Flow Field Around Dimpled Pin-Fins in a Staggered Array

2011 ◽  
Author(s):  
R. K. Nagar ◽  
J. P. Meyer ◽  
Md. MahbubAlam ◽  
G. Spedding
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Turbine Blades ◽  
Circular Cross Section ◽  
Enhanced Heat Transfer ◽  
Enhance Heat Transfer ◽  
Transfer Rates ◽  
Pin Fin ◽  
Low Aspect Ratio ◽  
Pin Fins

Pin fins are low aspect ratio rods of circular cross section that are used to enhance heat transfer inside turbine blades. Although modifying the basic circular geometry with numerous shallow depressions (dimples) has been linked with enhanced heat transfer rates, the fluid mechanical mechanisms have remained speculative. Here we investigate numerically the effects of dimples onthe mean and turbulence velocities that lead to increased heat transfer. It has been found that dimples result in an increased turbulence intensity which may possess a greater potential to extract and transport more heat from the pin-fin.

scholarly journals Heat Transfer From Low Aspect Ratio Pin Fins

2007 ◽  
Author(s):  
Michael E. Lyall ◽  
Alan A. Thrift ◽  
Atul Kohli ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Channel Height ◽  
Internal Cooling ◽  
Number Range ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Low Aspect Ratio ◽  
Pin Fins

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 to 30,000. Both pressure drop and spatially-resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.

Effects of Pin Shape and Array Orientation on Heat Transfer and Pressure Loss in Pin Fin Arrays

1984 ◽  
Vol 106 (1) ◽  
pp. 252-257 ◽  
Author(s):  
D. E. Metzger ◽  
C. S. Fan ◽  
S. W. Haley
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Pressure Loss ◽  
Flow Direction ◽  
Circular Cross Section ◽  
Cycle Performance ◽  
Mean Flow ◽  
Pin Fin ◽  
The Mean ◽  
Cooling Air

Modern high-performance gas turbine engines operate at high turbine inlet temperatures and require internal convection cooling of many of the components exposed to the hot gas flow. Cooling air is supplied from the engine compressor at a cost to cycle performance and a design goal is to provide necessary cooling with the minimum required cooling air flow. In conjunction with this objective, two families of pin fin array geometries which have potential for improving airfoil internal cooling performance were studied experimentally. One family utilizes pins of a circular cross section with various orientations of the array with respect to the mean flow direction. The second family utilizes pins with an oblong cross section with various pin orientations with respect to the mean flow direction. Both heat transfer and pressure loss characteristics are presented. The results indicate that the use of circular pins with array orientation between staggered and inline can in some cases increase heat transfer while decreasing pressure loss. The use of elongated pins increases heat transfer, but at a high cost of increased pressure loss. In conjunction with the present measurements, previously published results were reexamined in order to estimate the magnitude of heat transfer coefficients on the pin surfaces relative to those of the endwall surfaces. The estimate indicates that the pin surface coefficients are approximately double the endwall values.

scholarly journals Heat Transfer From Low Aspect Ratio Pin Fins

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Michael E. Lyall ◽  
Alan A. Thrift ◽  
Karen A. Thole ◽  
Atul Kohli
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Channel Height ◽  
Internal Cooling ◽  
Number Range ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Low Aspect Ratio ◽  
Pin Fins

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 and 30,000. Both pressure drop and spatially resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.

Numerical Evaluation of Pin Fin Inclination by Conjugate Heat Transfer Simulation With URANS

2015 ◽  
Author(s):  
Takashi Yamane
Keyword(s):  
Heat Transfer ◽  
Thermal Conduction ◽  
Conjugate Heat Transfer ◽  
Turbine Blades ◽  
Flow Region ◽  
Cooling Performance ◽  
Pin Fin ◽  
Blade Cooling ◽  
Pin Fins ◽  
Heat Transfer Simulation

Short pin fins are often used as one of the blade cooling technologies inside the trailing edge of turbine blades. In our previous study we focused on the effects of pin inclination for overall cooling performance especially including heat conduction between the pins and endwall by both experiments and the conjugate heat transfer simulations, then the forwardly inclined pin-fins are found to effectively enhance the cooling, but we also found that the steady conjugate heat transfer simulation underestimates the cooling performance of the straight pin-fins due to highly unsteady flow structure. In this study the URANS is coupled with the steady thermal conduction by using the time smoothing method in the flow region, thus the underestimate of the heat transfer for the straight pin-fins was significantly improved.

Enhanced Heat Transfer, Missing Pin, and Optimization for Cylindrical Pin Fin Arrays

1993 ◽  
Vol 115 (3) ◽  
pp. 576-583 ◽  
Author(s):  
B. A. Jubran ◽  
M. A. Hamdan ◽  
R. M. Abdualh
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Enhanced Heat Transfer ◽  
Pin Fin ◽  
Line Array ◽  
Pin Fins ◽  
Pin Fin Arrays

This paper reports an experimental investigation on the effects of interfin spacing, shroud clearance, and missing pin on the heat transfer from cylindrical pin fins arranged in staggered and in-line arrays. The interfin spacing in the span wise direction was so small that the pins were almost touching each other. It was found that the optimum interfin spacing in both spanwise and streamwise directions is 2.5 D regardless of both type of array and shroud clearance used. The effect of missing pin for various interfin spacing arrays was found to be negligible for the in-line array but more significant for the staggered arrays.

Numerical Study on Heat Transfer and Fluid Flow in Pin Fin-Dimple Channels With Fillet on Dimple Edge

2014 ◽  
Author(s):  
Muralikrishnan Gopalakrishnan Meena ◽  
Abhijith Anandakrishnan ◽  
Madhu Anandarajan Kavumcheril
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Turbine Blades ◽  
Constant Heat Flux ◽  
Original Structure ◽  
Frictional Loss ◽  
Modified Model ◽  
Pin Fin ◽  
Pin Fins ◽  
Work Done

Pin fins and dimples are used for enhancing heat transfer from surfaces and here we take into account their use in cooling the trailing edge of gas turbine blades. The main problem is the increase in pressure drop with increase in dimple depths. This is a vital factor for the total work done by the turbine. The models for which study has been conducted are the ones with dimple depths of 1mm, 2mm and 3mm. Also, as a modification, fillets are added to the edges of the dimples with 3mm depth. Turbulent flow with Re of about 55,000 is employed through the surface, which is heated with constant heat flux of 50,000 W/m2. The results showed that the modified model reduces the frictional loss to a large extent without creating much disturbance to the heat transfer capability of the original structure. The modified model gave the lowest amount of friction factor at the same time providing reasonable amount of heat transfer compared to the other three models.

Augmented Heat Transfer of Internal Blade Tip Wall With Pin-Fins

2009 ◽  
Author(s):  
G. N. Xie ◽  
B. Sunde´n ◽  
L. Wang ◽  
E. Utriainen
Keyword(s):  
Heat Transfer ◽  
Computational Models ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Inlet Temperature ◽  
Gas Flows ◽  
Pin Fin ◽  
Pin Fins ◽  
Blade Tip

The heat transferred to the turbine blade is substantially increased as the turbine inlet temperature is increased. Cooling methods are therefore much needed for the turbine blades to ensure a long durability and safe operation. The blade tip region is exposed to the hot gas flows. A common way to cool the tip is to use serpentine passages with 180-deg turn under the blade tip cap taking advantage of the three-dimensional turning effect and impingement. Improving internal convective cooling is therefore required to increase the blade tip life. In this paper, augmented heat transfer of a blade tip has been investigated numerically. The computational models consist of a two-pass channel with 180-deg turn and an array of pin-fins mounted on the tip-cap, and a smooth two-pass channel. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible and stationary. The detailed 3D fluid flow and heat transfer over the tip surfaces are presented. The overall performance of the two models is evaluated. It is found that the pin-fins make the counter-rotating vortices towards pin-fin surfaces, resulting in continuous turbulent mixing near the pin-finned tip. Due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of as much as 1.84 higher than that of a smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 35%. It is suggested that the pin-fins could be used to enhance blade tip heat transfer and cooling.

Numerical Predictions of Thermal and Hydraulic Performances of Heat Sinks With Enhanced Heat Transfer Capability

2011 ◽  
Author(s):  
Feng Zhou ◽  
Nicholas Hansen ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Section ◽  
Heat Sink ◽  
Heat Sinks ◽  
Pin Fin ◽  
Numerical Predictions ◽  
Pin Fins ◽  
New Type ◽  
Cross Section Profile

The plate-pin fin heat sink (PPFHS) is composed of a plate fin heat sink (PFHS) and some pin fins planted between the flow channels. In this paper, a numerical investigation was performed to compare the thermal and hydraulic performances of the PPFHSs and PFHS. PPFHSs with five forms of pin cross-section profiles (square, circular, elliptic, NACA 0050, and dropform) were numerically simulated. The influence of pin fin cross-section profile on the flow and heat transfer characteristics was presented by means of Nusselt number and pressure drop. It is found that the Nu number of a PPFHS is at least 35% higher than that of a PFHS used to construct the PPFHS at the same Reynolds number. Planting circular and square pins into the flow channel of heat sinks enhances the heat transfer at the expense of high pressure loss. Using the streamline shaped pins, not only the pressure drop of the compound heat sinks could be decreased considerably, the heat transfer enhancement also makes a step forward. The present numerical simulation provides original information of the influence of different pin-fin cross-section profiles on the thermal and hydraulic performance of the new type compound heat sink, which is helpful in the design of heat sinks.

Heat Transfer on Convective Surfaces With Pin-Fins Mounted in Inclined Angles

2007 ◽  
Author(s):  
M. K. Chyu ◽  
E. O. Oluyede ◽  
H.-K. Moon
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Casting Process ◽  
Local Heat ◽  
Test Model ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Pin Fins ◽  
Inclined Angle

Casting of pin fins at the trailing edge of the turbine blades often presents some difficulties due to tight dimensional tolerances, leaving the pin fins inclined after the casting process. This study is to experimentally examine the effects of such an imperfect manufacturing phenomena on the heat transfer and friction characteristics over pin-fin arrays with different pin inclinations. The test model is a staggered short (H/D = 1) pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed local heat transfer coefficients on both array endwalls and pin elements are determined using the transient liquid crystal technique, as the inclined angle θ varies from 40° to 90° and the Reynolds number ranges from 7.0 × 103 and 1.3 × 104. The measured data suggest that an increase in pin inclined angle relative to its normal orientation (90-degree) significantly reduces the level of heat transfer enhancement from the array. Such a reduction amounts to nearly 50% for the 40-degree case. The accompanied friction loss also decreases.

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