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.

Influence of Rib Turbulators on Pin-Fin Heat Transfer in the Trailing Region of Gas Turbine Vane: A Numerical Study

2006 ◽  
Author(s):  
N. Kulasekharan ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Flux Boundary Condition ◽  
Pin Fin ◽  
Pin Fins ◽  
Rib Turbulators

A numerical investigation is carried out for estimating the influence of rib turbulators on heat transfer and pressure drop of staggered non-uniform pin-fin arrays of different shapes, in a simulated cambered vane trailing region. Pin-fins of square, circular and the diamond shapes, each of two sizes (d) were chosen. The ratio of span-wise pitch to longitudinal pitch is 1.06 and that to the pin size are 4.25 and 3.03, for all pin shapes. A constant heat flux boundary condition is assumed over the coolant channel walls, rib surfaces and circumferential faces of the pin-fins. Reynolds number is varied (20,000<ReD<40,000) by changing the coolant outlet to inlet pressure ratio. Pin end-wall and pin surface averaged heat transfer coefficients and Nusselt numbers are estimated and detailed contours of heat transfer coefficient on both the pressure and suction surfaces are presented. Whilst there is an enhancement in heat transfer and pressure drop with ribs for all the pin shapes, diamond pins have shown the highest enhancement values for both ribbed and non-ribbed configuration.

Thermal performance enhancement in a wedge duct with in-line pin fins combined with vortex generators

2019 ◽  
Vol 29 (8) ◽  
pp. 2545-2565
Author(s):  
Safeer Hussain ◽  
Jian Liu ◽  
Lei Wang ◽  
Bengt Ake Sunden
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Vortex Generators ◽  
Content Type ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Enhancement

Purpose The purpose of this paper is to enhance the heat transfer and thermal performance in the trailing edge region of the vane with vortex generators (VGs). Design/methodology/approach This numerical study presents the enhancement of thermal performance in the trailing part of a gas turbine blade. In the trailing part, generally, pin fins are used either in staggered or in-line arrangements to enhance the heat transfer. In this study, based on the idea from heat exchangers, pin fins are combined with VGs. A pair of VGs is embedded in the boundary layer upstream of each pin fin in the first row of the pin fin array having an in-line configuration. The effects of the VG angle relative to the streamwise direction and streamwise distance between the pin fin and VGs are investigated at various Reynolds numbers. Findings The results indicated that the endwall heat transfer is enhanced with the addition of VGs and the heat transfer from the surfaces of the pin fins. The level of heat transfer enhancement compared to the case without VGs is more significant at high Reynolds number. The surfaces of the VGs also show a significant amount of heat transfer. Study of the angle of the attack suggested that a high angle of attack is more appropriate for pin fin cooling enhancement whereas an intermediate gap between the VGs and pin fins shows considerable improvement of thermal performance compared to the small and large gaps. The phenomenon of heat transfer augmentation with the VGs is demonstrated by the flow field. It shows that the enhancement of heat transfer is governed by the mixing of the flow as a result of the interaction of vortices generated by the VGs and pin fins. Originality/value VGs are used to disturb the thermal boundary layer. It shows that heat transfer is augmented as a result of the interaction of vortices associated with VGs and pin fins.

Experimental and Numerical Study on the Convective Heat Transfer and Pressure Loss in Rectangular Ducts With Inclined Pin-Fin on a Wavy Endwall

2012 ◽  
Author(s):  
K. Takeishi ◽  
Y. Oda ◽  
Y. Miyake ◽  
Y. Motoda
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pressure Loss ◽  
Numerical Study ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Pin Fin ◽  
Pin Fins

Local endwall heat transfer characteristics and overall pressure loss of normal and inclined pin fins arrayed in rectangular ducts with flat and wavy endwalls have been investigated to improve the cooling efficiency of jet engine combustor liners. The detailed time-mean local Nusselt number profiles were measured using a naphthalene sublimation method based on the heat/mass transfer analogy. Four kinds of angled pin fins (−45, 0, and +45 degrees with a flat endwall, and −45 degrees with a wavy endwall) were tested and compared with each other. As a result, the average heat transfer coefficient on the flat endwall of normal pin fins was higher than that of the angled pin fins. The average heat transfer coefficient of −45-degree inclined pin fins with a wavy endwall is the same or a little higher than the heat transfer coefficient of those with a flat endwall; however, the pressure loss of the −45-degree inclined pin fins with a wavy endwall is less than the pressure loss of those with a flat endwall. Corresponding numerical simulations using Large Eddy Simulation (LES) with the Mixed Time Scale (MTS) model have been also conducted at Red = 1000 for fully developed regions, and the results have shown good quantitative agreement with mass transfer experiments. It can be concluded that wavy endwalls can realize better heat transfer with less pressure loss as long as the aim consists in enhancing endwall heat transfer in inclined pin-fin channels.

Numerical Study on Flow and Heat Transfer Characteristics of Pin-Fins With Different Shapes

2019 ◽  
Author(s):  
Wei Jin ◽  
Ning Jia ◽  
Junmei Wu ◽  
Jiang Lei ◽  
Lin Liu
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Study ◽  
Heated Surface ◽  
Transfer Effect ◽  
Enhancement Effect ◽  
Trailing Edge ◽  
Pin Fin ◽  
Flow And Heat Transfer ◽  
Pin Fins

Abstract Equipping pin-fins in the blade trailing edge is an significant method for enhancing heat transfer. In order to obtain a geometry of pin-fins with good heat transfer effect and small friction factor, six pin-fins (circular, elliptic, oblong, teardrop, lancet and NACA) are selected. The flow and heat transfer features of the rectangular channel with the staggered pin-fins were numerically studied through FLUENT software. The channels with different pin-fins have the same relative spanwise pitch (S/D = 2.5) and streamwise pitch (X/D = 2.5), and the range of Reynolds number is 5×103 to 3×104. The applicability and accuracy of five turbulence models (Standard k-ε, Realizable k-ε, RNG k-ε, Standard k-ω and SST k-ω) are checked by comparing the numerically predicted results with the experimental from literature. It is found that the Realizable k-ε model is better at capturing the microstructure of flow field and has higher precision in predicting the averaged Nusselt number on the heated surface. For the six pin-fins, the leading edge is surrounded by a “U-shaped” strong heat exchange zone, but the vortex systems in the trailing edge are different from each other. Compared to the circular pin-fin, the oblong pin-fin has the best heat transfer enhancement effect, but the friction factor of channel is also larger. While the NACA pin-fin has the lowest friction factor, and the heat transfer effect is second only to the oblong. NACA pin-fin may be applied in blade trailing edge cooling by further optimizing the relative position of the pin-fins in the channel.

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.

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.

Numerical Study on Heat Transfer Characteristics in Rectangular Ducts With Pin-Fins

2011 ◽  
Author(s):  
Xinjun Wang ◽  
Xiaowei Bai ◽  
Jiangbo Wu ◽  
Rui Liu ◽  
Ding Zhu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Flow Direction ◽  
Three Dimensional ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Pin Fins

By using the CFX software, three-dimensional flow and heat transfer characteristics in rectangular cooling ducts with in-line and staggered array pin-fins of gas turbine blade trailing edge were numerically simulated. The effects of in-line and staggered arrays of pin-fins, flow Reynolds number as well as density of cylindrical pin-fins in flow direction on heat transfer characteristics were analyzed. Both in the cases of in-line and staggered arrays of pin-fins, the results show that the pin-fin surface averaged Nusselt number increases with the increasing of Reynolds number. In the case of the same Reynolds number, the mean Nusselt number of pin-fin surface decreased with the increasing of X/D (the ratio of streamwise pin-pitch to pin-fin diameter) value. The Nusselt number increases gradually before the first pin-fin row and then reached the fully developed value at fourth or fifth row. The pin-fin Nusselt number at flow direction is larger than that at back flow direction. Along the height direction of pin-fin, the Nusselt number in middle area is larger.

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.

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.

scholarly journals Numerical Study of Thermal-Hydraulic Performance of a New Spiral Z-Type PCHE for Supercritical CO2 Brayton Cycle

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4417
Author(s):  
Tingting Xu ◽  
Hongxia Zhao ◽  
Miao Wang ◽  
Jianhui Qi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Optimal Structure ◽  
Original Structure ◽  
Brayton Cycle ◽  
Compact Structure ◽  
Spiral Angle

Printed circuit heat exchangers (PCHEs) have the characteristics of high temperature and high pressure resistance, as well as compact structure, so they are widely used in the supercritical carbon dioxide (S-CO2) Brayton cycle. In order to fully study the heat transfer process of the Z-type PCHE, a numerical model of traditional Z-type PCHE was established and the accuracy of the model was verified. On this basis, a new type of spiral PCHE (S-ZPCHE) is proposed in this paper. The segmental design method was used to compare the pressure changes under 5 different spiral angles, and it was found that increasing the spiral angle θ of the spiral structure will reduce the pressure drop of the fluid. The effects of different spiral angles on the thermal-hydraulic performance of S-ZPCHE were compared. The results show that the pressure loss of fluid is greatly reduced, while the heat transfer performance is slightly reduced, and it was concluded that the spiral angle of 20° is optimal. The local fluid flow states of the original structure and the optimal structure were compared to analyze the reason for the pressure drop reduction effect of the optimal structure. Finally, the performance of the optimal structure was analyzed under variable working conditions. The results show that the effect of reducing pressure loss of the new S-ZPCHE is more obvious in the low Reynolds number region.

Sign in / Sign up

Export Citation Format

Share Document