scholarly journals Effect of an inserted porous layer on heat and fluid flow in a vertical channel with mixed convection

2015 ◽  
Vol 19 (3) ◽  
pp. 1005-1016 ◽  
Author(s):  
Hasan Celik ◽  
Moghtada Mobedi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Pressure Drop ◽  
Mixed Convection ◽  
Porous Layer ◽  
Convection Heat Transfer ◽  
Vertical Channel ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Transfer Condition

Temperature and velocity fields in a vertical channel partially filled with porous medium under mixed convection heat transfer condition are obtained. The heat transfer equation and equation of motion for clear and porous layer regions are written and solved analytically. The nondimensionalization of the governing equations yields two Grashof numbers as Grc and Grd for clear and porous sections where Grd=Da.Grc. The dimensionless governing parameters for the problem are Grc (or Grd), Da, thermal conductivity ratio (i.e., K) and thickness of porous layer. The temperature and velocity profiles for different values of Grc, Da, K and thickness of porous layer are plotted and their changes with the governing parameters are discussed. Moreover, the variation of pressure drop with the governing parameters is investigated. The decrease of porous layer thickness or thermal conductivity ratio increases the possibility of the downward flows. Thermal conductivity ratio plays important role on pressure drop, particularly for the channels with high values of Grc/Re.

Upward and downward conjugate mixed convection heat transfer in a partially porous cavity

2016 ◽  
Vol 26 (1) ◽  
pp. 159-188 ◽  
Author(s):  
Abderrahim Bourouis ◽  
Abdeslam Omara ◽  
Said Abboudi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mixed Convection ◽  
Transfer Rate ◽  
Vertical Wall ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Content Type ◽  
Moving Wall ◽  
The Right

Purpose – The purpose of this paper is to provide a numerical study of conjugate heat transfer by mixed convection and conduction in a lid-driven enclosure with thick vertical porous layer. The effect of the relevant parameters: Richardson number (Ri=0.1, 1, 10) and thermal conductivity ratio (Rk=0.1, 1, 10, 100) are investigated. Design/methodology/approach – The studied system is a two dimensional lid-driven enclosure with thick vertical porous layer. The left vertical wall of the enclosure is allowed to move in its own plane at a constant velocity. The enclosure is heated from the right vertical wall isothermally. The left and the right vertical walls are isothermal but temperature of the outside of the right vertical wall is higher than that of the left vertical wall. Horizontal walls are insulated. The governing equations are solved by finite volume method and the SIMPLE algorithm. Findings – From the finding results, it is observed that: for the two studied cases, heat transfer rate along the hot wall is a decreasing function of thermal conductivity ratio irrespective of Richardson numbers contrary to the heat transfer rate along the fluid-porous layer interface which is an increasing function of thermal conductivity ratio. At forced convection dominant regime, the difference between heat transfer rate for upward and downward moving wall is insensitive to the thermal conductivity ratio. For downward moving wall, average Nusselt number is higher than that of upward moving wall. Practical implications – Some applications: building applications, furnace design, nuclear reactors, air solar collectors. Originality/value – From the bibliographic work and the authors’ knowledge, the conjugate mixed convection in lid-driven partially porous enclosures has not yet been investigated which motivates the present work that represent a continuation of the preceding investigations.

Conjugate Nusselt Numbers for Simultaneously Developing Flow Through Rectangular Ducts

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Georgios Karamanis ◽  
Marc Hodes
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Extended Surface ◽  
Side Walls ◽  
Extended Surfaces ◽  
Prandtl Numbers

We consider conjugate forced-convection heat transfer in a rectangular duct. Heat is exchanged through the isothermal base of the duct, i.e., the area comprised of the wetted portion of its base and the roots of its two side walls, which are extended surfaces within which conduction is three-dimensional. The opposite side of the duct is covered by an adiabatic shroud, and the external faces of the side walls are adiabatic. The flow is steady, laminar, and simultaneously developing, and the fluid and extended surfaces have constant thermophysical properties. Prescribed are the width of the wetted portion of the base, the length of the duct, and the thickness of the extended surfaces, all three of them nondimensionalized by the hydraulic diameter of the duct, and, additionally, the Reynolds number of the flow, the Prandtl number of the fluid, and the fluid-to-extended surface thermal conductivity ratio. Our conjugate Nusselt number results provide the local one along the extended surfaces, the local transversely averaged one over the isothermal base of the duct, the average of the latter in the streamwise direction as a function of distance from the inlet of the domain, and the average one over the whole area of the isothermal base. The results show that for prescribed thermal conductivity ratio and Reynolds and Prandtl numbers, there exists an optimal combination of the dimensionless width of the wetted portion of the base, duct length, and extended surface thickness that maximize the heat transfer per unit area from the isothermal base.

Lattice Boltzmann simulation of conjugate forced convection in a channel heat sink with surface-mounted blocks

2019 ◽  
Vol 97 (12) ◽  
pp. 1332-1341
Author(s):  
Haifeng Zhang ◽  
Dinggen Li ◽  
Peixin Ye ◽  
Zihao Yu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Pressure Drop ◽  
Forced Convection ◽  
Lattice Boltzmann ◽  
Heat Sink ◽  
Thermal Conductivity Ratio ◽  
Geometrical Parameters ◽  
Conductivity Ratio ◽  
Aspect Ratios

The study of the conjugate forced convection in a channel has many practical applications and has attracted attention from researchers, although the conjugate heat transfer in this configuration is usually ignored. In this paper, the conjugate forced convection heat transfer in a channel heat sink with surface-mounted blocks is numerically studied with the lattice Boltzmann method. The effects of Reynolds numbers and geometrical parameters of the blocks in different aspect ratios on the flow field and temperature distribution for various thermal conductivity ratio of solid wall to the fluid are analyzed. The results reveal that the distributions of the vortices and streamlines in the channel heat sink largely depend on the geometric parameters, and the increase of the distance between two mounted blocks tends to cause the pressure drop to increase and the average Nusselt number decreases. In addition, we found that a modification of the thermal conductivity ratio of solid to fluid has little effect on the pressure drop, whereas the heat transfer performance becomes much better.

scholarly journals Thermal study of fluid flow inside an annular pipe filled with porous media under local thermal non-equilibrium condition

2019 ◽  
Vol 13 (2) ◽  
pp. 4880-4897
Author(s):  
Abdelkrim Bouaffane ◽  
Kamel Talbi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Biot Number ◽  
Convection Heat Transfer ◽  
Radius Ratio ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Convection Heat ◽  
Local Difference ◽  
Annular Pipe

The present work involves the thermal numerical simulation of fluid flow inside an annular pipe completely filled porous material. The mathematical model of the energy transport is based on the Local Thermal Non-Equilibrium (LTNE) between the fluid and the solid phases. The governing equations are discretized by the finite volume method. SIMPLE algorithm has been used to solve the set of algebraic discretized coupled equations. This work is divided in two parts. In the first part, the effect of the pertinent dimensionless parameters which govern the study such as Biot number (Bi), solid-fluid thermal conductivity ratio (Rc) and radius ratio (Rr) on the LTNE intensity are analyzed by calculating: the local difference of temperature (LDT), the maximum of the local difference of temperature (LDTmax) and the average of LDT. The results show that the increase of Biot number and the solid-fluid thermal conductivity ratio, and the decrease of radius ratio reduce the LTNE intensity. The intensity of the LTNE in the developing region is greater than that of the fully developed region. In the second part, the convection heat transfer enhancement is studied, the results illustrate that the increase of Biot number and the solid-fluid thermal conductivity ratio, and the decrease of radius ratio represent good factors to ameliorate the rate of the convection heat transfer between the fluid and the inner wall.

Effects of a centered conducting body on natural convection of non-Newtonian fluid in a square enclosure with time-periodic temperature distribution

2020 ◽  
Author(s):  
Peixin Ye ◽  
Dinggen Li ◽  
Zihao Yu ◽  
Haifeng Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Transient Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Transfer Ratio ◽  
Periodic Temperature ◽  
Power Law Index ◽  
Time Periodic

In this paper, a modified lattice Boltzmann model that incorporates the effect of heat capacity is adopted to study the effects of a centered conducting body on natural convection of non-Newtonian fluid in a square cavity with time-periodic temperature distribution. The effects of power-law index, Rayleigh number, heat capacity ratio, thermal conductivity ratio, body size, temperature pulsating period and the temperature pulsating amplitude on fluid flow and heat transfer are analyzed in detail. The results showed that the increase of Rayleigh number and thermal conductivity ratio as well as the decrease of power-law index can strengthen both transient and global heat transfer, while the increase of heat capacitance of fluid to the solid wall can only enhance the transient heat transfer, and has little effect on the overall heat transfer. Further, the increase of body size will reduce both the transient heat transfer ratio and the overall heat transfer ratio. In addition, the decrease of temperature pulsating period can enhance the transient heat transfer, but it will slightly weaken the overall heat transfer. Finally, the results show that both the transient and the overall heat transfer ratio are increased with the increase of temperature pulsating amplitude.

Assessment of Thermal Non-Equilibrium Condition on Heat Transfer through a Channel Lined with Porous Media – Constant Wall Temperature

2011 ◽  
Vol 312-315 ◽  
pp. 33-38
Author(s):  
M. Abkar ◽  
P. Forooghi ◽  
A. Abbassi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Layer ◽  
Biot Number ◽  
Equilibrium Condition ◽  
Solid Phase ◽  
Local Thermal Equilibrium ◽  
Thermal Conductivity Ratio ◽  
Constant Wall Temperature ◽  
Non Equilibrium

In this paper, forced convection in a channel lined with a porous layer is investigated. The main goal is to assess the effect of local thermal non-equilibrium condition on overall heat transfer in the channel. The effects of thermal conductivity of solid and thickness of porous layer are also studied. Flow assumed to be laminar and fully developed. The Brinkman-Forchheimer model for flow as well as the two equation energy model is used. The results showed that when the problem tends to local thermal equilibrium condition, heat transfer is enhanced due to heat conduction through solid phase. Another factor, which can facilitate the heat transfer, is the increase of the thermal conductivity of solid material. This trend is sensitive to the thickness of porous layer and modified Biot number, which is a measure (criterion) of local fluid to solid heat transfer. As thickness and modified Biot number increase, the Nusselt number becomes more sensitive to the thermal conductivity ratio.

Mixed convection squeezing three-dimensional flow in a rotating channel filled with nanofluid

2016 ◽  
Vol 26 (5) ◽  
pp. 1460-1485 ◽  
Author(s):  
B Mahanthesh ◽  
B J Gireesha ◽  
R S R Gorla
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Differential Equations ◽  
Mixed Convection ◽  
Three Dimensional ◽  
Vertical Channel ◽  
Three Dimensional Flow ◽  
Content Type ◽  
Dimensional Flow ◽  
Rotating Channel

Purpose – The purpose of this paper is to numerically solve the problem of an unsteady squeezing three-dimensional flow and heat transfer of a nanofluid in rotating vertical channel of stretching left plane. The fluid is assumed to be Newtonian, incompressible and electrically conducting embedded with nanoparticles. Effect of internal heat generation/ absorption is also considered in energy equation. Four different types of nanoparticles are considered, namely, copper (Cu), alumina (Al2O3), silver (Ag) and titanium oxide (TiO2) with the base fluid as water. Maxwell-Garnetts and Brinkman models are, respectively, employed to calculate the effective thermal conductivity and viscosity of the nanofluid. Design/methodology/approach – Using suitable similarity transformations, the governing partial differential equations are transformed into set of ordinary differential equations. Resultant equations have been solved numerically using Runge-Kutta-Fehlberg fourth fifth order method for different values of the governing parameters. Effects of pertinent parameters on normal, axial and tangential components of velocity and temperature distributions are presented through graphs and discussed in detail. Further, effects of nanoparticle volume fraction, squeezing parameter, suction/injection parameter and heat source/sink parameter on skin friction and local Nusselt number profiles for different nanoparticles are presented in tables and analyzed. Findings – Squeezing effect enhances the temperature field and consequently reduces the heat transfer rate. Large values of mixed convection parameter showed a significant effect on velocity components. Also, in many heat transfer applications, nanofluids are potentially useful because of their novel properties. They exhibit high-thermal conductivity compared to the base fluids. Further, squeezing and rotation effects are desirable in control the heat transfer. Originality/value – Three-dimensional mixed convection flows over in rotating vertical channel filled with nanofluid are very rare in the literature. Mixed convection squeezing three-dimensional flow in a rotating channel filled with nanofluid is first time investigated.

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