
Navier Stokes ◽  
Flow Structures ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Unsteady Rans

The flow and heat transfer in ribbed coolant passages of aspect ratios (AR) of 1:1, 4:1, and 1:4 are numerically studied through the solution of the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The URANS procedure can resolve large-scale bulk unsteadiness, and utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The computations are carried out for a fixed Reynolds number of 25000 and density ratio of 0.13 while the Rotation number has been varied between 0.12–0.50. The average duct heat transfer is the highest for the 4:1 AR case. For this case, the secondary flow structures consist of multiple roll cells that direct flow both to the trailing and leading surfaces. The 1:4 AR duct shows flow reversal along the leading surface at high rotation numbers with multiple rolls in the secondary flow structures near the leading wall. For this AR, the potential for conduction-limited heat transfer along the leading surface is identified. At high rotation number, both the 1:1 and 4:1 AR cases exhibit loss of axial periodicity over one inter-rib module. The friction factor reveals an increase with the rotation number for all aspect ratio ducts, and shows a sudden jump in its value at a critical rotation number because of either loss of spatial periodicity or the onset of backflow.

Effects of a flow mode transition on natural convection heat transfer in a heat tracing enclosure

2018 ◽  
Vol 233 (3) ◽  
pp. 489-499 ◽  
Author(s):  
CJ Ho ◽  
GN Sou ◽  
CM Lai
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Convection Heat Transfer ◽  
Flow Mode ◽  
Mode Transition ◽  
Flow And Heat Transfer ◽  
Lower Variation

This paper presents a numerical study of transient buoyancy-induced fluid flow and heat transfer between two horizontal, differentially heated pipelines inside a circular, air-filled enclosure. Numerical simulations based on the finite difference method were conducted to investigate the flow mode transition of the buoyant airflow and its effects on the heat transfer characteristics of the pipelines. The results indicate that the fluid flow complexity and the heat transfer of air between the pipelines are strongly affected by the Rayleigh number. When Ra = 6 × 105 and 1.2 × 106, both the flow field and the temperature distribution exhibit periodic variations with different patterns. The former ( Ra = 6 × 105) is a complete alteration of the flow direction from clockwise to counterclockwise, whereas the latter is a variation in the flow field strength that varies between strong and weak. The latter has a lower variation frequency than that of the former.

A Comparative Study of DES and URANS in a Two-Pass Internal Cooling Duct With Normal Ribs

2005 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Detached Eddy Simulation ◽  
Mean Flow ◽  
Streamline Curvature ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Developing Flow

The capabilities of the Detached Eddy Simulation (DES) and the Unsteady Reynolds Averaged Navier-Stokes (URANS) versions of the 1988 κ-ω model in predicting the turbulent flow field and the heat transfer in a two-pass internal cooling duct with normal ribs is presented. The flow is dominated by the separation and reattachment of shear layers; unsteady vorticity induced secondary flows and strong streamline curvature. The techniques are evaluated in predicting the developing flow at the entrance to the duct and downstream of the 180° bend, fully-developed regime in the first pass, and in the 180° bend. Results of mean flow quantities, secondary flows, friction and heat transfer are compared to experiments and Large-Eddy Simulations (LES). DES predicts a slower flow development than LES, while URANS predicts it much earlier than LES computations and experiments. However it is observed that as fully developed conditions are established, the capability of the base model in predicting the flow and heat transfer is enhanced by switching to the DES formulation. DES accurately predicts the flow and heat transfer both in the fully-developed region as well as the 180° bend of the duct. URANS fails to predict the secondary flows in the fully-developed region of the duct and is clearly inferior to DES in the 180° bend.

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