An Experimental and Numerical Study of Flow and Heat Transfer in Channels With Pin Fin-Dimple Combined Arrays of Different Configurations

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Yu Rao ◽  
Chaoyi Wan ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Experimental Conditions ◽  
Number Range ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Reynolds Number Range

An experimental and numerical study was conducted to investigate the flow and heat transfer characteristics in channels with pin fin-dimple combined arrays of different configurations, where dimples are located transversely or both transversely and streamwisely between the pin fins. The flow structure, friction factor, and heat transfer characteristics of the pin fin-dimple channels of different configurations have been obtained and compared with each other for the Reynolds number range of 8200–50,500. The experimental study showed that, compared to the pin fin channel, depending on the configurations of the pin fin-dimple combined arrays the pin fin-dimple channel can have distinctively further improved convective heat transfer performance by 8.0%–20.0%, whereas lower or slightly higher friction factors over the studied Reynolds number range. Furthermore, three-dimensional and steady-state conjugate computations have been carried out for similar experimental conditions. The numerical computations showed detailed characteristics of the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the pressure loss and heat transfer characteristics in the pin fin-dimple channels of different configurations.

A Numerical Study of the Flow and Heat Transfer in the Pin Fin-Dimple Channels With Various Dimple Depths

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Yu Rao ◽  
Yamin Xu ◽  
Chaoyi Wan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Number Range ◽  
Flow Friction ◽  
Pin Fin ◽  
Flow And Heat Transfer

A numerical study was conducted to investigate the effects of dimple depth on the flow and heat transfer characteristics in a pin fin-dimple channel, where dimples are located spanwisely between the pin fins. The study aimed at promoting the understanding of the underlying convective heat transfer mechanisms in the pin fin-dimple channels and improving the cooling design for the gas turbine components. The flow structure, friction factor, and heat transfer performance of the pin fin-dimple channels with various dimple depths have been obtained and compared with each other for the Reynolds number range of 8200–80,800. The study showed that, compared to the pin fin channel, the pin fin-dimple channels have further improved convective heat transfer performance, and the pin fin-dimple channel with deeper dimples shows relatively higher Nusselt number values. The study still showed a dimple depth-dependent flow friction performance for the pin fin-dimple channels compared to the pin fin channel, and the pin fin-dimple channel with shallower dimples shows relatively lower friction factors over the studied Reynolds number range. Furthermore, the computations showed the detailed characteristics in the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the heat transfer enhancement and flow friction reduction phenomenon in the pin fin-dimple channels.

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

2010 ◽  
Author(s):  
Tarek M. Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.

Numerical Investigation on the Flow and Heat Transfer Characteristics of the Superheated Steam in the Wedge Duct With Pin-Fins

2013 ◽  
Author(s):  
Gaoliang Liao ◽  
Xinjun Wang ◽  
Xiaowei Bai ◽  
Ding Zhu ◽  
Jinling Yao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Three Dimensional ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Steam Superheat

By using the CFX software, the three-dimensional flow and heat transfer characteristics in the cooling duct with pin-fin in the blade trailing edge were numerically simulated. The effects of pin-fin arrangements, Reynolds number, steam superheat degrees, streamwise pin density and convergence angle of the wedge duct on the flow and heat transfer characteristics were analysed. The results show that the Nusselt number on the endwall and pin-fin surfaces as well as the pin-fin row averaged Nusselt number increase with the increasing of Reynolds number, while it decreased with the with the increasing of X/D. The pressure drop increases with the increasing of Reynolds number while decreases with the increasing of X/D in the wedge duct. The degree of superheat has little effect on the pressure loss in the wedge duct. A comprehensive analysis and comparison show that the highest thermal performance is reached in the wedge duct when the value of X/D is 1.5.

scholarly journals Flow and heat transfer characteristics around an elliptic cylinder placed in front of a curved plate

2014 ◽  
Vol 18 (2) ◽  
pp. 465-478
Author(s):  
Mahmoud Mostafa ◽  
Radwan Kamal ◽  
Mohamed Gobran
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Angle Of Attack ◽  
Elliptic Cylinder ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Reynolds Number Range

An experimental investigation has been conducted to clarify heat transfer characteristics and flow behaviors around an elliptic cylinder. Also, flow visualization was carried out to clarify the flow patterns around the cylinder. The elliptic cylinder examined has an axis ratio of 1:2.17, was placed in the focus of parabolic plate. The test fluid is air and the Reynolds number based on the major axis length, c, ranged from 5 x 103 to 3 x 104. The angle of attack (?) was changed from 0? to 90? at 15? interval. It is found that the pressure distribution, form drag, location of separation point, and heat transfer coefficient depend strongly upon the angle of attack. Over the Reynolds number range examined, the mean heat transfer coefficient is at its highest at ? = 60? - 90?. The values of heat transfer coefficient in the case of free cylinder are higher than those for cylinder/plate combination at all angles of attack and Reynolds number range examined.

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.

Effect of the Inlet Geometry on the Flow and Heat Transfer Characteristics of Three-Dimensional Wall Jets

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Sangamesh C. Godi ◽  
Arvind Pattamatta ◽  
C. Balaji
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Three Dimensional ◽  
Heat Transfer Characteristics ◽  
Wall Jets ◽  
Number Range ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Circular Jets

Abstract In this work, fluid flow and heat transfer characteristics of three-dimensional (3D) wall jets exiting from a circular and square opening are presented based on experimental investigations. Two hydraulic diameters, namely, 2.5 and 7.5 mm and a Reynolds number range of 5000–20,000 have been considered. Mean velocity and turbulence intensity distribution in the walljet are quantified using a hot wire anemometry. Measurements are done both along the streamwise and spanwise directions. Transient infrared thermography is used for mapping the temperatures over the surface, and the heat transfer coefficients are estimated using a semi-infinite approximation methodology. Results show that, for circular jets, the effect of the jet diameter on the local and the spanwise-averaged Nusselt number is most pronounced near the jet exit. Further, it is also observed that circular jets have an edge over square jets. A correlation with a high correlation coefficient of 0.95 has been developed for spanwise average Nusselt number as a function of the Reynolds number and the dimensionless streamwise distance.

Flow and Heat Transfer Characteristics in Latticework Cooling Channels With Dimple Vortex Generators

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Yu Rao ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Numerical Study ◽  
Vortex Generators ◽  
Vortical Flow ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Cooling Channels ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

A comparative experimental and numerical study has been conducted on the flow and heat transfer characteristics in a latticework cooling channel with U-shaped subchannels combined with dimple vortex generators over the Reynolds number range of 7700–36,985. The average Nusselt number and friction factor of the latticework channel have been obtained. The comparisons between the experimental and numerical data have shown that the numerical computation model can reasonably well predict the heat transfer and pressure loss in the latticework cooling channels. Additional numerical computations were further performed to investigate the effects of subchannel configurations on the flow and heat transfer in the latticework channel, and three different subchannel configurations were studied, which are the dimpled U subchannel, U subchannel, and rectangular subchannel. The experimental data of the heat transfer and pressure loss of the latticework channel with dimpled U subchannels have also been compared with those of the ribbed channels and pin fin channel from the literature. The present study indicated that the superior heat transfer enhancement capability of the latticework cooling is mainly due to the remarkably increased heat transfer area, turning effects producing strong vortical flow in the subchannels, and the interactions between the flow in the crossing subchannels, as well as the interactions between the flow and the crossing ribs on the opposite side.

Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

2021 ◽  
pp. 095440622110272
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Litan Kumar Saha ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

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