Numerical solution for fully developed flow in heated curved tubes

1982 ◽  
Vol 123 ◽  
pp. 503-522 ◽  
Author(s):  
J. Prusa ◽  
L. S. Yao
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Secondary Flow ◽  
Heat Transfer Rate ◽  
Centrifugal Force ◽  
Transfer Rate ◽  
Axial Temperature Gradient ◽  
Curved Tube ◽  
Axial Temperature ◽  
Axial Pressure Gradient

Fully developed laminar flow for a horizontal heated curved tube is studied numerically. The tube is heated so as to maintain a constant axial temperature gradient. A physical model is introduced that accounts for the combined effects of both buoyancy and centrifugal force. Results, for a Prandtl number of one, are presented for a moderate range of Dean numbers and the product of the Reynolds and Rayleigh numbers. Detailed predictions of the flow resistance, the average heat-transfer rate and the secondary-flow streamlines are given. Also presented are results on the position of the local maxima of shear stress and heat-transfer rate. The numerical results reveal that the mass-flow rate is drastically reduced owing to the secondary flow for a given axial pressure gradient. Consequently, the total heat- transfer rate decreases for a more-curved tube as well as for a larger axial temperature gradient. A flow-regime map is provided to indicate the three basic regimes where (i) centrifugal force dominates, (ii) both buoyancy and centrifugal forces are important, and (iii) buoyancy force dominates.

The Effect of Axisymmetric Profile on Turbine Blade Platform Heat Transfer Distribution

2013 ◽  
Author(s):  
Luzeng Zhang ◽  
Dong H. Lee ◽  
Juan Yin ◽  
Hee Koo Moon
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Heat Transfer Rate ◽  
Turbine Blade ◽  
Transfer Rate ◽  
Heat Load ◽  
Secondary Flows ◽  
Upstream Region ◽  
Aerodynamic Loss ◽  
Flat Profile

Flow field near the turbine blade platform is very complex due to the secondary flow motions such as horseshoe vortices, passage vortices and endwall cross flows. It is therefore extremely difficult to predict the platform heat transfer distribution. As the secondary flows are largely affected by platform profile/shape, a number of investigators have studied different platform profiles to minimize aerodynamic loss and heat load. Understanding of the platform heat transfer has become especially critical in recent years, because of firing temperature increase and low NOx combustion requirement, as it is directly related to turbine durability. Three different axisymmetric platform profiles were designed and experimentally studied: flat profile, dolphin nose profile and shark nose profile. All of them were based on the existing engine hardware designs. The measurements were conducted in a high-speed linear cascade, which consisted of five blades and six flow passages. The test platforms were made of FR4 material and painted with Thermo-chromic Liquid Crystal (TLC). The test article was kept in the plenum located under the cascade at the pre-test condition. At the start of each test, the test blade/article was inserted into the cascade rapidly and then two CCD cameras recorded the color changes of the TLC on the platform surface. Engine representative Reynolds numbers were studied from 300,000 to 600,000 and the corresponding inlet Mach numbers were ranged from 0.12 to 0.24. The upstream section of the flat profile platform showed a typical flat plate heat transfer pattern with boundary layer development. The shark-nose and dolphin-nose platforms resulted in lower heat transfer coefficients on the upstream region compared to that for the flat profile, and the peak values moved slightly downstream from the leading edge due to possibly different secondary flow patterns. The heat transfer rate increased with increased Reynolds number for all three platform shapes, while the flat profile showed a higher increase rate. Zone averaged heat transfer distributions in addition to local values were also presented to show the effect of platform profile. In general, the flat profile platform resulted in a higher overall heat transfer rate than that for the other two profile platforms, which suggested that a good design of contoured profile platform could reduce the heat load and aerodynamic loss in gas turbine blade.

scholarly journals Numerical Simulation of Steady and Unsteady Flow and Entropy Generation by Nanofluid Within a Sinusoidal Channel

2021 ◽  
Vol 89 (2) ◽  
pp. 25-42
Author(s):  
Ehsan Kianpour ◽  
Nor Azwadi Che Sidik ◽  
Seyyed Muhammad Hossein Razavi Dehkordi ◽  
Siti Nurul Akmal Yusof
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Temperature Gradient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Control Volume ◽  
Human Life ◽  
Middle Part ◽  
Uniform Heat Flux ◽  
Parallel Plates

Heat transfer has always been one of the most important aspects of human life. So far, many sources have been reported on methods of increasing the heat transfer rate. Many of these methods focus on changes in equipment structure. These techniques can hardly cope with the growing demand for heat transfer and compression in equipment. Recent advances in nanoparticle production can be seen as a breakthrough in methods of increasing heat transfer. The purpose of this study is to numerically investigate the flow field and heat transfer of water-aluminium oxide nanofluid in a wavy channel. The channel consists of two parallel plates and is divided into three parts in the longitudinal direction. The beginning and end parts of the channel are insulated and the middle part is sinusoidal and receives a uniform heat flux. The nanofluid enters the channel at a uniform speed and temperature and exits it in an expanded manner. For numerical analyses, the finite difference method based on control volume and simple algorithm is used. In this research, Reynold’s effect was analysed. The results showed that by increasing the Reynolds number, the speed, temperature gradient and heat transfer rate was increased and the thickness of the thermal boundary layer was decreased. With increasing Reynolds number, the amount of heat transfer from the wall to the fluid and also the production of entropy increases. In the unsteady state, with increasing time and flow rate, the amount of heat transfer and total entropy and temperature gradient increase to reach the steady state.

Ferro-nanofluid squeeze film lubrication with heat transfer

2021 ◽  
pp. 135065012110276
Author(s):  
Manimegalai Kavarthalai ◽  
Vimala Ponnuswamy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Contact Time ◽  
Transfer Rate ◽  
Fluid Layer ◽  
Darcy Law ◽  
Squeeze Film ◽  
Mean Temperature ◽  
Special Cases ◽  
The Impact

A theoretical study of a squeezing ferro-nanofluid flow including thermal effects is carried out with application to bearings and articular cartilages. A representational geometry of the thin layer of a ferro-nanofluid squeezed between a flat rigid disk and a thin porous bed is considered. The flow behaviours and heat transfer in the fluid and porous regions are investigated. The mathematical problem is formulated based on the Neuringer–Rosensweig model for ferro-nanofluids in the fluid region including an external magnetic field, Darcy law for the porous region and Beavers–Joseph slip condition at the fluid–porous interface. The expressions for velocity, fluid film thickness, contact time, fluid flux, streamlines, pathlines, mean temperature and heat transfer rate in the fluid and porous regions are obtained by using a perturbation method. An asymptotic solution for the fluid layer thickness is also presented. The problem is also solved by a numerical method and the results by asymptotic analysis, perturbation and numerical methods are obtained assuming a constant force squeezing state and are compared. It is shown that the results obtained by all the methods agree well with each other. The effects of various parameters such as Darcy number, Beavers–Joseph constant and magnetization parameter on the flow behaviours, contact time, mean temperature and heat transfer rate are investigated. The novel results showing the impact of using ferro-nanofluids in the two applications under consideration are presented. The results under special cases are further compared with the existing results in the literature and are found to agree well.

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