Fluid-saturated Porous Cavity Research Articles

Heat transfer enhancement of mixed convection in an inclined porous cavity using Cu-water nanofluid

In this paper, mixed convection of Cu-nanofluid in an inclined fluid-saturated porous cavity is numerically analyzed by considering three different cases depending on the direction of moving wall(s). The equations of nanofluid-saturated porous medium can be derived by the Darcy-Brinkman-Forchheimer model and are solved using the SIMPLE algorithm. The effect of various non-dimensional parameter such as the Richardson number, Darcy number, inclination angle, solid volume fraction and three different cases are carefully analyzed. The obtained results are presented in the form of streamlines, isotherms, mid-height velocity profiles and average Nusselt number. It is found that the flow and heat transfer play a significant role with the direction of the moving wall(s).

Darcy mixed convection in a fluid saturated square porous enclosure under multiple suction effect

PurposeIt is well known that the mixed convection process is the combined effect of the presence of both the forced and the free convection processes. In several applications such as environmental chambers, IC engines, etc. the forced convection is brought in by multiple suction/injection (S/I) effect. Study of mixed convection in a vertical square fluid saturated porous cavity with multiple S/I effect greatly contributes to such an understanding. So far, not much research work has reported in this direction. Hence, the purpose of this paper is to investigate such a mixed convection process in a fluid saturated vertical porous square cavity.Design/methodology/approachIn this study, the authors numerically solved the couple partial differential equations governing the mixed convection process in a fluid saturated vertical square porous cavity by finite element method. The study is parametric in nature wherein the authors cover a large range of values for different parameters arising the mathematical model governing the problem under consideration.FindingsThe influence of multiple S/I effects on mixed convection is analyzed for a wide range of controlling parameters such as S/I flow velocities (a), S/I window size (D/H) and Rayleigh number (Ra). Both the flow and temperature fields are highly sensitive to magnitude of S/I velocity, S/I window slit size and “Ra”. While heat fluxes along the isothermal left vertical wall decrease with increasing S/I velocities they are formed to increase with increasing “(D/H)” and “Ra”. Nusselt numbers increase with increasing “Ra” and increasing size of S/I window slit size. Multi‐cellular circulation pattern and thermal boundary layers are seen to manifest in flow and temperature fields, respectively.Research limitations/implicationsThe study is based on 2D model, but the model is generic in nature; also it is fully numerical in nature. Due to lack of apt literature no experimental support is provided. The mathematical model used in the study is based on certain assumptions such as isotropic porous medium, fluid is viscous in nature and follows Newtonian laws and the porous structure is saturated with fluid, etc. Regarding future work, 3D modelling and simulation is in progress and attempts are also being made to collaborate with experimental groups on the problem under investigation.Practical implicationsThe results from the work are relevant to the context of heat and fluid flow studies in IC engines, influence of mixed convection process on bacterial growth process in environmental chambers and cooling of electronic devices, etc.Originality/valueThe paper describes a mathematical model, especially the boundary treatment, for describing the influence of multiple S/I effects on mixed convection flow in a vertical square enclosure filled with a Darcian fluid saturated homogeneous porous medium. To understand the physics behind the mixed convection process in the proposed configuration, extensive numerical simulations have been carried out for the first time for different values of the important governing parameters arising from the model.

The effect of conducting bounding plates on the onset of Horton–Rogers–Lapwood convection

We present an analytical and numerical stability analysis of the onset of natural convection in a horizontal fluid-saturated porous cavity. The cavity is bounded by thin horizontal plates with uniform thickness whose outer surfaces are subject to a constant heat flux. The main aim is to determine the effect of the presence of the bounding plates on the onset of convection. The onset criterion is found to be sensitively dependent on the relative thickness of the plates and the porous layer, δ, and their relative conductivities, d. For the long wavelength mode it is precisely Ra c = 12(1 + 2 δd).

Steady-state conjugate natural convection in a fluid-saturated porous cavity

The current numerical investigation addresses the wall heat conduction effect on the natural-convection heat transfer within a two-dimensional cavity, which is filled with a fluid-saturated porous medium. The problem configuration consists of two insulated horizontal walls of finite thickness and two vertical walls which are maintained at constant but different temperatures. The generalized model of the momentum equation, which is also known as the Forchheimer–Brinkman-extended Darcy model, is used in representing the fluid motion inside the porous cavity. The local thermal equilibrium condition is assumed to be valid for the range of the thermophysical parameters considered in the present investigation. The steady-state solution is sought from the undergoing investigation. The momentum and energy transport processes within the porous cavity is examined through depicting the streamlines and isotherms for different domains of a selected dimensionless groups. These dimensionless groups and their respective domains are as follows: W = 0.0075 – 0.2 , K r = 1 – 10 , k s / k f = 0.1 – 100 , Ra = 10 4 – 10 6 , Da = 10 - 5 – 10 - 1 , ε = 0.25 – 0.95 and AR = 0.25 – 2 . The significance of varying these parameters on the predicated average Nusselt number is highlighted and discussed. Finally, the investigation is concluded by presenting the sensitivity of the interface temperature upon varying the above dimensionless groups.

Magnetohydrodynamic free convection and entropy generation in a square porous cavity

The problem of entropy generation in a fluid saturated porous cavity for laminar magnetohydrodynamic natural convection heat transfer is analyzed in this paper. Heat transfer results are also presented additionally. Darcy's law for porous media is considered. Magnetic force is assumed acting along the direction of the gravity force. As boundary conditions of the cavity, two vertical opposite walls are kept at constant but different temperatures and the remaining two walls are kept thermally insulated. For a range of Rayleigh number ( Ra=1–10 4) and Hartmann number ( Ha=0–10), heat transfer, overall entropy generation rate, and heat transfer irreversibility are presented in terms of dimensionless Nusselt number ( Nu), entropy generation number ( Ns), and Bejan number ( Be), respectively. Finally, parametric results are presented in terms of isothermal lines, streamlines, isentropic lines, and iso-Bejan lines.

Analysis of thermal convection in a fluid-saturated porous cavity with internal heat generation

In this paper, the thermal convection flow in a fluid-saturated porous cavity with external sidewall heating and internal heat generation is studied by a semi-implicit projection finite element method. Concerned physical phenomena are constructed by impulsively switching on a uniform internal heat generation at t = 0 in a steady state flow field established by two different sidewall temperatures. Flows in the range 103 ≤ Ra I ≤ 108 and Ra E = 105 are mainly investigated for porous media ɛ = 0.4 and 10–10 < Da < 10–1. The results include the steady state flow field and heat transfer phenomena, as well as the evolution of heat transfer. According to the results, porosity demonstrates obvious influence in heat transfer as Da ≥ 10–2, and permeability significantly affects the flow field and heat transfer rate for Da < 10–2. The decrease in permeability diminishes the strength of external heating driven circulation and provides a chance for the cell driven by internal heat generation to develop. In addition, the flow in a porous medium with smaller flow restriction more quickly reaches the steady state from the instantaneously started internal heat generation.

Double-diffusive natural convection in a fluid saturated porous cavity with a freely convecting wall

Double — diffusive natural convection in fluid saturated porous medium has been investigated using a generalised porous medium model. One of the vertical walls of the porous cavity considered is subjected to convective heat and mass transfer conditions. The results show that the flow, heat and mass transfer become sensitive to applied mass transfer coefficient in both the Darcy and non-Darcy flow regimes. It is also observed that the Sherwood number approaches a constant value as the solutal Biot number increases.

Modelling and simulation of natural convection flow in a saturated porous cavity

Using the continuous theory of mixtures (a generalization of the classical continuum mechanics), a systematic model for a local description of the natural convection flow in a two-dimensional fluid-saturated porous cavity is proposed. It considers the fluid and the porous matrix as continuous constituents of a binary (solid-fluid) mixture, coexisting superposed. The model, simplified by the Boussinesq approximation, is simulated with the help of the control volumes method. The effect of some usual parameters such as Rayleigh, Darcy and Prandtl numbers and of a new dimensionless number, relating coefficients associated with the heat exchange between the fluid and the solid constituents (due to its temperature difference) and coefficients of heat conduction for each constituent, is considered. Qualitative agreement with results using the classical approach (Darcy's law and additional terms to account for boundary and inertia effects, used as momentum equation) was obtained.

Natural convective heat transfer in a rectangular porous cavity with variable fluid properties—validity of the Boussinesq approximation

In this work, the applicability of the Boussinesq approximation is investigated for natural convection in a fluid-saturated porous cavity with vertical walls maintained at two different temperatures and horizontal walls completely insulated. Numerical calculations are performed for two different fluids of practical interest, water and air, in a wide range of Rayleigh numbers and aspect ratios. Flow and temperature fields and heat transfer rates obtained through the evaluation of a model that includes fluid temperature dependent properties, are presented. One of the most important conclusions is that the Nusselt number evaluated through the Boussinesq approximation can be substantially different from the Nusselt number obtained with this model.