Laminar Free Convection Heat Transfer Research Articles

Numerical Predictions of Laminar Free and Mixed Convection Heat Transfer to Supercritical Water from a Non-Isothermal Vertical Plate

Numerical predictions of heat transfer have been made for laminar free and mixed convective heat transfer from non-isothermal vertical plane surface to supercritical water. Variation of all the thermo-physical properties of the supercritical fluid under investigation have been considered. The numerical scheme employed in the present investigation is first validated with respect to experimental data for isothermal wall conditions and good agreement is achieved with maximum deviation not exceeding 15 %. Linear and parabolic variation of wall temperatures are considered for the present investigation. Computations are made for two pressures of 225 Bar and 235 Bar, for wide range of temperature difference from 4K to 20K. The values of temperature difference are chosen. Based on the results obtained, correlations have been proposed to evaluate the Nusselt numbers for both free and mixed convection with pressure ratios of P/Pc = 1.02 (p = 225 bar) and P/Pc = 1.065 (p = 235 bar). The correlations cover a range of Rayleigh numbers, Rax from 106 to 109 for Free Convection and grashoff Number/Reynolds Number2 ranging from 0.4 to 8 for Mixed convection. The proposed correlations for local Nusselt numbers do not exceed maximum deviation of 15% from the predicted values. It has been found that the maximum deviation occurs for those cases for which the pseudo-critical temperature, T* is within the boundary layer. It is further observed that for these cases both the velocity and temperature profiles are distorted at locations where the temperature is close to the pseudo-critical temperature thereby affecting the gradients at the wall, which in turn influences the heat transfer coefficient.

Numerical investigation on the effects of different heating systems and coil tube arrangements on the free convection heat transfer in a confined space filled with high viscosity fluid

Laminar free convection heat transfer in a confined space filled with high viscosity fluid is numerically investigated for different heating systems and coil tube arrangements at Rayleigh (Ra) numbers in the range of 103 ≤ Ra ≤ 107. In the heating system where the hot coil tubes are immersed in the high viscosity fluid, the effects of the horizontal and vertical distances between the coil tubes and the positions of the coil tubes along the vertical axis on the heat transfer characteristics are studied. The heating system where the coil tubes are placed outside the confined space is also considered. Two-dimensional unsteady conservation equations of the continuity, momentum and energy are discretized and solved by using the finite volume method. The results show that the average Nusselt numbers on all coil tubes except the lower coil tube at Ra = 107 increase as the horizontal and vertical distances between the coil tubes increase. It is found that the horizontally aligned coil tube arrangement is more effective in terms of overall Nusselt number on the coil tube than the vertically aligned coil tube arrangement. The heating system where the coil tubes are outside the confined space at Ra = 107 provides an improvement of 3.25% in average Nusselt values compared to the heating system with horizontally aligned coil tube arrangement. The horizontal distance between the coil tubes, the positions of the coil tubes along the vertical axis and different arrangements of coil tubes have considerable effects on the total Nusselt number. However, the effect of the vertical distance between the coil tubes on the total Nusselt number is negligible at high Ra numbers, 105 ≤ Ra ≤ 107. The numerical method and solution procedure are validated by comparing the results with the available data in the literature.

Laminar free convection from an elliptic tube placed in a Microplar fluid with vertical plate as a special case.(Dept.M)

In this paper laminar free convection heat transfer from a horizontal isothermal elliptic tube placed in a micropolar fluid with its major axis vertical is investigated. The governing equations basd on the conservation of mass, linear momentum, angular momentum and energey are numerically solved using the Fourier Spectral method. The main controlling parameters, beside the material parameters of the micropolar fluid, are the Rayleigh number, the Prandil number and the elliptic section axis ratio The micropolar fluid parameters are the vortex Viscosity, micro-inertia density and Spin gradient viscosity The results, which were obtained for a range of these parameters, were carried Out. at two axis ratios of 0.5 and 0.025. The axis ratio of 0.025 approximates the geometry of the special case of vertical flat plate. The results for vertical plate placed in Newtonian fluid arc compared with the relevant results in the literature and very good agreement was obtained. The study has shown that the vortex viscosity is the frost influencing material parameter on heat transfer rate. The study showed that as the vortex viscosity increases the heat transfer rate decreases.

Numerical Study of Heated Tube Arrays in the Laminar Free Convection Heat Transfer

Laminar free convection heat transfer from a heated cylinder and tube arrays is studied numerically to obtain the local and average Nusselt numbers. To verify the numerical simulations, the Nusselt numbers for a single cylinder were compared to other authors for the Rayleigh numbers of 103 and 104. Furthermore, the vertically arranged heated tube arrays 4 × 1 and 4 × 2 with the tube ratio spacing SV/D = 2 were considered, and obtained average Nusselt numbers were compared to the existing correlating equations. A good agreement of the average Nusselt numbers for the single cylinder and the bottom tube of the 4 × 1 tube array is proved. On the other hand, the bottom tubes of the 4 × 2 tube array affect each other, and the Nusselt numbers have a different course compared to the single cylinder. The temperature fields for the tube array 4 × 4 in basic, concave, and convex configurations are studied, and new correlating equations were determined. The simulations were done for the Rayleigh numbers in the range of 1.3 × 104 to 3.7 × 104 with a tube ratio spacing S/D of 2, 2.5, and 3. On the basis of the results, the average Nusselt numbers increase with the Rayleigh numbers and tube spacing increasing. The average Nusselt number and total heat flux density for the convex configuration increase compared to the base one; on the other hand, the average Nusselt number decreases for the concave one. The results are applicable to the tube heaters constructional design in order to heat the ambient air effectively.

Fluid-structure interaction analysis of buoyancy-driven fluid and heat transfer through an enclosure with a flexible thin partition

PurposeA numerical model of an unsteady laminar free convection flow and heat transfer is studied in a cavity that comprises a vertical flexible thin partition.Design/methodology/approachThe left and right vertical boundaries are isothermal, while the horizontal boundaries are insulated. Moreover, the thin partition, placed in the geometric centerline of the enclosure, is considered to be hyper elastic and diathermal. Galerkin finite-element methods, the system of partial differential equations along with the appropriate boundary conditions are transformed to a weak form through the fluid-structure interaction and solved numerically.FindingsThe heat transfer characteristics of the enclosure with rigid and flexible partitions are compared. The effect of Rayleigh number and Young’s modulus on the maximum nondimensional stress and final deformed shape of the membrane is addressed.Originality/valueIncorporation of vertical thin flexible membrane in middle of a cavity has numerous industrial applications, and it could noticeably affect the heat and mass transfer in the enclosure.

Adiabatic partition effect on natural convection heat transfer inside a square cavity: experimental and numerical studies

A steady state and two-dimensional laminar free convection heat transfer in a partitioned cavity with horizontal adiabatic and isothermal side walls is investigated using both experimental and numerical approaches. The experiments and numerical simulations are carried out using a Mach-Zehnder interferometer and a finite volume code, respectively. A horizontal and adiabatic partition, with angle of θ is adjusted such that it separates the cavity into two identical parts. Effects of this angel as well as Rayleigh number on the heat transfer from the side-heated walls are investigated in this study. The results are performed for the various Rayleigh numbers over the cavity side length, and partition angles ranging from 1.5 × 105 to 4.5 × 105, and 0° to 90°, respectively. The experimental verification of natural convective flow physics has been done by using FLUENT software. For a given adiabatic partition angle, the results show that the average Nusselt number and consequently the heat transfer enhance as the Rayleigh number increases. However, for a given Rayleigh number the maximum and the minimum heat transfer occurs at θ = 45°and θ = 90°, respectively. Two responsible mechanisms for this behavior, namely blockage ratio and partition orientation, are identified. These effects are explained by numerical velocity vectors and experimental temperatures contours. Based on the experimental data, a new correlation that fairly represents the average Nusselt number of the heated walls as functions of Rayleigh number and the angel of θ for the aforementioned ranges of data is proposed.

Natural convection of nanofluids in a cavity: criteria for enhancement of nanofluids

PurposeThe purpose of this study is to theoretically analyze the laminar free convection heat transfer of nanofluids in a square cavity. The sidewalls of the cavity are subject to temperature difference, whereas the bottom and top are insulated. Based on the available experimental results in the literature, two new non-dimensional parameters, namely, the thermal conductivity parameter (Nc) and dynamic viscosity parameter (Nv) are introduced. These parameters indicate the augmentation of the thermal conductivity and dynamic viscosity of the nanofluid by dispersing nanoparticles.Design/methodology/approachThe governing equations are transformed into non-dimensional form using the thermo-physical properties of the base fluid. The obtained governing equations are solved numerically using the finite element method. The results are reported for the general non-dimensional form of the problem as well as case studies in the form of isotherms, streamlines and the graphs of the average Nusselt number. Using the concept of Nc and Nv, some criteria for convective enhancement of nanofluids are proposed. As practical cases, the effect of the size of nanoparticles, the shape of nanoparticles, the type of nanoparticles, the type of base fluids and working temperature on the enhancement of heat transfer are analyzed.FindingsThe results show that the increase of the magnitude of the Rayleigh number increases of the efficiency of using nanofluids. The type of nanoparticles and the type of the base fluid significantly affects the enhancement of using nanofluids. Some practical cases are found, in which utilizing nanoparticles in the base fluid results in deterioration of the heat transfer. The working temperature of the nanofluid is very crucial issue. The increase of the working temperature of the nanofluid decreases the convective heat transfer, which limits the capability of nanofluids in decreasing the size of the thermal systems.Originality/valueIn the present study, a separation line based on two non-dimensional parameters (i.e. Nc and Nv) are introduced. The separation line demonstrates a boundary between augmentation and deterioration of heat transfer by using nanoparticles. Indeed, by utilizing the separation lines, the convective enhancement of using nanofluid with a specified Nc and Nv can be simply estimated.

Laminar free convection heat transfer and separated flow structure in a vertical channel with isothermal walls and two adiabatic opposing fins

Results of numerical study of laminar free convection and heat transfer in a vertical plane-parallel channel with two thin adiabatic fins on its walls are presented. The channel has the open inlet and outlet, and its surfaces are maintained at the same temperature. The channel height is unchanged with elongation parameter A = L/w = 10, and the fins are located in the middle of the channel toward each other. Fin height l/w = 0 ÷ 0.4 and Rayleigh number Ra = 102 ÷ 105 are varied in calculations. The effect of these parameters on the flow structure, temperature field, local and integral heat transfer, and gas flow caused by gravitational forces are analyzed in detail. Numerical analysis is based on solving the full Navier–Stokes and energy equations in twodimensional statement and Boussinesq approximation. To determine the dynamic and thermal parameters at the inlet and outlet, the calculation is carried out with two large volumes attached to the inlet and outlet. The features of the flow and heat transfer at separated flow around the channel fins are studied in detail in this work.

Laminar free convection heat transfer between vertical isothermal plates

The paper represents results on numerical investigation of flow and heat transfer between two isothermal vertical plates under laminar natural convection. A system of complete Navier–Stokes equations is solved for a two-dimensional gas flow between the plates along with additional rectangular regions (connected to inlet and outlet sections), whose characteristic sizes are much greater than the spacing between the plates. The calculations were performed over very wide ranges of Rayleigh number Ra = 10 ÷ 105 and a relative channel length AR = L/w = 1 ÷ 500. The influence of the input parameters on the gas-dynamic and thermal structure of thermogravitational convection, the local and mean heat transfer, and also the gas flow rate between the plates (convective draft. We determined sizes of the regions and regime parameters when the local heat flux on the walls tends to zero due to the gas temperature approach to the surface temperature. It is shown that the mean heat transfer decreases as the relative channel length AR grows, whereas the integral gas flow rate (convective draft) and Reynolds number in the channel Re = 2wUm/ν increase. The use of a modified Rayleigh number Ra* = Ra · (w/L) (Elenbaas number) leads to generalization of calculation data on mean heat transfer. These data are in good agreement with the correlations for heat transfer [1, 2] and gas flow rate [3]. The reasons of variation of the data in the range of low Rayleigh numbers are discussed in detail.

Natural convection of a nanofluid in an enclosure with an inclined local thermal non-equilibrium porous fin considering Buongiorno’s model

ABSTRACTThere is growing interest in application of inclined fins to a cavity wall. As such, this paper focuses on the numerical investigation of laminar free convection flow and heat transfer in an enclosure with an inclined thin local thermal non-equilibrium porous fin and saturated by a nanofluid. The porous medium is assumed to be isotropic and homogenous, the cavity walls are assumed to be impermeable to the nanoparticles, and there is a no-slip boundary condition on the enclosure boundaries. The vertical walls are isothermal and the horizontal ones are adiabatic. Moreover, the influence of indispensable parameters regarding heat and mass transfer, such as Rayleigh number, Darcy number, Prandtl number, porosity, thermophoresis and Brownian parameters, fin length, fin position, and the fin angle on the average Nusselt number, are taken into account. Generally, it is found that the average Nusselt number is an increasing function of Ra, Pr, Da, and porosity (ε). Furthermore, increasing either fin position (Sp) or thermal conductivity ratio (η) produces corresponding decreases in average Nusselt number. Finally, heat transfer shows a different behavior for different values of fin angles and lengths.

Two parameters Lie group analysis and numerical solution of unsteady free convective flow of non-Newtonian fluid

The two-dimensional unsteady laminar free convective heat and mass transfer fluid flow of a non-Newtonian fluid adjacent to a vertical plate has been analyzed numerically. The two parameters Lie group transformation method that transforms the three independent variables into a single variable is used to transform the continuity, the momentum, the energy and the concentration equations into a set of coupled similarity equations. The transformed equations have been solved by the Runge–Kutta–Fehlberg fourth-fifth order numerical method with shooting technique. Numerical calculations were carried out for the various parameters entering into the problem. The dimensionless velocity, temperature and concentration profiles were shown graphically and the skin friction, heat and mass transfer rates were given in tables. It is found that friction factor and heat transfer (mass transfer rate) for methanol are higher (lower) than those of hydrogen and water vapor. Friction factor decreases while heat and mass transfer rate increase as the Prandtl number increases. Friction (heat and mass transfer rate) factor of Newtonian fluid is higher (lower) than the dilatant fluid.

Free Convection in Confined Power-Law Fluids From Two Side-by-Side Cylinders in a Square Enclosure

Laminar free convection heat transfer in power-law fluids from two side-by-side cylinders (one hot and one cold) confined in a square duct has been studied numerically in the two-dimensional flow regime. For a fixed value of the ratio of cylinder radius to size of the enclosure, the effect of geometrical placement of the cylinders is studied on the resulting velocity and temperature fields in the laminar free convection regime by considering six asymmetric locations of the two cylinders. In particular, extensive results reported herein span the range of conditions of Grashof number, 10 to 105; Prandtl number, 0.7 to 100, thereby yielding the range of the Rayleigh number as 7 to 107; power-law index, 0.3 to 1.8; and the relative positions (dimensionless) of the cylinders with respect to the centerline, –0.25 to 0.25. The heat transfer characteristics are analyzed in terms of the local Nusselt number along the surfaces of the two cylinders and the enclosure walls. Overall, the average Nusselt number shows a positive dependence on both the Grashof number and the Prandtl number irrespective of the values of power-law index and relative positioning of the cylinders. Also, all else being equal, shear-thinning fluid behavior promotes heat transfer with reference to that in Newtonian fluids. When the two cylinders are situated close to the bottom wall, the rate of heat transfer is augmented with reference to that for the symmetric positioning of the cylinders along the horizontal mid-plane of the enclosure. Conversely, heat transfer deteriorates as the cylinders are located above the centerline of the enclosure. The present numerical results have been consolidated via the use of a modified Rayleigh number, thereby enabling the estimation of the average Nusselt number in a new application.

A similarity transformation of velocity field and its application for an in-depth study on laminar free convection heat transfer of gases

An innovative similarity transformation of velocity field is reported for equivalent transformation of governing partial differential equations of laminar free convection. To demonstrate its rationality theoretically, its rigorous theoretical derivation is presented firstly in this work. On this basis, an example is presented with successful application for demonstration of its advantages in in-depth study on free convection heat transfer. The governing ordinary differential equations of laminar free convection equivalently transformed by the innovative similarity transformation are presented. It is seen that by the innovative similarity transformation the variable physical properties are transformed into the forms of the related physical property factors, which are organically coupled in the transformed governing ordinary differential equations. It proves that the innovative similarity transformation is very well suitable for consideration of variable physical properties. Then, a new algorithm is presented to calculate fluids flow and heat transfer of laminar free convection. It contains the theoretical and numerical models on laminar free convection, to consider the variable physical properties, to obtain the system of numerical solutions, and then, to create formalization equations for the convection heat transfer coefficient by means of an optimal curve-fitting approach based on the system of numerical solutions. A system of numerical calculations of the governing ordinary differential equations is presented for the gaseous laminar free convection. A temperature parameter model is induced for convenient and reliable treatment of variable physical properties of gases. The delivered formalization equations of heat transfer coefficient on gaseous free convection have strong theoretical and practical value for heat transfer applications because they are created based on the theoretically reasonable similarity transformation model combined with a better model of consideration of fluid's variable physical properties, accurate numerical solutions, and rigorous formalization equations combined with rigorous theoretical derivation. All these prove that the reported innovative similarity transformation is a better alternative applied for in-depth study on free convection heat transfer.

Laminar Free Convection in Bingham Plastic Fluids from an Isothermal Semicircular Cylinder

Laminar free convection heat transfer in Bingham plastic fluids from an isothermal semicircular cylinder has been studied numerically over the following ranges of conditions: Rayleigh number ; Prandtl number and Bingham number . New extensive results on the streamline and isotherm contours adjacent to the semicircular cylinder, yield surfaces separating the fluidlike and solidlike regions, drag coefficient, and local and surface average Nusselt number are discussed in detail, especially with reference to the corresponding behavior observed in ordinary Newtonian fluids. The extent of the unyielded regions progressively increases with Bingham number and/or with the decreasing value of the Rayleigh number. Naturally, conduction dominates heat transfer in the unyielded regions, and convection is relevant only to the yielded regions. In summary, for a given Bingham number, the Nusselt number bears a positive dependence on the Rayleigh number. On the other hand, as the value of the Bingham number is gradually increased, the average Nusselt number decreases from its maximum value in Newtonian media () to its conduction limit () when practically most of the fluid is frozen. Finally, the present numerical values of the average Nusselt number have been consolidated in terms of the modified Rayleigh number and Prandtl number , thereby enabling its prediction in a new application and/or for the intermediate values of the governing parameters.

Laminar Free Convection in Power-Law Fluids from a Heated Hemisphere

Extensive results are presented on the laminar free convection heat transfer in power-law fluids from a heated hemisphere in two orientations, namely, its flat base oriented upward (inverted) or downward (upright). The coupled field equations have been numerically solved over wide ranges of conditions as follows: Grashof number (), Prandtl number () and power-law index (). Detailed flow and temperature fields are visualized in terms of the streamline and isotherm contours, respectively. At the next level, the results are analyzed in terms of the total drag coefficient and local Nusselt number variation along the surface of the hemisphere, together with its surface averaged value. The average Nusselt number increases with both the Grashof and Prandtl numbers. Furthermore, for fixed values of the Grashof and Prandtl numbers, and for a given orientation, shear-thinning behavior () enhances the rate of heat transfer whereas shear-thickening () impedes it with reference to that in Newtonian fluids, especially when there is a reasonable degree of advection. Finally, the present numerical results of drag coefficient and Nusselt number have been correlated using a general composite parameter, which is essentially a modified Rayleigh number. The use of such a Rayleigh number also emphasizes the varying nature of dependence of the average Nusselt number on the Grashof and Prandtl numbers governed by the type of fluid behavior, i.e., shear-thinning () or shear-thickening ().

Free convection from a heated circular cylinder in Bingham plastic fluids

In this work, the equations of motion and energy have been solved numerically using Comsol Multiphysics (version 4.3a) for the laminar free convection heat transfer from a horizontal heated cylinder to Bingham plastic fluids over the range of conditions as: Rayleigh number, 102 ≤ Ra ≤ 106; Prandtl number, 30 ≤ Pr ≤ 100 and Bingham number, 0 ≤ Bn ≤ 104. Extensive results on the streamline and isotherm contours, yielded/unyielded regions, local and average Nusselt numbers are presented and discussed. Owing to the presence of the fluid yield stress, both fluid-like (yielded) and solid-like (unyielded) regions coexist in the flow domain depending upon the prevailing stress levels vis-a-vis the value of the fluid yield stress. Naturally, heat transfer in the solid-like regions occurs purely by conduction and convection is thus restricted to the fluid-like regions. Furthermore, the yielded regions progressively diminish with the increasing value of the Bingham number and/or the decreasing value of the Rayleigh number as the buoyancy-induced flow weakens. All in all, the overall rate of heat transfer is determined by the gradients on the surface of the heated cylinder. Finally, the present numerical values of the average Nusselt number have been correlated in terms of the modified Rayleigh number (Ra∗) and Prandtl number (Pr∗).

Laminar and steady free convection in power-law fluids from a heated spheroidal particle: A numerical study

In this work, the effects of aspect ratio and shear-dependent viscosity on the laminar free convection heat transfer from a heated spheroid immersed in unbounded quiescent power-law fluids have been investigated. In particular, the coupled momentum and energy equations have been solved numerically over the following ranges of the pertinent governing parameters: Grashof number, 10⩽Gr⩽105; Prandtl number, 0.72⩽Pr⩽100; power-law index, 0.3⩽n⩽1.5 and aspect ratio, 0.2⩽e⩽5. Detailed structures of the flow and temperature fields in the vicinity of the spheroid are visualized in terms of the streamline and isotherm patterns, whereas the gross flow and heat transfer phenomena are resolved in terms of the local Nusselt number and its surface averaged value and drag coefficient (CD). Broadly speaking, shear-thinning fluid behaviour (n<1) facilitates heat transfer whereas shear-thickening (n>1) impedes it in comparison to that seen in Newtonian fluids (n=1) under otherwise identical conditions. At fixed values of the Grashof number (Gr), Prandtl number (Pr) and power-law index (n), the value of Nusselt number gradually increases as the spheroid shape progressively passes from the oblate (e>1) to the prolate (e<1) configurations via the spherical shape (e=1). The reverse trend occurs, however, for the drag coefficient (CD). Finally, the present values of the average Nusselt number and drag coefficient are correlated using a simple analytical form based on a general composite parameter proposed for power-law fluids. The paper is concluded by presenting some comparisons with the limited previous analytical and experimental results available in the literature which are limited to Newtonian fluids.

Effect of Orientation on the Steady Laminar Free Convection Heat Transfer in Power-Law Fluids from a Heated Triangular Cylinder

In this work, the influence of orientation on the steady laminar free convection heat transfer from a heated triangular cylinder (flat side facing downward and upward) in quiescent power-law fluids has been investigated. In particular, the coupled momentum and energy equations have been solved numerically over wide ranges of the relevant dimensionless parameters as: Grashof number (10 ≤ Gr ≤ 105), Prandtl number (0.72 ≤ Pr ≤ 100), and power-law index (0.3 ≤ n ≤ 1.8). The detailed flow and temperature fields in the vicinity of the heated cylinder are visualized in terms of the streamline and isotherm contours, respectively. At the next level, the influence of each of the governing parameters, namely, Grashof number (Gr), Prandtl number (Pr), and power-law index (n) on the local and average Nusselt number and drag coefficient, is examined. The flow separation was found to occur at high Grashof numbers and low Prandtl numbers, but only in shear-thickening and Newtonian fluids (n ≥ 1) for the cylinder orientated with its flat side facing upward. Over the range of conditions spanned here, for equal surface area, the rate of heat transfer and drag coefficient are always higher for the cylinder oriented with its flat side facing upward. Broadly speaking, over the range of conditions embraced here, shear-thinning fluid behaviour enhances heat transfer and shear-thickening impedes it. Finally, the present numerical values of the Nusselt number and drag coefficient have been correlated via a simple expression using a composite parameter consistent with the boundary layer analysis. Naturally, this parameter is more effective only at large values of the Grashof and Prandtl numbers, an assumption inherent in the boundary layer approximation.

Numerical study on laminar free convection heat transfer between sphere particle and high pressure water in pseudo-critical zone

Supercritical water fluidized bed reactor (SCWFBR) is a promising new reaction vessel which can effectively gasify wet biomass and efficiently produce hydrogen. Free convection heat transfer from particle in supercritical water (SCW) is a major basic heat transfer mechanism in a fixed bed or fluidized bed with low superficial velocity. In this paper, numerical study on the steady free convection heat transfer around single sphere particle in high pressure water of pseudo-critical zone was carried out. Both the Boussinesq approximation method and real properties model (considering variable specific heat, density, viscosity, and conductivity of SCW) were incorporated to simulate the flow and temperature field. With respect to Boussinesq approximation, real properties model shows higher vorticity and temperature gradients in the vicinity of the sphere surface, which shows variation of thermo-physical property has remarkable effect on the free convection heat transfer process. High local Nusselt number and high heat transfer rate were observed with real properties model.

Optimization of Laminar Free Convection in a Horizontal Cavity Consisting of Flow Diverters Using ICA

The main focus of the present paper is to apply a novel optimization algorithm called as imperialist competitive algorithm (ICA). In this algorithm the cost function being a function of input parameters has to be optimized. In the present research work, our cost function is the laminar free convection heat transfer in a horizontal cavity with adiabatic vertical and isothermally horizontal walls and adiabatic diverters. The input parameters are the diverter angle with respect to horizon varying from 0◦ to 90◦ and Rayleigh number varying from 6 × 103 to 1.2 × 104. After collecting data, the regression equation of averaged convection heat transfer is obtained as a function of the Rayleigh number and diverter angle. Subsequently, the cost function is optimized using the ICA. Results show that the proposed algorithm is powerful enough to be used for optimizing the cost function. According to the results, in order to obtain the maximum heat transfer, the diverter angle must be 27.9◦ whereas; the Rayleigh number must be 1.2 × 104.