Combined Forced and Free Laminar Convection in the Entrance Region of an Inclined Isothermal Tube

1988 ◽  
Vol 110 (4a) ◽  
pp. 901-909 ◽  
Author(s):  
D. Choudhury ◽  
S. V. Patankar
Keyword(s):  
Numerical Results ◽  
Entrance Region ◽  
Heat Transfer Characteristics ◽  
Local Pressure ◽  
Flow And Heat Transfer ◽  
Developing Flow ◽  
Free And Forced Convection ◽  
Laminar Convection ◽  
Independent Parameters ◽  
Axial Development

An analysis is made of the combined forced and free convection for laminar flow in the entrance region of isothermal, inclined tubes. This involves the numerical calculation of the developing flow with significant buoyancy effects. Three independent parameters are introduced: the Prandtl number Pr, a modified Rayleigh number Ra*, and Ω, a parameter that measures the relative importance of free and forced convection. The inclination angle does not appear explicitly in the formulation. Numerical results are obtained for Pr = 0.7, 5, and 10, and representative values of Ra* and Ω. The axial development of the velocity profiles, temperature field, local pressure gradient, and the Nusselt number are presented. These results reveal that the buoyancy effects have a considerable influence on the fluid flow and heat transfer characteristics of the development flow. A comparison of the numerical results with the available experimental data is also presented.

Cooling of a Vertical Shrouded Fin Array by Natural Convection: A Numerical Study

1987 ◽  
Vol 109 (3) ◽  
pp. 671-676 ◽  
Author(s):  
K. C. Karki ◽  
S. V. Patankar
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Bulk Temperature ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Developing Flow ◽  
Laminar Natural Convection ◽  
System Geometry ◽  
Chimney Effect ◽  
Axial Development

An analysis is made of the laminar natural convection in a vertical shrouded fin array, in which the flow is induced from the surroundings by the chimney effect. This involves the calculation of developing flow in a duct. The results are obtained numerically for representative values of the parameters describing the system geometry and ducts of different lengths. The axial development of various flow quantities, such as the Nusselt number and the bulk temperature, has been presented. In addition, the overall flow and heat transfer characteristics have been discussed.

Turbulent Flow and Heat Transfer in the Entrance Region of a Parallel Wall Passage

1969 ◽  
Vol 184 (1) ◽  
pp. 697-712 ◽  
Author(s):  
J. Byrne ◽  
A. P. Hatton ◽  
P. G. Marriott
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Entrance Region ◽  
Fully Developed Flow ◽  
Law Of The Wall ◽  
Flow And Heat Transfer ◽  
Developing Flow ◽  
Boundary Layer Development ◽  
Parallel Wall ◽  
Made In

Measurements of boundary layer development and heat transfer were made in the entrance region of a parallel passage and compared with a computer solution based on the law of the wall. Little difference was found between the heat transfer, both measured and predicted, with a developing flow and that predicted with a fully developed flow. The experiments also show that boundary layer parameters, such as momentum thickness, do not approach their fully developed values asymptotically.

Natural Convection of Nanofluid in a Triangle Cavity with Different Angular Positions

2020 ◽  
Vol 12 (3) ◽  
pp. 325-329
Author(s):  
Mohsen Rostami ◽  
Mohammad Saleh Abadi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Natural Convection ◽  
Flow Field ◽  
Boundary Conditions ◽  
Angular Position ◽  
Numerical Results ◽  
Heat Transfer Characteristics ◽  
Current Structure ◽  
Flow And Heat Transfer

The effects of the angular position on the flow and heat transfer of the nanofluid in a triangular cavity is investigated numerically. A triangular cavity is chosen with the same boundary conditions as the published results are available. The comparison between the current numerical results with the available data is made to show the accuracy of the numerical simulation. The current structure of triangular cavity is rotated to investigate the effects of various angular positions on the flow and heat transfer characteristics of nanofluid. For this purpose, the equations of continuity, momentum and energy are solved numerically. The results show that the hot fluid is more freely penetrated into the domain by increasing of the angular position. The velocity of fluid in the flow field becomes maximum for the angle of 120 . Also, the creation of vortices in the flow field depends on the value of angular position.

Combined Forced and Free Convection in the Entrance Region of an Isothermally Heated Horizontal Pipe

1982 ◽  
Vol 104 (1) ◽  
pp. 153-159 ◽  
Author(s):  
Mikio Hishida ◽  
Yasutaka Nagano ◽  
M. S. Montesclaros
Keyword(s):  
Numerical Solutions ◽  
Entrance Region ◽  
Temperature Fields ◽  
Horizontal Pipe ◽  
Uniform Wall Temperature ◽  
Nusselt Numbers ◽  
Developing Flow ◽  
Uniform Wall ◽  
Secondary Velocity ◽  
Laminar Convection

Numerical solutions are given without the aid of a large Prandtl number assumption for combined forced and free laminar convection in the entrance region of a horizontal pipe with uniform wall temperature. The steady-state solutions have been obtained from the asymptotic time solutions of the time-dependent equations of momentum and energy with the Poisson equation for pressure. Results are presented for the developing primary and secondary velocity profiles, developing temperature fields, local wall shear stress, and local and average Nusselt numbers, which reveal how the developing flow and heat transfer in the entrance region are affected by the secondary flow due to buoyancy forces.

Numerical Investigation of Flow and Heat Transfer in Microchannels

2008 ◽  
Author(s):  
Emrah Deniz ◽  
I. Yalcin Uralcan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Experimental Studies ◽  
Numerical Results ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Micro Channels

Mini and microchannel applications have become an important and attractive research area during the past decades. For micro systems design purposes, numerical and experimental studies have been conducted on flow and heat transfer characteristics of mini and microchannels and various friction factor and Nusselt number correlations have been proposed. Some researchers have tried to apply conventional tube correlations to mini and micro channels, rather than deriving new correlations. In this study, using commercial CFD software, flow and heat transfer characteristics in laminar and turbulent flow through circular channels are analyzed numerically. The applicability of conventional correlations in calculating the friction factor and Nusselt number is investigated. It is concluded that, in laminar regime conventional correlations can be used to calculate the friction factor for the channel sizes considered. In turbulent regime, however, numerical results for friction factor yielded greater values than those calculated by the conventional correlations. Numerical Nusselt numbers are found to be closer to the conventional values in laminar and turbulent regimes. In turbulent regime, on the other hand, Nusselt number values calculated with the microchannel correlations are determined to be greater than the numerical results and the values calculated with the conventional correlations.

Forced Convection Flow in a Wavy Channel With a Linearly Increasing Waviness at the Entrance Region

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Esam M. Alawadhi
Keyword(s):  
Pressure Drop ◽  
Thermal Characteristics ◽  
Reynolds Numbers ◽  
Entrance Region ◽  
Convection Flow ◽  
Wavy Wall ◽  
The Finite Element Method ◽  
Wavy Channel ◽  
Flow And Heat Transfer ◽  
Developing Flow

This research studies the fluid flow and heat transfer in a wavy channel with a linearly increasing waviness at the entrance region. The considered model consists of a channel formed by two wavy plates described by a sinusoidal profile and maintained at a uniform temperature. The finite element method is utilized to solve the problem. Reynolds numbers are considered in the range of 125<Re<1000 to avoid unsteady flow, and Pr=0.7. The global objective of this research is to reduce the pressure drop in the wavy channel due to the developing flow at the entrance region. The effect of the Reynolds number, length of the increasing waviness region, waviness of the wavy wall on the hydrodynamics, and thermal characteristics of the channel is investigated. The result indicates that the linearly increasing waviness at the entrance region significantly reduces the pressure drop in the channel on the other hand, the thermal characteristics of the wavy wall are nearly unaffected.

scholarly journals A Numerical Analysis on Flow and Heat Transfer in the Entrance Region of an Axially Rotating Pipe

1995 ◽  
Vol 2 (2) ◽  
pp. 123-129 ◽  
Author(s):  
Shuichi Torii ◽  
Wen-Jei Yang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Numerical Study ◽  
Turbulence Models ◽  
Axial Rotation ◽  
Entrance Region ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Radial Profiles ◽  
Thermal Development

A numerical study is performed to investigate turbulent flow and heat transfer characteristics in the entrance region of a pipe rotating around its axis. Various different k-ε turbulence models are employed whose function consists of the Richardson number in the e model to take swirling into account. The axial rotation of the pipe suppresses thermal development and causes a substantial decrease in the Nusselt number along the flow. It is disclosed from the study that an increase in the rotation rate induces a reduction in the velocity gradient, turbulent kinetic energy and Reynolds stress in the vicinity of the wall and a substantial deformation of these radial profiles in the downstream direction. It results in both a suppression of the thermal development and an attenuation in the Nusselt number along the flow.

Analysis of Flow and Heat Transfer Characteristics Around an Oval-Shaped Cylinder

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Guan-Min Zhang ◽  
Mao-Cheng Tian ◽  
Nai-Xiang Zhou ◽  
Wei Li ◽  
David Kukulka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Gradient ◽  
Transfer Coefficient ◽  
Angular Position ◽  
Numerical Results ◽  
Heat Transfer Characteristics ◽  
Axis Ratio ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Numerical simulations and experimental study were carried out to investigate the flow and heat transfer characteristics of air flowing across different types of oval-shaped cylinders, for Reynolds numbers varying from 4000 to 50,000. These cylinders have axis ratios, ε, of 1, 1.5, 2, 3, 4, and 5 with the major axis parallel to the free-stream. Numerical results show the closer the distance to mainstream, the smaller the local velocity gradient is. The angular position of the minimum value of Cp decreases as ε decreases and the maximum value of Cf gradually increases with ε increasing. Oval-shaped cylinders have a higher favorable pressure gradient at the front of the cylinder and a lower adverse pressure gradient at the back of the cylinder for flows in inhibiting separation. Empirical correlations for each tube have been obtained by numerical simulation relating the dimensionless heat transfer coefficient with the Reynolds Number and Prandtl Number. Based on the presented results, it can be emphasized that the average heat transfer coefficient firstly increases and then decreases by increasing the axis ratio of the tube, implying that the elliptical tubes with a suitable axis ratio possess more advantages over circular tubes. Comparisons of the numerical results with the existing data verify the validation of the present study.

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