Aggregate Intensification of Natural Convection Between Air and a Vertical Parallel-Plate Channel by Inserting an Auxiliary Plate at the Mouth and Appending Colinear Insulated Plates at the Exit

2000 ◽  
Author(s):  
Assunta Andreozzi ◽  
Oronzio Manca ◽  
Antonio Campo
Keyword(s):  
Nusselt Number ◽  
Parallel Plate ◽  
Navier Stokes ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Heated Plate ◽  
Computational Domain ◽  
Plate Height ◽  
Pressure Profiles ◽  
Plate Channel

Abstract This paper addresses the examination of heat transfer in parallel-plate channels using a combination of two passive schemes: (1) the insertion of an auxiliary plate at the mouth and (2) the appendage of colinear insulated plates at the exit. The investigation is made by numerically solving the full elliptic Navier-Stokes and energy equation in a I-type computational domain. The channel is symmetrically heated by uniform heat flux. The working fluid is air. The results are reported in terms of induced mass flow rate and maximum wall temperatures. Further, the local Nusselt number, the mean Nusselt number and pressure profiles are presented. The analyzed Grashof numbers based on the heated plate height are 103 and 106.

Features of Natural Convective Air Flows Inside Vertical Parallel-Plate Channels Subject to Step Heat Fluxes: Insulated Upstream and Heated Downstream

1999 ◽  
Author(s):  
Antonio Campo ◽  
Oronzio Manca ◽  
Biagio Morrone
Keyword(s):  
Parallel Plate ◽  
Heat Fluxes ◽  
Uniform Heat Flux ◽  
Temperature Profiles ◽  
Computational Domain ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Velocity Pressure ◽  
The Impact ◽  
Plate Channel

Abstract This paper addresses the impact of adding insulated extensions at the entrance of a parallel-plate channel in which the plates receive a uniform heat flux and a natural convection air flow is responsible for the cooling. The full elliptic conservation equations are solved numerically in a composite I-type computational domain. It was found that the wall temperatures increase when the channel extensions are appended at the inlet. The pertinent results are reported in terms of maximum wall temperatures, induced mass flow rates, as well as velocity, pressure and temperature profiles of the fluid.

scholarly journals An empirical correlation for isothermal parallel plate channel completely filled with porous media

2013 ◽  
Vol 17 (4) ◽  
pp. 1061-1070 ◽  
Author(s):  
Mohammad Hamdan
Keyword(s):  
Porous Media ◽  
Nusselt Number ◽  
Steady State ◽  
Friction Factor ◽  
Parallel Plate ◽  
Empirical Correlation ◽  
Empirical Correlations ◽  
Fully Developed Flow ◽  
Forchheimer Model ◽  
Plate Channel

This study reports a simple empirical correlation for friction factor and Nusselt number for laminar, steady state, hydraulically and thermally fully developed flow in isothermal parallel plate channel completely filled with porous media. The study is carried out using a finite difference numerical analysis. The Darcy-Brinkman-Forchheimer model is used to model the flow inside the porous media. The empirical correlations are developed to relate friction factor and Nusselt number to Darcy and Forchheimer coefficient.

Thermal Modeling of Forced Convection in a Parallel-Plate Channel Partially Filled With Metallic Foams

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
H. J. Xu ◽  
Z. G. Qu ◽  
T. J. Lu ◽  
Y. L. He ◽  
W. Q. Tao
Keyword(s):  
Heat Transfer ◽  
Parallel Plate ◽  
Temperature Fields ◽  
Metallic Foam ◽  
Navier Stokes ◽  
Metallic Foams ◽  
Navier Stokes Equation ◽  
Coupling Conditions ◽  
Similar Work ◽  
Plate Channel

Fully developed forced convective heat transfer in a parallel-plate channel partially filled with highly porous, open-celled metallic foam is analytically investigated. The Navier–Stokes equation for the hollow region is connected with the Brinkman–Darcy equation in the foam region by the flow coupling conditions at the porous–fluid interface. The energy equation for the hollow region and the two energy equations of solid and fluid for the foam region are linked by the heat transfer coupling conditions. The normalized closed-form analytical solutions for velocity and temperature are also obtained to predict the flow and temperature fields. The explicit expression for Nusselt number is also obtained through integration. A parametric study is conducted to investigate the influence of different factors on the flow resistance and heat transfer performance. The analytical solution can provide useful information for related heat transfer enhancement with metallic foams and establish a benchmark for similar work.

Natural Convective Heat Transfer From a Narrow Isothermal Vertical Flat Plate With a Uniform Heat Flux at the Surface

2007 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Jane T. Paul
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Vertical Plate ◽  
Three Dimensional ◽  
Uniform Heat Flux ◽  
Heated Plate ◽  
Dimensional Flow ◽  
Uniform Heat ◽  
Two Dimensional Flow ◽  
The Mean

Natural convective flow over a vertical plate with a uniform heat flux over its surface has been numerically studied. When the plate is wide compared to its height the flow can be adequately modeled by assuming two-dimensional flow. However, when the width of the plate is relatively small compared to its height, the heat transfer coefficient can be considerably greater than that predicted by these two-dimensional flow results. The Nusselt number distribution over a narrow vertical plate, with a uniform heat flux at the plate surface, has been numerically determined. This heated plate is embedded in a plane adiabatic surface, the surface of the adiabatic surface being in the same plane as the heated plate. It has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. It has also been assumed that the flow is symmetrical about the vertical centre-plane of the plate. The solution has been obtained by numerically solving the full three-dimensional form of the governing equations, these equations being written in dimensionless form. The solution has the Rayleigh number, the dimensionless plate width and the Prandtl number as parameters. Results have been numerically determined for a relatively wide range of Rayleigh numbers and dimensionless plate widths for a Prandtl number of 0.7. The dimensionless plate width has been found to have a significant influence on the mean Nusselt number for the plate when the plate is narrow and the Rayleigh number is low. The conditions under which three dimensional flow effects can be neglected have been deduced and an empirical equation for the mean Nusselt number for narrow plates with a uniform surface heat flux has been derived from the numerical results.

scholarly journals Slip Velocity Distribution in a Parallel Plate Channel on Asymmetric Thermal Boundary Condition

2016 ◽  
Vol 35 ◽  
pp. 113-126
Author(s):  
Md Tajul Islam
Keyword(s):  
Boundary Conditions ◽  
Velocity Distribution ◽  
Parallel Plate ◽  
Control Volume ◽  
Navier Stokes ◽  
Working Fluid ◽  
Slip Boundary Conditions ◽  
Cross Sectional ◽  
Slip Boundary ◽  
Knudsen Numbers

Steady, laminar and fully developed flows in parallel plate microchannel with asymmetric thermal wall conditions are solved by control volume technique. In order to examine the influence of Reynolds number and Knudsen number on the velocity distributions, a series of simulations are performed for different Reynolds and Knudsen numbers. Nitrogen gas is used as working fluid and we assume the fluid as continuum but employ the slip boundary conditions on the walls. The Navier-Stokes and energy equations are solved simultaneously. The results are found in good agreement with those predicted by analytical solutions in 2D continuous flow model employing first order slip boundary conditions. It is concluded that the rarefaction flattens the velocity distribution. If the product of Reynolds numbers and Knudsen numbers is fixed, the cross sectional average velocity is fixed for incompressible flow.GANIT J. Bangladesh Math. Soc.Vol. 35 (2015) 113-126

Mixed Convection in an Impinging Laminar Single Square Jet

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
L. B. Y. Aldabbagh ◽  
A. A. Mohamad
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Richardson Number ◽  
Vortex Motion ◽  
Navier Stokes ◽  
Heated Plate ◽  
Calculation Results ◽  
Single Jet ◽  
Energy Equations ◽  
Target Spacing

The effect of Richardson number (Ri=Gr/Re2=Ra/Pr Re2) in a confined impinging laminar square jet was investigated numerically through the solution of Navier–Stokes and energy equations. The simulations were carried out for Richardson number between 0.05 and 8 and for jet Reynolds number between 50 and 300. The jet-to-target spacings were fixed to 0.25B, 0.5B, and 1.0B, respectively, where B is the jet width. The calculation results show that for the jet-to-target spacing of 0.25B, the flow structure of a square single jet impinging on a heated plate is not affected by the Richardson number. For such very small jet-to-target distances the jet is merely diverted in the transverse direction. The wall jet fills the whole gap between the plates with a very small vortex motion formed near the corners of the jet cross section close to the upper plate. In addition, the effect of the Richardson number on the variation in the local Nusselt number is found to be not significant. For higher jet-to-target spacing, the Nusselt number increased as the Richardson number increased for the same Re. In addition, the heat transfer rate increased as the jet Reynolds number increased for the same Richardson number.

Laminar Heat Transfer in a Parallel Plate Channel With Solid and Porous Baffles

2004 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Nicolau B. Santos
Keyword(s):  
Laminar Flow ◽  
Parallel Plate ◽  
Control Volume ◽  
Computational Domain ◽  
Control Volume Method ◽  
Algebraic Equations ◽  
Simple Method ◽  
Volume Method ◽  
Plate Channel ◽  
Elementary Representative Volume

Simulations are presented for laminar flow in a channel containing fins made with solid (impermeable) and porous materials. The equations of mass continuity, momentum and energy are written for an elementary representative volume yielding a set of equations valid for the entire computational domain. These equations are discretized using the control volume method and the resulting system of algebraic equations is relaxed with the SIMPLE method. The presented numerical results for the friction factor f and the Nusselt number Nu were compared with available data indicating that results herein differ by less than 5% in relation to published results. Further simulations comparing the effectiveness of the porous material used showed that no advantages are obtained for using low porosity baffles in the laminar flow regime.

Numerical Analysis of Condensation of R134a in a Single Microchannel

2012 ◽  
Author(s):  
Harish Ganapathy ◽  
Amir Shooshtari ◽  
Kyosung Choo ◽  
Serguei Dessiatoun ◽  
Mohamed Alshehhi ◽  
...  
Keyword(s):  
Nusselt Number ◽  
Pressure Drop ◽  
Predictive Accuracy ◽  
Flow Patterns ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Computational Domain ◽  
Two Phase ◽  
Qualitative Comparison ◽  
Frictional Pressure Drop

The present work proposes a numerical, transient modeling approach for the simulation of condensation heat transfer in a single microchannel. The model was based on the volume of fluid approach, which governed the hydrodynamics of the two-phase flow. User-defined routines were implemented in order to simulate the effects of condensation, which included mass transfer at the liquid-vapor interface and the associated release of latent heat. A channel having hydraulic diameter of 100 micrometer was modeled using a two-dimensional computational domain. The working fluid was R134a and the vapor mass fluxes at the channel inlet ranged from 245 to 615 kg/m2s. The channel wall was maintained at a constant heat flux, ranging between 200 to 800 kW/m2. The predictive accuracy of the numerical model was assessed by comparing the two-phase frictional pressure drop and Nusselt number with the available empirical correlations in the literature. A reasonably good agreement was obtained for both parameters with mean absolute errors as low as ±7.5% for pressure drop and ±15.6% for Nusselt number. Further, a qualitative comparison of various flow patterns against experimental visualization data was performed. The predicted flow patterns were classified based on the relative dominance of surface tension and inertia forces, and the results were in close agreement with visualization data. On the whole, the newly developed approach was found to have a high predictive accuracy with respect to the simulation of condensation phenomena in microscale domains and was concluded to be a useful tool in support of the design and optimization of advanced microchannel-based heat exchangers.

Heat Transfer to Laminar Flow in Tapered Passages

1965 ◽  
Vol 32 (3) ◽  
pp. 684-689 ◽  
Author(s):  
E. M. Sparrow ◽  
J. B. Starr
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Wall Temperature ◽  
Parallel Plate ◽  
Laminar Flows ◽  
Wall Heat Flux ◽  
Heat Transfer Analysis ◽  
Plate Channel

Consideration is given to the fully developed heat-transfer characteristics of laminar flows in converging and diverging plane-walled passages. The analysis is carried out for the two fundamental thermal boundary conditions of prescribed wall heat flux and prescribed wall temperature. As a prelude to the heat-transfer analysis, a new solution for the velocity distribution is derived on the basis of a linearized momentum equation. The Nusselt number for flow in tapered passages is found to depend on the Reynolds number; this is in contrast to the situation for passages of longitudinally unchanging cross section wherein the Nusselt number is independent of the Reynolds number. In general, the Nusselt number for flow in a plane-walled diverging passage falls below that for the parallel-plate channel, while the Nusselt number for a converging flow is usually higher than that for a parallel-plate channel. Moreover, the fully developed Nusselt numbers for prescribed wall heat flux exceed those for prescribed wall temperature.

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