Heat Transfer in Trailing Edge Wedge-Shaped Pin-Fin Channels With Slot Ejection Under High Rotation Numbers

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Yao-Hsien Liu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
High Heat ◽  
Copper Plate ◽  
Trailing Edge ◽  
Pin Fin ◽  
High Heat Transfer ◽  
Rotation Numbers ◽  
Smooth Channel ◽  
Pin Fins

The heat transfer characteristics of a rotating pin-fin roughened wedge-shaped channel have been studied. The model incorporates ejection through slots machined on the narrower end of the wedge, simulating a rotor blade trailing edge. The copper plate regional average method is used to determine the heat transfer coefficient; pressure taps have been used to estimate the flow discharged through each slot. Tests have been conducted at high rotation (≈1) and buoyancy (≈2) numbers, in a pressurized rotating rig. Reynolds numbers investigated range from 10,000 to 40,000 and inlet rotation numbers range from 0 to 0.8. Pin-fins studied are made of copper. Results show high heat transfer in the proximity of the slot. A significant enhancement in heat transfer due to the pin-fins, compared with a smooth channel, is observed. Results also show a strong rotation effect, increasing significantly the heat transfer on the trailing surface and reducing the heat transfer on the leading surface.

Heat Transfer in Trailing Edge Wedge-Shaped Pin-Fin Channels With Slot Ejection Under High Rotation Numbers

2010 ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Yao-Hsien Liu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Significant Enhancement ◽  
Trailing Edge ◽  
Pin Fin ◽  
High Heat Transfer ◽  
Smooth Channel ◽  
Pin Fins ◽  
The Heat Transfer Coefficient

The heat transfer characteristics of a rotating pin-fin roughened wedge shaped channel have been studied. The model incorporates ejection through slots machined on the narrower end of the wedge, simulating a rotor blade trailing edge. The copperplate regional average method is used to determine the heat transfer coefficient; pressure taps have been used to estimate the flow discharged through each slot. Tests have been conducted at high rotation (≈ 1 ) and buoyancy (≈ 2) numbers, in a pressurized rotating rig. Reynolds Numbers investigated range from 10,000 to 40,000 and rotational speeds range from 0–400rpm. Pin-fins studied are made of copper as well as non-conducting garolite. Results show high heat transfer coefficients in the proximity of the slot. A significant enhancement in heat transfer due to the pin-fins, compared with a smooth channel is observed. Even the non-conducting pin-fins, indicative of heat transfer on the end-wall show a significant enhancement in the heat transfer coefficient. Results also show a strong rotation effect, increasing significantly the heat transfer coefficient on the trailing surface — and reducing the heat transfer on the leading surface.

Heat Transfer Characteristics of a Flow Passage With Long Pin Fins and Improving Heat Transfer Coefficient by Adding Turbulence Promoters on a Endwall

2001 ◽  
Author(s):  
K. Takeishi ◽  
T. Nakae ◽  
K. Watanabe ◽  
M. Hirayama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
High Heat ◽  
Atmospheric Conditions ◽  
Pin Fin ◽  
High Heat Transfer ◽  
Turbine Vanes ◽  
Pin Fins

Pin fins are normally used for cooling the trailing edge region of a turbine, where their aspect ratio (height H/diameter D) is characteristically low. In small turbine vanes and blades, however, pin fins may also be located in the middle region of the airfoil. In this case, the aspect ratio can be quite large, usually obtaining values greater than 4. Heat transfer tests, which are conducted under atmospheric conditions for the cooling design of turbine vanes and blades, may overestimate the heat transfer coefficient of the pin-finned flow channel for such long pin fins. The fin efficiency of a long pin fin is almost unity in a low heat transfer situation as it would be encountered under atmospheric conditions, but can be considerably lower under high heat transfer conditions and for pin fins made of low thermal conductivity material. A series of tests with corresponding heat transfer models has been conducted in order to clarify the heat transfer characteristics of the long pin-finned flow channel. It is assumed that heat transfer coefficients can be predicted by the linear combination of two heat transfer equations, which were separately developed for the pin fin surface and for tubes in crossflow. To confirm the suggested combined equations, experiments have been carried out, in which the aspect ratio and the thermal conductivity of the pin were the test parameters. To maintain a high heat transfer coefficient for a long pin fin under high-pressure conditions, the heat transfer was augmented by adding a turbulence promoter on the pin-finned endwall surface. A corresponding equation that describes this situation has been developed. The predicted and measured values showed good agreement. In this paper, a comprehensive study on the heat transfer of a long pin-fin array will be presented.

Effect of Pin-fins On Jet Impingement Heat Transfer Over a Rotating Disk

2021 ◽  
Author(s):  
Pratik S. Bhansali ◽  
Kishore Ranganath Ramakrishnan ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
High Heat ◽  
Maximum Enhancement ◽  
Pin Fin ◽  
Smooth Disk ◽  
Pin Fins

Abstract Many engineering applications consist of rotating components which experience high heat load. For instance, applications like the gas turbine engine consist of rotating disks and the study of heat transfer over such rotating surfaces is of particular interest. In the case of gas turbines, the disk also needs to be protected from the ingress of hot turbine gases caused by the low pressure region created due to the radially outward pumping of fluid close to the rotating surface. Present experimental study investigates the effects of introducing pin-fins on heat transfer over surface of a rotating gas turbine disk. Experiments were conducted at rotational Reynolds numbers (ReR) of 5487 - 12803 and jet Reynolds numbers (Re) of 5000 - 18000, nozzle to target spacing (z/d = 2 - 6), impingement eccentricities (e = 0 -0.67), angles of impingement (0°-20°), and the pin fin height (Hf = 3.05mm - 19.05mm). Steady state temperature measurements were taken using thermocouples embedded in the disk, and area average Nusselt number (Nu) was calculated. The results have been compared with those for a smooth aluminum disk. Nu was significantly enhanced by the presence of pin-fins. The enhancement was higher for lower Re and the maximum enhancement was found to be 3.9 times that of a smooth disk for Re = 5000. Qualitative visualization of flow field has been performed for smooth and the pin-fin case using the commercial simulation package Ansys Fluent to further understand the flow features that result in the enhancement.

Heat Transfer in a Rib Turbulated Pin Fin Array for Trailing Edge Cooling

2021 ◽  
pp. 1-42
Author(s):  
Marcel Otto ◽  
Jayanta Kapat ◽  
Mark Ricklick ◽  
Shantanu Mhetras
Keyword(s):  
Heat Transfer ◽  
Positive Impact ◽  
High Heat ◽  
Thermochromic Liquid Crystal ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
High Heat Transfer ◽  
Pin Fins ◽  
Rib Turbulators ◽  
Pin Fin Array

Abstract Ribs were added into a pin fin array for a uniquely new cooling concept enabled through additive manufacturing. Both heat transfer mechanisms are highly non-linear; thus, cannot be superimposed. Heat transfer measurements are obtained using the thermochromic liquid crystal technique in a trapezoidal duct with pin fins and rib turbulators. Three pin blockage ratios and four rib heights at Reynolds numbers between 40,000 and 106,000 were tested. The Nusselt number augmentation is generally higher at the longer base of the trapezoidal duct. The same high heat transfer trend is seen at the columns closer to the longer base of the trapezoidal duct than on the shorter base. Through the length of the duct, the flow shifts from the nose region to the larger opening on the opposite wall. Also, it is observed that increasing the blockage ratio as well as increasing the rib height, has a positive impact on heat transfer as ribs act as additional extended surfaces and alter the near-wall flow field. The heat transfer augmentation of pins and ribs is found to not be equal to the sum of both. The observed heat transfer augmentation of the combined cases exceeded over the rib and pin only cases by up to 100%, but the weighted friction factor also doubled. The combination of ribs and pins is an excellent concept to achieve more uniform cooling over an array at higher levels when pressure drop is not of concern.

Effect of Corrugated Orifice and Pin-Fin on Multiple Array Impingement Cooling With Low Nozzle to Target Distance

2014 ◽  
Author(s):  
Li Yang ◽  
Weihong Li ◽  
Zhongran Chi ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Conjugate Heat Transfer ◽  
High Heat ◽  
Inlet Temperature ◽  
Impingement Cooling ◽  
Pin Fin ◽  
High Heat Transfer ◽  
Pin Fins ◽  
Heat Transfer Simulation

Impingement cooling is widely used in turbine vanes and combustors. With the increase of turbine inlet temperature, high heat transfer coefficient and low pressure drop are required for cooling structures. A series of new impingement configurations combined with corrugated orifice and pin-fins were developed in the present work. Both transient liquid crystal (TLC) and pressure measurement were applied on the impingement cooling structures. A 3D numerical method was also used for conjugate heat transfer simulation. Corrugated orifice helps decrease the pressure drop by decreasing the speed of cross flow. Experimental data show that, corrugated orifice is helpful in reducing pin-fin induced pressure drop but contributes little to heat transfer. Pin-fins increases both the heat transfer and pressure drop lightly. Conjugate heat transfer simulation shows that pin-fins significantly reduce the metal temperature by conduction. Structures with pin-fins can make a good use of the large surface area of corrugated orifices.

Effects of Non-Uniform Streamwise Spacing in Low Aspect Ratio Pin Fin Arrays

2013 ◽  
Author(s):  
Jason K. Ostanek ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
High Heat ◽  
Pin Fin ◽  
Uniform Spacing ◽  
High Heat Transfer ◽  
Uniform Array ◽  
High Reynolds ◽  
Turbine Airfoils ◽  
Pin Fin Arrays

Pin fin arrays are commonly used to cool the trailing edge of gas turbine airfoils. While the majority of pin fin research focuses on uniformly-spaced arrays, the goal of the present work was to determine if non-uniform spacing in the streamwise direction could be utilized to maintain high heat transfer while simultaneously extending the array footprint. The uniqueness of the work lies in the basis for selecting the non-uniform spacing pattern. The non-uniform arrangement was chosen to exploit previously published row-by-row heat transfer development where the initial rows showed little variation with streamwise spacing. As such, a non-uniform array was considered where the initial rows had spacing of 3.46 diameters and the inner rows gradually decreased to a final spacing of 1.73 diameters. Three seven-row arrays were considered having constant streamwise spacing of 2.16, 2.60, and 3.03 pin fin diameters. All configurations had constant spanwise spacing of two diameters and constant pin height of one diameter. Three Reynolds numbers of 3.0e3, 1.0e4, and 2.0e4 were considered based on pin fin diameter and minimum area velocity. At high Reynolds numbers, heat transfer and pressure drop measurements were in agreement for the nonuniform array and for a closely spaced array having 2.16 diameter streamwise spacing. While array performance was similar, the non-uniform array covered 16.8% more streamwise distance than the closely spaced array. At low Reynolds numbers, however, the non-uniform array was outperformed by the closely spaced array.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

scholarly journals Effects of Channel Outlet Configuration and Dimple/Protrusion Arrangement on the Blade Trailing Edge Cooling Performance

2019 ◽  
Vol 9 (14) ◽  
pp. 2900
Author(s):  
Qi Jing ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
High Heat ◽  
Wake Flow ◽  
Internal Cooling ◽  
Trailing Edge ◽  
Cooling Channels ◽  
High Heat Transfer ◽  
Channel Outlet ◽  
Staggered Arrangement

The trailing edge regions of high-temperature gas turbine blades are subjected to extremely high thermal loads and are affected by the external wake flow during operation, thus creating great challenges in internal cooling design. With the development of cooling technology, the dimple and protrusion have attracted wide attention for its excellent performance in heat transfer enhancement and flow resistance reduction. Based on the typical internal cooling structure of the turbine blade trailing edge, trapezoidal cooling channels with lateral extraction slots are modeled in this paper. Five channel outlet configurations, i.e., no second passage (OC1), radially inward flow second passage (OC2), radially outward flow second passage (OC3), top region outflow (OC4), both sides extractions (OC5), and three dimple/protrusion arrangements (all dimple, all protrusion, dimple–protrusion staggered arrangement) are considered. Numerical investigations are carried out, within the Re range of 10,000–100,000, to analyze the flow structures, heat transfer distributions, average heat transfer and friction characteristics and overall thermal performances in detail. The results show that the OC4 and OC5 cases have high heat transfer levels in general, while the heat transfer deterioration occurs in the OC1, OC2, and OC3 cases. For different dimple/protrusion arrangements, the protrusion case produces the best overall thermal performance. In conclusion, for the design of trailing edge cooling structures with lateral slots, the outlet configurations of top region outflow and both sides extractions, and the all protrusion arrangement, are recommended.

Effect of Rotation on Heat Transfer in Narrow Rectangular Cooling Channels (AR = 8:1 and 4:1) With Pin-Fins

2003 ◽  
Author(s):  
Lesley M. Wright ◽  
Eungsuk Lee ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Pin Fin ◽  
Aspect Ratios ◽  
Rectangular Channels ◽  
Smooth Channel ◽  
Pin Fins

The effect of rotation on smooth narrow rectangular channels and narrow rectangular channels with pin-fins is investigated in this study. Pin-fins are commonly used in the narrow sections within the trailing edge of the turbine blade; the pin-fins act as turbulators to enhance internal cooling while providing structural support in this narrow section of the blade. The rectangular channel is oriented at 150° with respect to the plane of rotation, and the focus of the study involves narrow channels with aspect ratios of 4:1 and 8:1. The enhancement due to both conducting (copper) pin-fins and non-conducting (plexi-glass) pins is investigated. Due to the varying aspect ratio of the channel, the height-to-diameter ratio (hp/Dp) of the pins varies from two, for an aspect ratio of 4:1, to unity, for an aspect ratio of 8:1. A staggered array of pins with uniform streamwise and spanwise spacing (xp/Dp = sp/Dp = 2.0) is studied. With this array, 42 pin-fins are used, giving a projected surface density of 3.5 pins/in2 (0.543 pins/cm2), for the leading or trailing surfaces. The range of flow parameters include Reynolds number (ReDh = 5000–20000), rotation number (Ro = 0.0–0.302), and inlet coolant-to-wall density ratio (Δρ/ρ = 0.12). Heat transfer in a stationary pin-fin channel can be enhanced up to 3.8 times that of a smooth channel. Rotation enhances the heat transferred from the pin-fin channels 1.5 times that of the stationary pin-fin channels. Overall, rotation enhances the heat transfer from all surfaces in both the smooth and pin-fin channels. Finally, as the rotation number increases, spanwise variation increases in all channels.

Heat Transfer Measurements in Rotating Blade–Shape Serpentine Coolant Passage With Ribbed Walls at High Reynolds Numbers

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Akhilesh Rallabandi ◽  
Jiang Lei ◽  
Je-Chin Han ◽  
Salam Azad ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Copper Plate ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Significant Deterioration ◽  
Turbine Cooling ◽  
Experimental Heat ◽  
Rotation Numbers ◽  
High Reynolds

Flow in the internal three-pass serpentine rib turbulated passages of an advanced high pressure rotor blade is simulated on a 1:1 scale in the laboratory. Tests to measure the effect of rotation on the Nusselt number are conducted at rotation numbers up to 0.4 and Reynolds numbers from 75,000 to 165,000. To achieve this similitude, pressurized Freon R134a vapor is utilized as the working fluid. Experimental heat transfer coefficient measurements are made using the copper-plate regional average method. Regional heat transfer coefficients are correlated with rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Strikingly, a significant deterioration in heat transfer is noticed in the “hub” region—between the radially inward second pass and the radially outward third pass. This heat transfer reduction is critical for turbine cooling designs.

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