On the effects of exothermicity and endothermicity upon the temperature fields in a partially-filled porous channel

Abstract

. (2015) On the effects of exothermicity and endothermicity upon the temperature fields in a partially-filled porous channel. International Journal of Thermal Sciences. Copyright © 2015 ElsevierA copy can be downloaded for personal non-commercial research or study, without prior permission or charge Content must not be changed in any way or reproduced in any format or medium without the formal permission of the copyright holder assumption and, therefore, the validity of the LTE is examined. This is done for a wide range of pertinent parameters including Biot number, conductivity ratio, Darcy number and thickness of the porous insert. It is found that the thermal behaviour of the investigated partially filled system is influenced by the heat sources in both solid and fluid phase. It is further shown that the LTE approach remains an acceptable assumption only for some specific regions of the parametric space. Furthermore, the occurrence of temperature gradient bifurcation on the surface of the porous-fluid interface is examined.It is demonstrated that this effect is highly sensitive to the intensity of the energy sources.

Mixed convection and thermodynamic irreversibilities in MHD nanofluid stagnation-point flows over a cylinder embedded in porous media

“…It is noted that in general the effective viscosity should be used in the governing equations. However, it has been shown previously [7,39,40] that ignoring the effective viscosity does not result in any noticeable error. Further,g, T 1 , e, r nf , B 0 and k 1 denote gravitational acceleration, given temperature at the wall, porosity, nanofluid electrical conductivity, uniform magnetic field and permeability of the porous medium, respectively.…”

“…• The physical mechanisms causing significant deviations from the local thermal equilibrium, such as internal heat generations, are ignored [39,40]. A three-dimensional Darcy-Brinkman model of transport of momentum together with the one-equation model of transport of thermal energy in cylindrical coordinate is used in this work [41][42][43].…”

First and second law analyses of nanofluid forced convection in a partially-filled porous channel – The effects of local thermal non-equilibrium and internal heat sources

“…In particular, this study showed that the internal heat generation in the solid phase has destructive 12 effects upon the second law performance of the system [35]. It is important to note that the general problem of 13 convection in porous media with internal heat sources has recently attracted a considerable attention [37, 38, sources in either of the solid or fluid phase can significantly modify the temperature fields [40] Nusselt number and entropic behaviour of the system [41].…”

“…Forced system with ordinary fluids has been recently analysed by Karimi et al [40]. Similar to the analysis in Ref.…”

“…[40] 5 different porous-fluid interface models [44,45] are employed to define the thermal boundary conditions. The 6 current study builds upon the work of Karimi et al [40] and extends that to nanofluids. Most importantly, this 7 work involves Nusselt number and, local and total entropy generation analyses, which were absent in Ref.…”