Characteristics of Partial Length Circular Pin Fins as Heat Transfer Augmentors for Airfoil Internal Cooling Passages

1989 ◽  
Author(s):  
S. C. Arora ◽  
W. Abdel-Messeh
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
The Other ◽  
Internal Cooling ◽  
Partial Length ◽  
Smooth Channel ◽  
Pin Fins ◽  
Turbine Airfoils

Pin fins are commonly used as heat transfer augmentors for internal cooling of turbine airfoils. These pins may extend from one wall to the other or may be segmented to meet specific requirements of removing the airfoil’s varying heat load. Three configurations of the partial pins were tested in a 25:1 aspect ratio channel and the results are compared with those for the full pins. The array average heat transfer rate decreases linearly with increasing gap and is bounded by the value for full pins at one end and that for the smooth channel at the other. However, the local distribution of the Nusselt number and the average for each of the two walls depends on the configuration of the partial pins. The friction factor was lower for partial pins than for the full pins and also decreased with increasing gap. For the configuration with all partial pins on one wall, the friction factor was found to be the lowest with no change in the corresponding heat transfer rate from a wall with pins.

Characteristics of Partial Length Circular Pin Fins As Heat Transfer Augmentors for Airfoil Internal Cooling Passages

1990 ◽  
Vol 112 (3) ◽  
pp. 559-565 ◽  
Author(s):  
S. C. Arora ◽  
W. Abdel-Messeh
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
The Other ◽  
Internal Cooling ◽  
Partial Length ◽  
Smooth Channel ◽  
Pin Fins ◽  
Turbine Airfoils

Pin fins are commonly used as heat transfer augmentors for internal cooling of turbine airfoils. These pins may extend from one wall to the other or may be segmented to meet specific requirements of removing the airfoil’s varying heat load. Three configurations of the partial pins were tested in a channel with aspect ratio 25:1 and the results are compared with those for the full pins. The array average heat transfer rate decreases linearly with increasing gap and is bounded by the value for full pins at one end and that for the smooth channel at the other. However, the local distribution of the Nusselt number and the average for each of the two walls depends on the configuration of the partial pins. The friction factor was lower for partial pins than for the full pins and also decreased with increasing gap. For the configuration with all partial pins on one wall, the friction factor was found to be the lowest, with no change in the corresponding heat transfer rate from a wall with pins.

Thermal Performance Assessment of Turbulent Flow Through Dimpled Tubes

2010 ◽  
Author(s):  
Pornchai Nivesrangsan ◽  
Somsak Pethkool ◽  
Kwanchai Nanan ◽  
Monsak Pimsarn ◽  
Smith Eiamsa-ard
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Staggered Arrangement ◽  
Plain Tube ◽  
Pitch Ratio ◽  
Surface Patterns

This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/Di = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (A-A) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined.

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.

scholarly journals Numerical Investigation of Heat Transfer and Friction Factor Characteristics in a Circular Tube Fitted with V-Cut Twisted Tape Inserts

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sami D. Salman ◽  
Abdul Amir H. Kadhum ◽  
Mohd S. Takriff ◽  
Abu Bakar Mohamad
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Investigation ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Twisted Tape ◽  
Maximum Heat ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Twist Ratio

Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y=2.93) and different cut depths (w=0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y=2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratioy=2.93and cut depthw=0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.

Inaccuracy of Heat Transfer Characteristics for Pin Fins Considering the Influence of Heat Radiation

2011 ◽  
Vol 199-200 ◽  
pp. 1513-1517
Author(s):  
Fu Jen Wang ◽  
Jung Chieh Chang ◽  
Kuo Chien Lin ◽  
King Leung Wong
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Radiation Effect ◽  
Heat Radiation ◽  
Convection Coefficient ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Pin Fins

Pin fins are widely applied in heat exchanger industry. The heat transfer characteristics of pin fins can be found in many textbooks and handbooks related to heat transfer or heat exchanger. However, most heat transfer experts recognized from their own experiences that the heat radiation effect equation contained the fourth order exponential of temperature and the emissivity of oxidized metal are higher, the inaccuracy of heat transfer rate might be higher while ignoring the effect of heat radiation. In this study, numerical simulation using computational fluid dynamics (CFD) code was conducted to verify the heat transfer characteristics of pin fins. It is found that the error of heat transfer rate generated by ignoring heat radiation will be as high as 45 % while heat convection coefficient is 10 (Wm-2K-1 ) associated with the emissivity of fin surface is 1.0. It also revealed the heat radiation effect cannot be neglected for pin fins, especially for the application under high emissivity and low heat convection coefficient conditions.

scholarly journals Heat Transfer Augmentation Technologies for Internal Cooling of Turbine Components of Gas Turbine Engines

2013 ◽  
Vol 2013 ◽  
pp. 1-32 ◽  
Author(s):  
Phil Ligrani
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Thermal Performance ◽  
Density Ratio ◽  
Extensive Literature ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Heat Transfer Augmentation ◽  
Pin Fins ◽  
Rib Turbulators

To provide an overview of the current state of the art of heat transfer augmentation schemes employed for internal cooling of turbine blades and components, results from an extensive literature review are presented with data from internal cooling channels, both with and without rotation. According to this survey, a very small number of existing investigations consider the use of combination devices for internal passage heat transfer augmentation. Examples are rib turbulators, pin fins, and dimples together, a combination of pin fins and dimples, and rib turbulators and pin fins in combination. The results of such studies are compared with data obtained prior to 2003 without rotation influences. Those data are comprised of heat transfer augmentation results for internal cooling channels, with rib turbulators, pin fins, dimpled surfaces, surfaces with protrusions, swirl chambers, or surface roughness. This comparison reveals that all of the new data, obtained since 2003, collect within the distribution of globally averaged data obtained from investigations conducted prior to 2003 (without rotation influences). The same conclusion in regard to data distributions is also reached in regard to globally averaged thermal performance parameters as they vary with friction factor ratio. These comparisons, made on the basis of such judgment criteria, lead to the conclusion that improvements in our ability to provide better spatially-averaged thermal protection have been minimal since 2003. When rotation is present, existing investigations provide little evidence of overall increases or decreases in overall thermal performance characteristics with rotation, at any value of rotation number, buoyancy parameter, density ratio, or Reynolds number. Comparisons between existing rotating channel experimental data and the results obtained prior to 2003, without rotation influences, also show that rotation has little effect on overall spatially-averaged thermal performance as a function of friction factor.

Establishing a Methodology for Resolving Convective Heat Transfer From Complex Geometries

2008 ◽  
Author(s):  
J. Ostanek ◽  
K. Thole ◽  
J. Prausa ◽  
A. Van Suetendael
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Model Approximation ◽  
Lumped Model ◽  
Smooth Channel ◽  
Loop Channel ◽  
Turbine Airfoils

Current turbine airfoils must operate at extreme temperatures, which are continuously driven higher by the demand for high output engines. Internal cooling plays a key role in the longevity of gas turbine airfoils. Ribbed channels are commonly used to increase heat transfer by generating turbulence and to provide a greater convective surface area. Because of the increasing complexity in airfoil design and manufacturing, a methodology is needed to accurately measure the convection coefficient of a rib with a complex shape. Previous studies that have measured the contribution to convective heat transfer from the rib itself have used simple rib geometries. This paper presents a new methodology to measure convective heat transfer coefficients on complex ribbed surfaces. The new method was applied to a relatively simple shape so that comparisons could be made with a commonly accepted method for heat transfer measurements. A numerical analysis was performed to reduce experimental uncertainty and to verify the lumped model approximation used in the new methodology. Experimental measurements were taken in a closed-loop channel using fully rounded, discontinuous, skewed ribs oriented 45° to the flow. The channel aspect ratio was 1.7:1 and the ratio of rib height to hydraulic diameter was 0.075. Heat transfer augmentation levels relative to a smooth channel were measured to be between 4.7 and 3 for Reynolds numbers ranging from 10,000 to 100,000.

scholarly journals STATIC THERMAL ANALYSIS OF FINS MODELS USING ANSYS

2020 ◽  
Author(s):  
Rajat Kumar ◽  
Devendra Singh ◽  
Ajay Kumar Sharma
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Dissipation ◽  
Thermal Stresses ◽  
Temperature Variations ◽  
Finite Element Software ◽  
Pin Fins ◽  
Over The Top

The Engine chamber is one of the essential engine components, that is subjected to over the top temperature differences and thermal stresses. Fins are set on the surface of the cylinder to improve the quantity of heat exchange by convection. When fuel is burned in an engine, heat is produced. Additional heat is also generated by friction between the moving parts. In air-cooled I.C engine, extended surfaces called fins are provided at the periphery of engine cylinder to increase heat transfer rate. That is why the analysis of fin is important to increase the heat transfer rate. The main of aim of this work is to study various researches done in past to improve heat transfer rate of cooling fins by changing cylinder fin geometry and material. In the present work, Experiments have been performed to discover the temperature variations inside the fins made in four kind geometries (plate Fins, Circular Pin fins, plate fins with holes, and draft Pin fins) and consistent state heat exchange examination has been studied utilizing a finite element software ANSYS to test and approve results. The temperature variations at various areas of fins models are evaluated by FEM and compared models of fins performance by heat flux and temperature variations obtained by experimentally in Analysis. The principle implemented in this project is to expand the heat dissipation rate by utilizing the wind flow. The main aim of the study is to enhance the thermal properties by shifting geometry, material, and design of fins

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