Three-dimensional Mixed Convection Flow Research Articles

Three-dimensional mixed convection flow of viscoelastic nanofluid over an exponentially stretching surface

Purpose – The purpose of this paper is to investigate the three-dimensional mixed convection flow of viscoelastic nanofluid induced by an exponentially stretching surface. Design/methodology/approach – Similarity transformations are utilized to reduce the partial differential equations into the ordinary differential equations. The corresponding non-linear problems are solved by homotopy analysis method. Findings – The authors found that an increase in thermophoresis and Brownian motion parameter enhance the temperature. Here thermal conductivity of fluid is enhanced due to which higher temperature and thicker thermal boundary layer thickness is obtained. Practical implications – Heat and mass transfer effects in mixed convection flow over a stretching surface have numerous applications in the polymer technology and metallurgy. Such flows are encountered in metallurgical processes which involve the cooling of continuous strips or filaments by drawing them through a quiescent fluid and that in the process of drawing, these strips are sometimes stretched. Originality/value – Three-dimensional flows over an exponentially stretching surface are very rare in the literature. Three-dimensional flow of viscoelastic nanofluid due to an exponentially stretching surface is first time investigated.

Three-dimensional mixed convection squeezing flow

The unsteady mixed convection squeezing flow of an incompressible Newtonian fluid between two vertical parallel planes is discussed. The fluid is electrically conducting. The governing equations are transformed into ordinary differential equations (ODEs) by appropriate transformations. The transformed equations are solved successfully by a modern and powerful technique. The effects of the emerging parameters on the flow and heat transfer characteristics are studied and examined. The values of the skin friction coefficient and the local Nusselt number are tabulated and analyzed.

Three-Dimensional Mixed Convection Flow of Viscoelastic Fluid with Thermal Radiation and Convective Conditions

The objective of present research is to examine the thermal radiation effect in three-dimensional mixed convection flow of viscoelastic fluid. The boundary layer analysis has been discussed for flow by an exponentially stretching surface with convective conditions. The resulting partial differential equations are reduced into a system of nonlinear ordinary differential equations using appropriate transformations. The series solutions are developed through a modern technique known as the homotopy analysis method. The convergent expressions of velocity components and temperature are derived. The solutions obtained are dependent on seven sundry parameters including the viscoelastic parameter, mixed convection parameter, ratio parameter, temperature exponent, Prandtl number, Biot number and radiation parameter. A systematic study is performed to analyze the impacts of these influential parameters on the velocity and temperature, the skin friction coefficients and the local Nusselt number. It is observed that mixed convection parameter in momentum and thermal boundary layers has opposite role. Thermal boundary layer is found to decrease when ratio parameter, Prandtl number and temperature exponent are increased. Local Nusselt number is increasing function of viscoelastic parameter and Biot number. Radiation parameter on the Nusselt number has opposite effects when compared with viscoelastic parameter.

Three-Dimensional Mixed Convection Flow past an Infinite Vertical Plate with Constant Surface Heat Flux

The present paper contains a mathematical analysis of the mixed convection three dimensional steady lami- nar flow of a viscous incompressible fluid past an infinite vertical porous plate. The three-dimensional flow is caused by the transverse sinusoidal suction at the plate. A constant heat flux is prescribed at the plate. Assuming the plate velocity to be uniform, analytical solutions are obtained for the flow field, the temperature field and the skin-friction. Effects of Prandtl number and Grashof number on the flow characteristics are explored and illustrated graphically. In view of the importance of the problems of laminar flow control (LFC), especially in the field of aeronautical engineering, various theoretical and experimental studies of different arrangements and configurations of suction holes and slits have been compiled by Lachmann(1). The suction of the fluid is also an acknowledged technique for control- ling the undesirable features in the boundary layer theory. Further, from the technological point of view, free convec- tion flow and heat transfer problems are always important, for they have many practical applications. The phenomenon of free-convection arises when the difference between the plate temperature and the free stream temperature apprecia- bly large which causes density variations leading to buoyancy forces acting on the fluid elements. This process of heat transfer is encountered in cooling of nuclear reactors, providing heat sinks in turbine blades and aeronautics. Free convection flow past vertical plate has been studied exten- sively by many researchers and some of them are Os- trach(2-3), Stewartson et. al.(4), Sparrow et. al.(5-6), Ma- buchi(7), Riley et. al.(8), Berezovsky et.al.(9), Na(10), Dey et al (11), Kawase et al(12), Martynenko et.al.(13), Weiss et.al.(14) and Pantokratoras(15-16) in numerous ways to include various physical effects. In their work they have restricted themselves to two-dimensional flow only. There may arise situations where the flow fields may be essential- ly three-dimensional, for example when variations in the suction velocity distribution is transverse to the flow direc- tion. Gersten and Gross(17) have studied the effect of such

Modeling of Flow Field and Heat Transfer in a Copper-Base Automotive Radiator Application

This paper describes a methodology used for designing louvered fins. Louvered fins are commonly used in many compact heat exchangers to increase the surface area and initiate new boundary layer growth. Detailed measurements can be accomplished with computational models of these louvered fins to gain a better understanding of the flow field and heat distribution. The particular louver geometry studies for this work have a louver angle of 23° and fin count of 17 fpi. The flow and heat transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with louvered fins are analyzed numerically. A three-dimensional model is developed to investigate flow and conjugate heat transfer in the copper-based car radiator. The model was produced with the commercial program FLUENT. The theoretical model has been developed and validated by comparing the predictions of the model with available experimental data. The thermal performance and temperature distribution for the louvered fins were analyzed and a procedure for optimizing the geometrical design parameter is presented. One fin specification among the various flat tube exchangers is recommended by first considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected radiator are investigated also. The results will be used as fundamental data for tube design by suggesting specifications for car radiator tubes.

Simultaneous Thermal and Mass Diffusion on Three-Dimensional Mixed Convection Flow through a Porous Medium

Simultaneous Thermal and Mass Diffusion on Three-Dimensional Mixed Convection Flow through a Porous Medium

INSTABILITY AND HEAT TRANSFER IN MIXED-CONVECTION FLOW IN A HORIZONTAL DUCT WITH DISCRETE HEAT SOURCES

Three-dimensional mixed-convection flow in a horizontal rectangular duct at low Reynolds numbers has been investigated numerically. Multiple strip heat sources are flush-mounted on the bottom surface, modeling integrated circuit chips on printed circuit boards, and the fluid considered is air. According to the stability diagram presented, four different flow patterns might exist. The discontinuous thermal boundary condition on the bottom makes the longitudinal rolls expand and shrink periodically, and also helps in the generation of transverse rolls. The steady transverse rolls were found even at subcritical Rayleigh numbers for relatively low Reynolds numbers. The implications of these observations to the cooling of electronic equipment are discussed.

FLOW AND HEAT TRANSFER CHARACTERISTICS IN FLAT TUBES OF A RADIATOR

The flow and heat transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with U-shaped grooves are analyzed numerically. The flow and temperature fields are calculated using the developed program that is a modified SIMPLE algorithm for irregular geometry. One tube specification among the various flat tube exchangers is recommended by first considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected tube are investigated also. The results will be used as fundamental data for tube design by suggesting optimal specifications for radiator tubes.

A two-dimensional model of the three dimensional mixed convection flow of Newtonian and non-Newtonian fluids in a rectangular duct

In this study we investigate the three-dimensional (3-D) mixed convection fluid flow within a horizontal duct, the walls of which are assumed to be maintained at specified constant temperatures. The fluid flowing through the duct is assumed to be steady and laminar and the results presented are mainly concentrated on those obtained when using parameter values that are typically found in hydraulic fractures, a technique used in the oil industry to enhance the production rate of an oil well. The full 3-D governing equations are non-dimensionalized and simplified using a narrow gap type approximation and the resulting two-dimensional (2-D) governing equations are found to be parabolic in the streamwise direction. A stream function is introduced into the solution procedure, which consists of marching streamwise along the duct using a finite-difference technique. Results are found for Newtonian and power-law fluids, as well as Newtonian fluids with a temperature dependent viscosity.

MIXED CONVECTION FLOW OF NEWTONIAN AND NON-NEWTONIAN FLUIDS IN A HORIZONTAL RECTANGULAR DUCT

In this study we investigate three-dimensional (3-D) mixed convection fluid flow within a horizontal duct, the walls of which are assumed to be maintained at specified constant temperatures. The flow through the duct is assumed to be steady and laminar, and the results presented are mainly concentrated on those obtained when using parameter values that are typically found in hydraulic fractures, an important process used in the oil industry to enhance the production rate of an oil well. The simplified 3-D governing equations are taken to be parabolic in the streamwise direction, and the solution technique consists of a mixture of finite difference and finite element techniques and an iterative scheme. In order to simulate the fluid flow in ducts that have dimensions similar to a typical fracture, results are obtained for duct heights much greater than duct widths. It is found that in the regions of the duct, that are not in the vicinity of the top and bottom walls the numerical solution asymptotically approaches a 2-D profile. However, simplifying the initial problem to a 2-D model would fail to determine the induced vertical pressure field and the vertical velocity component, both of which are necessary in order to determine whether mixed convection effects influence the settling of proppant in fractures.

Three-dimensional mixed convection flows in a horizontal annulus with a heated rotating inner circular cylinder

The existence of hydrodynamic instabilities leads to the formation of Taylor vortices in flows in the annulus between two concentric cylinders with one or both cylinders rotating. The study of heat transfer within the rotating enclosure is complex. For horizontal configuration, the buoyancy and the centrifugal effects (created by the heated rotating cylinder) are orthogonal and give rise to fully three-dimensional flows. The results of a three-dimensional numerical analysis of flows and heat transfer in a horizontal annulus with a heated rotating inner circular cylinder are presented. Solutions are presented over a wide range of the rotational Reynolds (Taylor) number and the Grashof number. The effect of the centrifugal instability on the heat transfer is examined. The aspect ratio Γ is varied from 1.0 to 10.0 while the radius ratio η for the annulus is maintained at the value of 2.6 for the results presented.

Mixed Convection Heat Transfer to Power Law Fluids in Arbitrary Cross-Sectional Ducts

An analytical investigation of three-dimensional mixed convection flow and heat transfer to power-law fluids in horizontal arbitrary cross-sectional ducts is undertaken. The continuity equation and parabolic forms of the energy and momentum equations in rectangular coordinates are transformed into new orthogonal coordinates with the boundaries of the duct coinciding with the coordinate surfaces. The transformed equations are solved by the finite difference technique. The fluid enters the duct with constant velocity and temperature profiles with the wall of the duct subjected to constant temperature. Local heat transfer coefficients and pressure drop for several values of Gr/Re and power-law index n are computed for the triangular, square, trapezoidal, pentagonal, and circular ducts. The buoyancy force is found to increase both the Nusselt number and the pressure drop.

Unsteady three-dimensional mixed convection flow with temperature dependent viscosity

Effet d'une viscosite dependante de la temperature et du nombre de Prandtl sur la convection mixte laminaire instationnaire incompressible d'eau au point d'arret d'un corps tridimensionnel