Numerical Simulation of Flow and Heat Transfer in Rotating Cooling Passage With Turning Vane in Hub Region

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Hung-Chieh Chu ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Complex Flow ◽  
Flow And Heat Transfer ◽  
Cooling Passage ◽  
Turn Region

Numerical simulation of three-dimensional turbulent flow and heat transfer was performed in a multipass rectangular (AR = 2:1) rotating cooling channel with and without turning vane in the hub region under various flow conditions, with two different Reynolds numbers of 10,000 and 25,000, two different channel orientations of 45-deg and 90-deg, and the rotation number varies from 0 to 0.2. This study shows that the addition of the turning vane in the hub turn region does not cause much impact to the flow before the hub. However, it significantly alters the flow reattachment and vortex distribution in the hub turn region and after the hub turn portion. The local heat transfer is deeply influenced by this complex flow field and this turning vane effect lasts from the hub turn region to the portion after it.

Numerical Simulation of Flow and Heat Transfer in Rotating Cooling Passage With Turning Vane in Hub Region

2013 ◽  
Author(s):  
Hung-Chieh Chu ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Complex Flow ◽  
Local Flow ◽  
The Third ◽  
Flow And Heat Transfer ◽  
Cooling Passage

Numerical simulation of three-dimensional turbulent flow and heat transfer was performed in a multi-pass rectangular (AR = 2:1) rotating cooling channel with and without turning vane in the hub region under various flow conditions, with two different Reynolds numbers of 10000 and 25000, two different channel orientations of 45-deg and 90-deg., and the rotation number varies from 0 to 0.2. The present study provides detailed explanation on the dramatic flow change due to the turning vane. The numerical results show that the addition of vane in hub portion does not cause much impact to the flow before the turn. However, it greatly affects flow behaviors and heat transfer characteristics in the turning region and the third passage after the hub turn. Compared to the cases without turning vane, the vane clearly changes local flow pattern, divides the main flow into two separate streams, and alters the flow reattachment location and vortex distribution. The local heat transfer is influenced by this complex flow field and its effects last from the turn portion to the third passage.

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

Numerical Analysis of Laminar Flow and Heat Transfer for an Abrupt Circular Contraction

2002 ◽  
Author(s):  
S. Piva ◽  
D. Sambinello ◽  
M. W. Collins
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Clear Understanding ◽  
Practical Case ◽  
Accurate Data ◽  
Flow And Heat Transfer ◽  
Contraction Ratio ◽  
Property Changes

Detailed predictions have been made of laminar thermo-fluid entry effects for the important practical case of an abrupt circular contraction. The Computational Fluid Dynamics code CFDS-FLOW3D (now CFX) was used, and special care was taken to achieve accurate data, by attention to issues of algorithm choice and grid fineness. Assuming constant properties, detailed local heat transfer predictions have been obtained, for a range of Prandtl and Reynolds numbers and contraction ratio β. The near-entry heat transfer is consistent with the flow behaviour, and gives a clear understanding of the process involved. Qualitatively the results are comparable with experimental and predictive data available in the literature, where however substantial effects due to property changes with temperature were evidenced. This study confirms the presence of flow separation and recirculation found and inferred by other authors, and investigates the phenomena in considerably more detail.

Computation of Flow and Heat Transfer of a Blade Internal Cooling Passage With Truncated V-Shaped Ribs on Opposite Walls

2012 ◽  
Author(s):  
Shian Li ◽  
Gongnan Xie ◽  
Weihong Zhang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Turbine Engine ◽  
Flow And Heat Transfer ◽  
Cooling Passage ◽  
Internal Cooling Passage

The inlet temperature of gas turbine engine is continuously increased to achieve higher thermal efficiency and power output. To prevent from the temperature exceeding the melting point of the blade material, ribs are commonly used in the mid-section of internal blade to augment the heat transfer from blade wall to the coolant. In this study, turbulent flow and heat transfer of a rectangular cooling passage with continuous or truncated 45-deg V-shaped ribs on opposite walls have been investigated numerically. The inlet Reynolds numbers are ranging from 12,000 to 60,000 and the low-Re k-ε model is selected for the turbulent computations. The complex three-dimensional fluid flow in the internal coolant passages and the corresponding heat transfer over the side-walls and rib-walls are presented and the thermal performances of the ribbed passages are compared as well. It is shown that the passage with truncated V-shaped ribs on opposite walls is very effective in improving the heat transfer performance with a low pressure loss, and thus could be suggested to be applied to gas turbine blade internal cooling.

scholarly journals Influence of the Gap Size Between Side Walls and Ribs on the Heat Transfer in a Stationary and Rotating Straight Rib-roughened Duct

2000 ◽  
Vol 6 (4) ◽  
pp. 253-263 ◽  
Author(s):  
R. Kiml ◽  
S. Mochizuki ◽  
A. Murata
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Flow Direction ◽  
Three Dimensional ◽  
Side Wall ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Wall Region ◽  
Side Walls ◽  
Cooling Passage

The objective of this study is to investigate a heat transfer phenomenon in a straight ribroughened duct which represents a cooling passage of a modern gas turbine blade. Experiments were performed for ribs mounted perpendicularly to the main flow direction on two opposite sides of the duct for the following cases: (1) with no gaps, (2) with gaps=0.33hand (3) with gaps=1hbetween the side walls and ribs (wherehis the rib height). The heat transfer results revealed significant differences among these three cases, showing that the existence of gaps increases the heat transfer. Particularly, the local heat transfer on the wall between the consecutive ribs is higher in the near-side wall region than in the central region. To shed some light on this phenomenon, flow visualization was conducted using the particle tracer method. The flow visualization results revealed the effect of gaps on the three-dimensional flow structure between the ribs. It was concluded that this structure caused the heat transfer enhancement in the near-side wall region.

Heat Transfer Measurements on a Cooled Flat Plate Simulating Actual Size Turbine Hardware

1999 ◽  
Author(s):  
J. Lepicovsky ◽  
T. J. Bencic
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mach Number ◽  
Flat Plate ◽  
Boundary Layers ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Rates ◽  
Cooling Passage

Application of thin-film thermocouples and temperature sensitive paint to surface temperature and heat transfer rate measurement on a flat plate with internal cooling is described in this paper. The test arrangement was designed to model flow and heat transfer conditions in terms of gas (external) and coolant (internal) Reynolds numbers that are typical for cooled turbine components. The test article is geometrically simple; however, from the heat transfer point of view it represents a fairly complex case. For both flows, internal and external, the hydrodynamic boundary layers start well ahead of the thermal boundary layers. The thermally active surface is preceded by an adiabatic starting length. Also, the heat transfer occurs under nonisothermal wall conditions and nonuniform heat flux conditions. The heat transfer experiments were carried out for a range of Mach number and Reynolds number on the gas side from 0.17 to 0.53 and from 135 000 to 580 000, respectively. On the coolant side, the corresponding ranges were from 0.3 to 0.52 for the flow Mach number, and from 20 000 to 65 000 for the Reynolds number. Measured bulk heat transfer rates demonstrated expected trends as functions of external (gas) and internal (coolant) Reynolds numbers. Local heat transfer rates measured along the mid-span line behaved as expected in relation to the internal (coolant) Reynolds number. However, they seem to be insensitive to changes in the external (gas) Reynolds number — at least for the particular test arrangement. Local heat transfer rates, however, strongly depend on the location with respect to the width of the cooling passage. These results were not expected; they may be caused by three dimensional nature of heat convection and conduction in this test arrangement.

Numerical Simulation of Coupling Heat Transfer in Sealed Airborne Electronic Equipments

2013 ◽  
Vol 275-277 ◽  
pp. 642-648
Author(s):  
Hong Xia Gao ◽  
Zhan Xiao ◽  
Yong Qi Xie
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Natural Convection ◽  
Electromagnetic Interference ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Maximum Error ◽  
Local Heat ◽  
Empirical Method ◽  
Electronic Products

For shielding radio frequency and electromagnetic interference, the sealed case is usually used for airborne electronic equipment. As electronic products become faster and incorporate greater functionality, their thermal characters must be well analyzed and designed. Three-dimensional thermal numerical simulations from inside to outside of the sealed case were performed to get a clear sight of the coupling heat transfer in conduction, natural convection, and radiation. Temperature field, fluid flow field, and local heat transfer coefficient layout outside the wall were got, which were compared with the outcomes of the empirical method. The results of numerical simulation showed that in sealed case conduction was the dominant way, and natural convection had the comparative ratio with radiation, both of them were less than 25%. The maximum error of no radiation including could get to 43.2%.

Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct

1967 ◽  
Vol 89 (2) ◽  
pp. 163-167 ◽  
Author(s):  
E. G. Filetti ◽  
W. M. Kays
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Duct Flow ◽  
Double Step ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Flow Cross

Experimental data are presented for local heat transfer rates near the entrance to a flat duct in which there is an abrupt symmetrical enlargement in flow cross section. Two enlargement area ratios are considered, and Reynolds numbers, based on duct hydraulic diameter, varied from 70,000 to 205,000. It is found that such a flow is characterized by a long stall on one side and a short stall on the other. Maximum heat transfer occurs in both cases at the point of reattachment, followed by a decay toward the values for fully developed duct flow. Empirical equations are given for the Nusselt number at the reattachment point, correlated as functions of duct Reynolds number and enlargement ratio.

Local Heat Transfer Measurements in Turbulent Flow Around a 180-deg Pipe Bend

1987 ◽  
Vol 109 (1) ◽  
pp. 43-48 ◽  
Author(s):  
J. W. Baughn ◽  
H. Iacovides ◽  
D. C. Jackson ◽  
B. E. Launder
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Secondary Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Pipe Bend ◽  
Streamline Curvature

The paper reports extensive connective heat transfer data for turbulent flow of air around a U-bend with a ratio of bend radius:pipe diameter of 3.375:1. Experiments cover Reynolds numbers from 2 × 104 to 1.1 × 105. Measurements of local heat transfer coefficient are made at six stations and at five circumferential positions at each station. At Re = 6 × 104 a detailed mapping of the temperature field within the air is made at the same stations. The experiment duplicates the flow configuration for which Azzola and Humphrey [3] have recently reported laser-Doppler measurements of the mean and turbulent velocity field. The measurements show a strong augmentation of heat transfer coefficient on the outside of the bend and relatively low levels on the inside associated with the combined effects of secondary flow and the amplification/suppression of turbulent mixing by streamline curvature. The peak level of Nu occurs halfway around the bend at which position the heat transfer coefficient on the outside is about three times that on the inside. Another feature of interest is that a strongly nonuniform Nu persists six diameters downstream of the bend even though secondary flow and streamline curvature are negligible there. At the entry to the bend there are signs of partial laminarization on the inside of the bend, an effect that is more pronounced at lower Reynolds numbers.

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