UNSTEADY FORCED CONVECTION FOR A DEVELOPING FLOW IN A NON SYMMETRIC PERIODIC CHANNEL

Equipment ◽  
2006 ◽  
Author(s):  
R. Creff ◽  
P. Le Quere ◽  
S. Blancher
Keyword(s):  
Forced Convection ◽  
Developing Flow

Free-Forced Convection in the Entry Region of a Heated Straight Pipe

1978 ◽  
Vol 100 (2) ◽  
pp. 212-219 ◽  
Author(s):  
Lun-Shin Yao
Keyword(s):  
Boundary Layer ◽  
Forced Convection ◽  
Axial Velocity ◽  
Convection Boundary Layer ◽  
Fluid Temperature ◽  
Straight Pipe ◽  
Horizontal Pipe ◽  
Core Flow ◽  
Developing Flow ◽  
Axial Pressure Gradient

The developing flow in the entry region of a horizontal pipe whose temperature is held constant and higher than the entry fluid temperature is analyzed. The asymptotic solution of the developing flow near the entrance of the heated straight pipe, distance 0(a), is obtained by perturbing the solution of the developing flow in an unheated straight pipe. The displacement of the boundary layer induces radial-directional and downward motion of the fluid particles in the inviscid core flow. The combination of these two motions results in two vortices developing along the pipe. The temperature in the core flow equals the entry fluid temperature. The forced convection boundary layer is affected by the buoyancy force and the axial pressure gradient induced by the boundary-layer displacement, and so is the heat transfer rate. The axial velocity has a concave profile with its maximum off the center line near the entrance, and it grows toward a uniformly distributed profile downstream. The downward stream caused by the displacement of the secondary boundary layer forces the axial velocity profile to turn counterclockwise continuously along the pipe if the flow is from left to right. The competition of two displacement effects supplies the physical explanation of why the flow pattern and the temperature distribution in heated pipes differ due to different degrees of heating.

Forced Convection in the Entrance Region of a Packed Channel With Asymmetric Heating

1988 ◽  
Vol 110 (4a) ◽  
pp. 946-954 ◽  
Author(s):  
P. Cheng ◽  
C. T. Hsu ◽  
A. Chowdhury
Keyword(s):  
Forced Convection ◽  
Closed Form Solution ◽  
Form Solution ◽  
Wall Effect ◽  
Thermal Dispersion ◽  
Variable Porosity ◽  
Developing Flow ◽  
Lateral Mixing ◽  
Forced Convective Flow ◽  
Asymmetric Heating

The problem of a thermally developing forced convective flow in a packed channel heated asymmetrically is analyzed in this paper. The flow in the packed channel is assumed to be hydrodynamically fully developed and is governed by the Brinkman–Darcy–Ergun equation with variable porosity taken into consideration. A closed-form solution based on the method of matched asymptotic expansions is obtained for the axial velocity distribution, and the wall effect on pressure drop is illustrated. The energy equation for the thermally developing flow, with transverse thermal dispersion and variable stagnant thermal conductivity taken into consideration, was solved numerically. To match the predicted temperature distributions with existing experimental data, it is found that a wall function must be introduced to model the transverse thermal dispersion process in order to account for the wall effect on the lateral mixing of fluid. The variations of the local Nusselt number along the streamwise direction in terms of the appropriate parameters are illustrated. The thermal entrance length effect on forced convection in a packed channel is discussed.

scholarly journals Leveque-Type Similarity Transformation for a Thermally Developing Viscous Dissipative Flow in a Parallel Plate Channel

2021 ◽  
Vol 39 (4) ◽  
pp. 1389-1394
Author(s):  
Gooi Mee Chen ◽  
Yew Hau Yip
Keyword(s):  
Heat Flux ◽  
Forced Convection ◽  
Parallel Plate ◽  
Similarity Transformation ◽  
Axial Direction ◽  
Transformation Method ◽  
Uniform Heat Flux ◽  
Practical Applications ◽  
Developing Flow ◽  
Plate Channel

Compared to the existing more elaborate eigenvalues-eigenfunction analytical solution where the solution of a thermally developing forced convection problem converges very slowly at the beginning of thermal entrant region, Leveque-type similarity transformation method provides a more convenient way to look into the insights of the problem. Assuming that the wall heat flux and viscous dissipation only has an effect within the thin thermal boundary layer at the beginning of the thermal entrance region, this study intends to solve the governing thermal energy equation for a thermally developing flow in a parallel plate channel, subjected to uniform heat flux, by means of Leveque-type similarity transformation. The resulting ordinary differential equation, is subsequently solved by a fourth order Runge Kutta method. A comparison of the Nusselt number along the axial direction, at the beginning of the thermally developing region with the literature, reveals less than 10% discrepancy for Brinkman number less than one, which is a commonly acceptable range for practical applications. Although its accuracy depletes downstream the channel, similarity transformation provides sufficiently accurate temperature distribution, and captures the heat transfer insights for a thermally developing viscous dissipative forced convection.

scholarly journals General Correlations for Laminar Flow Friction Loss and Heat Transfer in Plain Rectangular Plate-Fin Cores

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Kuan-Ting Lin ◽  
Dantong Shi ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Forced Convection ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Cross Sectional ◽  
Core Flow ◽  
Developing Flow ◽  
Flow Length ◽  
Fanning Friction Factor

Abstract New generalized correlations for predicting the average fanning friction factor f and average Nusselt number Nu for laminar flow in plain plate-fin compact cores of rectangular cross section are presented. These are based on extended experimental data, as well as three-dimensional computational simulations, obtained for a broad range of fin density and geometrical attributes. The results indicate that while the fully developed forced convection scales only with the interfin channel cross-sectional ratio α (fin spacing by fin height), the entrance region hydrodynamic and thermal performance is additionally a function of the fin-core length L, flow Reynolds number Re, and fluid Prandtl number Pr. The developing flow and convection is further shown to scale as: (fRe)∼(L/dhRe)1/2, and Nu ∼(L/dhRe)1/2Pr1/3ϕ(α), where f, Re, and Nu are all based on the hydraulic diameter dh of the interfin flow channel. Generalized correlations for both (fRe) and Nu are developed by the corresponding scaling of the forced convection behavior and asymptotic matching of the entrance or developing flow (short fin-core flow length) and the fully developed flow (large fin-core flow length) region performance. Finally, the predictions from these correlations are found to be within ±15% of all available experimental data for air, water, and glycol (0.71 ≤ Pr ≤ 10), and fin cores with 0 < α ≤ 1.

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