Investigation of heat transfer in square porous-annulus (original) (raw)
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Analysis of flow and heat transfer in porous media imbedded inside various-shaped ducts
2004
Heat transfer to a fluid passing through a channel filled with porous materials is the subject of this investigation. It includes the derivation of the temperature solutions in channels having different cross sectional geometries. Primarily, consideration is given to a modified Graetz problem in parallel plate channels and circular tubes. This presentation includes numerical features of the exact series solution for these two ducts using the Brinkman's model.
Journal of University of Babylon for Engineering Sciences, 2019
This work presents experimental investigation of flow and heat transfer characteristics for entry length of turbulent flow in a rectangular duct fitted with porous media and air as the working fluid. Rectangular duct (300×30 mm) with a hydraulic diameter (54.54 mm) was subjected to constant heat flux from lower surface (1.5 ×10 2-1.8 ×10 2 w/m 2) and Reynolds number ranged (3.3x10 4 up to 4.8x10 4). Copper mesh inserts (as porous media) with screen diameter (54.5 mm) for vary distance between two adjacent screens of (10 mm), (15 mm) and (20 mm) in the porosity range of (0.98-0.99) are considered for experimentation. The effect of porous height ratio (full and partial) are also considered. It is observed that the enhancement of heat transfer by using mesh inserts when compared to a plain surface is more by a factor of (2.2) times where the skin fraction coefficient is about (5) times. An Empirical correlation for Nusselt number and friction factor are developed for the mesh inserts from the obtained results.
International Journal of Heat and Mass Transfer, 1995
An analytical solution is obtained for a fully developed, forced convection in a gap between two concentric cylinders. The inner is exposed to a constant heat flux and the outer is thermally insulated. A porous layer is attached to the inner cylinder. The effects of the permeability, thermal conductivity and the thickness of the porous material are investigated using a Brinkman+xtended Darcy model. It is shown that there exists a critical thickness of the porous layer at which heat transfer is minimum in the case of low thermal conductivity materials, while this does not show for highly conducting materials. The obtained results show that increasing either the permeability or the thermal conductivity improves the heat transfer. Further, for highly permeable and conducting porous media, it may not be necessary to fill the gap completely to attain the maximum heat transfer.
Convection Heat Transfer in a Channel of Different Cross Section Filled with Porous Media
Kufa journal of Engineering, 2018
A forced convection heat transfer in ducts (circular, triangular, rectangular) cross sections and (1m) length with hydraulic diameter (0.1m) filled with porous media (glass spheres 12 mm diameter) is investigated experimentally at constant heat flux from the wall (1070W/m²) with Reynolds number range of (12461-2500). Comparison was made between three ducts for local temperature distribution and local Nusselt number). The experimental results showed the effect of Reynolds number and cross section on the temperature profile and local Nusselt number,also empirical correlations for average Nusselt number and Peclet number were obtained for three ducts. http://dx.doi.org/10.30572/2018/kje/090205
The effect of aspect ratio on heat transfer in a square cavity filled with a porous medium
IOP Conference Series: Materials Science and Engineering, 2020
Two dimensional mathematical model of an enclosure filled with a porous medium and heated from the lower end with various values of the width to height ratio (aspect ratio) has been studied in the present article. A two dimensional free convection model has been solved numerically using finite difference technique to evaluate the streamlines, isotherm lines, and the average Nusslet number. The set values where; Rayleigh number of 106, Prandtl number of 0.72, and aspect ratio ranging from 1:4 to 4:1. The model has been validated and the results showed that the aspect ratio has a clear effect on the average Nusselt number and that increasing the flow rate for aspect ratio form 1:4 to 4:1.
Numerical Study of Heat Transfer Coefficient in Porous Media
2009
⎯ In this study, convective heat transfer in a porous flat plate channel flow is simulated by a direct numerical method. The solid materials consist of uniform distributed blocks, which resemble the porous medium within the channel. The solid materials are assumed to be isothermal and the channel walls are under adiabatic conditions. The Navier–Stokes equations are solved directly in the fluid region without the assumption of volume averaging. The two energy transport equations are solved for the solid and fluid flow separately. The results indicate that the mean bulk temperature across the channel develops faster if the channel aspect ratio gets smaller. On the other hand, the Nusselt number has the highest value at the channel inlet and gradually approaches to a minimum or developing condition at a distance which depends on the value of the aspect ratio.
International Communications in Heat and Mass Transfer, 2016
Laminar natural convection heat transfer in a differentially heated cavity with two thin porous fins attached to the hot wall and bottom insulated surface was studied numerically for various pertinent parameters. Such parameters include Richardson number, Darcy number, thermal conductivity ratio, and location of the porous fin. The left wall of the cavity is assumed to be uniformly heated while the right wall is kept at a lower temperature. In addition, the horizontal walls of the cavity were considered insulated. Furthermore, the governing transport equations within the porous media were written according to the volume-average theory. The governing equations are solved using a finite element formulation based on the Galerkin method of weighted residuals. The results of this investigation showed that the presence of a horizontal porous fin increases the average Nusselt number when compared with the differentially heated cavity for various Richardson numbers and thermal conductivity ratios. However, a vertical porous fin attached to the bottom insulated surface exhibited a lower average Nusselt number than the no-fin case.
The conjugate natural convection heat transfer in a partially heated square porous enclosure had been studied numerically. The governing dimensionless equations are solved using COMSOL Multiphysics and Darcy model assumed to be used. The considering dimensionless parameters are modified Rayleigh number, finite wall thickness, thermal conductivity ratio and the heat source length. The results are presented in terms of streamlines, isotherms and local and average Nusselt number. The results indicate that; the heat transfer can be enhanced by increasing the modified Rayleigh number. When the heat source length increases, the local Nusselt number of fluid phase increases, while, a reverse behavior of the local Nusselt number along the heat source is found. As the Rayleigh number increase, the local Nusselt number for both fluid and solid phase increases, therefore, the heat transfer rate will be enhanced. On the other hand, when the thermal conductivity ratio increase, the local Nusselt number for the fluid phase increases, and the local Nusselt number along the heated wall decreases.