H225 Flow and Heat Transfer Characteristics of Low Reynolds Number Viscoelastic Fluid Flow in a Serpentine Channel : 4th Report: Measurement of Local Heat Transfer Coefficient in the Developing and Developed Regions

2014 ◽  
Vol 2014 (0) ◽  
pp. _H225-1_-_H225-2_
Author(s):  
Ryuichi KIMURA ◽  
Wataru NAGASAKA ◽  
Kazuya TATSUMI ◽  
Kazuyoshi NAKABE
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Characteristics ◽  
Serpentine Channel ◽  
Flow And Heat Transfer

Detailed Experimental Characterization of Heat Transfer Coefficient Over the Internal Cooling Passages of an Additive Manufactured Turbine Airfoil

2016 ◽  
Author(s):  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Jae Y. Um ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Scale Model ◽  
Internal Cooling ◽  
Trailing Edge

This report describes the detailed experimental study to characterize the local heat transfer coefficient distribution over the internal cooling passages of a simplified generic airfoil. The airfoil is manufactured through additive manufacturing based on actual geometry and dimensions (1X scale model) of row one airfoil, applicable in large gas turbine system. At the mainbody section, the serpentine channel consists of three passages without any surface features or vortex generators. Both the leading edge and trailing edge sections are subjected to direct impingement. The trailing edge section is divided into three chambers, separated by two rows of blockages. This study employs the well-documented transient liquid crystal technique, where the local heat transfer coefficient on both pressure and suction sides is deduced. The experiments were performed at varying Reynolds number, ranging from approximately 31,000–63,000. The heat transfer distribution on the pressure side and suction side is largely comparable in the first and third pass, except for the second pass. Highest heat transfer occurs at the trailing edge region, which is ultimately dominated by impingement due to the presence of three rows of blockages. A cursory numerical calculation is performed using commercially available software, ANSYS CFX to obtain detailed flow field distribution within the airfoil, which explains the heat transfer behavior at each passage. The flow parameter results revealed that the pressure ratio is strongly proportional with increasing Reynolds number.

Numerical Simulations of Flow Fields and Heat Transfer Characteristics in Tenon Joint Gap Between Turbine Blade and Disk Under Rotating Conditions

2017 ◽  
Author(s):  
Da-wei Chen ◽  
Hui-ren Zhu ◽  
Yang Xu ◽  
Xiao-meng Jia ◽  
Cong Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Flow And Heat Transfer ◽  
Joint Gap ◽  
The Right

Turbine blades and the disks are connected by tenons. There is a pair of jagged assembly clearance between each tenon and corresponding mortise. In practical engineering applications, flow and heat transfer characteristics in assembly clearance used to be simplified. In order to obtain more accurate temperature fields of the turbine blades and disks, detailed study of the flow and heat transfer mechanism in tenon joint gap is necessary. In this paper, two typical assembly clearances under the stationary and rotating conditions were investigated numerically, including double S-shaped and double Crescent-shaped. The inlet Reynolds numbers range from 5,500 to 50,000 and the Rotation numbers range from 0 to 0.005. The results show that the fluids in the two branches of the double S-shaped channel have different flow characteristics under rotating conditions. A vortex is formed at the corner of the left branch and the vortex scale can be influenced by Re and Ro. The large vortex decreases the local heat transfer coefficient. In the right branch, the three-dimensional flow from the flat wall to the concave wall increases the local heat transfer coefficient of different regions. For the double Crescent-shaped channel, the region with higher velocity is offset to the right of the channel which leads to higher local heat transfer coefficient under rotating conditions. The simulation results have great significance to the heat transfer analysis of turbine blades and disks.

Thermal Transport From a Rotating Disk During Partially Confined Liquid Jet Impingement

2007 ◽  
Author(s):  
Jorge Lallave ◽  
Muhammad M. Rahman
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Liquid Jet ◽  
Interface Temperature

This paper presents a numerical study that characterizes the conjugate heat transfer results of a semi–confined liquid jet impingement on a uniformly heated spinning solid disk of finite thickness and radius. The model covers the entire fluid region including the impinging jet on a flat circular disk and flow spreading out downstream under the confined insulated wall that ultimately gets exposed to a free surface boundary condition. The solution is made under steady state and laminar conditions. The model examines how the heat transfer is affected by adding a secondary rotational flow under semi-confined jet impingement. The study considered various standard materials, namely aluminum, copper, silver, Constantan and silicon; covering a range of flow Reynolds number (220–900), under a broad rotational rate range from 0 to 750 rpm, or Ekman number (7.08×10−5 – ∞), nozzle to target spacing (β = 0.25 – 1.0), disk thicknesses to nozzle diameter ratio (b/dn = 0.25 – 1.67), Prandtl number (1.29 – 124.44) using ammonia (NH3), water (H2O), flouroinert (FC-77) and oil (MIL-7808) as working fluids and solid to fluid thermal conductivity ratio (36.91 – 2222). High thermal conductivity plate materials maintained more uniform and lower interface temperature distributions. Higher Reynolds number increased local heat transfer coefficient reducing the interface temperature difference over the entire wall. Rotational rate increases local heat transfer coefficient under most conditions. These findings are important for the design improvement and control of semi-confined liquid jet impingement under a secondary rotation induced motion.

Local Heat Transfer in a Rotating Square Channel With Jet Impingement

1999 ◽  
Vol 121 (4) ◽  
pp. 811-818 ◽  
Author(s):  
S.-S. Hsieh ◽  
J.-T. Huang ◽  
C.-F. Liu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient

The influence of rotation and jet mass flow rate on the local heat transfer coefficient for a single confined impinging round jet with a fixed jet-to-wall spacing of H/d = 5 was studied for the jet Reynolds number from 6500 to 26,000 and the rotational Reynolds number from 0 to 112,000. The local heat transfer coefficient along the surface is measured and the effect of the rotation on the stagnation (peak) point, local and average Nusselt number, is presented and discussed. Furthermore, a correlation was developed for the average Nusselt number in terms of the parameters of Rej and ReΩ. In general, the combined jet impingement and rotation effect are shown to affect the heat transfer response. Rotation decreases the average Nusselt number values from 15 to 25 percent in outward and inward radial flow, respectively. Finally, comparisons of the present data with existing results for multijets with rotation were also made.

Numerical Prediction of 45° Angled Ribs Effects on U-shaped Channels Heat Transfer and Flow under Multi Conditions

2020 ◽  
Vol 37 (1) ◽  
pp. 41-59 ◽  
Author(s):  
Longfei Wang ◽  
Songtao Wang ◽  
Xun Zhou ◽  
Fengbo Wen ◽  
Zhongqi Wang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Narrow Channel ◽  
Aspect Ratios ◽  
Cooling Air Flow

AbstractRibs effects on the heat transfer performance and cooling air flow characteristics in various aspect ratios (AR) U-shaped channels under different working conditions are numerically investigated. The ribs angle and channel orientation are 45° and 90°, respectively, and the aspect ratios are 1:2, 1:1, 2:1. The inlet Reynolds number changes from 1e4 to 4e4 and rotational speeds include 0, 550 rpm, 1,100 rpm. Local heat transfer coefficient, endwall surface heat transfer coefficient ratio and augmentation factor are the three primary criteria to measure channel heat transfer. Ribs increase the heat transfer area and improve heat transfer coefficient of ribbed surfaces significantly, especially in the 1st pass, while the endwall surface contributes more to channel heat transfer because of the larger area and relatively smaller heat transfer coefficient. The wide channel (AR =2:1) owns the better augmentation factor than the narrow channel (AR =1:2) and ribs heat transfer weight increases with an increase of the inlet Reynolds number. Rotating slightly reduces the ribs heat transfer weight in channel and the trailing surface in 1st pass is the main influence object of rotating.

Modeling of Convective Cooling of a Rotating Disk by Partially Confined Liquid Jet Impingement

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
Jorge C. Lallave ◽  
Muhammad M. Rahman
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Liquid Jet

This paper presents the results of the numerical simulation of conjugate heat transfer during a semiconfined liquid jet impingement on a uniformly heated spinning solid disk of finite thickness and radius. This study considered various disk materials, namely, aluminum, copper, silver, Constantan, and silicon; covering a range of Reynolds number (220–900), Ekman number (7.08×10−5–∞), nozzle-to-target spacing (β=0.25–1.0), disk thicknesses to nozzle diameter ratio (b∕dn=0.25–1.67), and Prandtl number (1.29–124.44) using ammonia (NH3), water (H2O), flouroinert (FC-77), and oil (MIL-7808) as working fluids. The solid to fluid thermal conductivity ratio was 36.91–2222. A higher thermal conductivity plate material maintained a more uniform interface temperature distribution. A higher Reynolds number increased the local heat transfer coefficient. The rotational rate also increased the local heat transfer coefficient under most conditions.

Flow Structure and Heat Transfer During Free Liquid Jet Impingement on a Hemispherical Plate

2006 ◽  
Author(s):  
Muhammad M. Rahman ◽  
Cesar F. Hernandez ◽  
Jorge C. Lallave
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Liquid Jet ◽  
Fluid Interface ◽  
Solid Plate

The flow structure and convective heat transfer behavior of a free liquid jet impinging on a hemispherical solid plate of finite thickness have been examined using a numerical analysis. The simulation model included the entire fluid region (impinging jet and flow spreading out over the convex surface) and solid plate as a conjugate problem. Solution was done for both isothermal and constant heat flux boundary conditions at the inner surface of the hemispherical plate. Computations were done for jet Reynolds number (ReJ) ranging from 500 to 2000 and the dimensionless nozzle to target spacing ratio (β) from 0.75 to 3. Results are presented for local heat transfer coefficient and the local Nusselt number using the following working fluids: water (H2O), flouroinert (FC-77), and oil (MIL-7808) and for various solid materials namely aluminum, Constantan, copper, silicon, and silver. It was observed that plate materials with higher thermal conductivity maintained a more uniform temperature distribution at the solid-fluid interface. A higher Reynolds number increased the Nusselt number and local heat transfer coefficient distributions over the entire solid-fluid interface.

A Novel Microelectronics Cooling Technique Using a Pair of Unsteady Confined Impinging Air Jets

2003 ◽  
Author(s):  
Jorge L. Rosales ◽  
Victor A. Chiriac
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Heat Sources ◽  
Air Jets ◽  
Target Wall

The unsteady laminar flow and heat transfer characteristics for a pair of confined impinging air jets centered in a channel were studied numerically. The time-averaged heat transfer coefficient for a pair of heat sources centered in the channel and aligned with the jets was determined as well as the oscillating jet frequency for the unsteady cases. The present study continues the authors’ previous investigation, which emphasized how single confined jets will remain steady at Reynolds numbers that make side-by-side jets highly unsteady. The nature of this unsteadiness depends on the proximity of the jet inlets, the channel dimensions and the jet Reynolds number. The jet unsteadiness causes the stagnation point locations to sweep back and forth over the impingement region, and the jets “wash” a larger surface area on the target wall. The results indicate that the dual jets become unsteady between a Reynolds number of 200 and 300. Also, in the range of Reynolds numbers studied, a fixed stagnation “bubble” was formed on the target wall between the two jets, which reduced the heat transfer removal from that region, leading in fact to a quasi-independence of the local heat transfer on flow conditions. The stagnant region contains slow moving warm air that forces the cool impinging air jets to flow to the sides of this target wall area. The oscillating frequency of the flow increases with Reynolds number for the unsteady cases. Also, the time-averaged heat transfer coefficient on the heat sources rises as the Reynolds number increases for the steady cases but there is a slight decrease when it transitions to unsteady flow, indicating again that the stagnation “bubble” occurring between the two heat sources affects the local heat transfer.

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