Computational Analysis of Mixed Convection Heat Transfer in a Ventilated Enclosure (original) (raw)

Numerical Simulation on Mixed Convection in a Parallelogrammic Ventilated Enclosure

A parametric numerical investigation is carried out on steady, laminar mixed convection heat transfer in a parallelogrammic ventilated enclosure with a uniform heat source applied on the horizontal bottom wall. Inclined side walls and upper horizontal wall are kept insulated and adiabatic. An external air flow enters the enclosure through an opening located at the bottom of the left vertical wall and exits from an opening located at the top of the opposite wall. The developed mathematical model is governed by the two dimensional continuity, momentum and energy equations. The governing equations, written in non-dimensional form are solved by using Galerkin finite element method. A triangular grid system has been employed for discretization of the computational domain. The Reynolds number is fixed at 100 and the working fluid is considered as air. Parametric studies of the effect of mixed convection parameter, Gr/Re2 (also referred to as Richardson number, Ri), in the range of 0 ~ 10, on the fluid flow and heat transfer are performed for each inclination angle, α of the side walls of the parallelogrammic enclosure. The results are presented in terms of streamlines, isotherms, average Nusselt number and maximum non-dimensional temperature profile. Results show that average Nusselt number increases with the increase of the Richardson number for lower values of positive and negative inclination angle whereas, it remains invariant of Richardson number at higher values of positive and negative inclination angles.

Computation of Flow and Temperature Distribution in Ventilated Enclosure with Uniform Heating of Top Wall

International journal of engineering research and technology, 2014

Combined free convection and forced convection from a uniform heat source on the top wall of a enclosure with inlet and outlet opening is studied numerically. Twodimensional forms of non-dimensional Navier-Stokes equations are solved by using control volume based finite volume technique. Three typical values of the Reynolds numbers are chosen as Re = 1, 10, and 100 and steady, laminar results are obtained in the values of Richardson number as Ri = 0, 1 and 10 and the values of Prandtl numbers as Pr = 0.1, 0.71, 1 and 10. The parametric studies for a wide range of governing parameters show consistent performance of the present numerical approach to obtain as stream functions and temperature profiles. Heat transfer rates at the heated walls are presented based on the value of Re and Pr. The computational results indicate that the heat transfer is strongly affected by Reynolds number and Richardson number. In the present investigation, bottom wall is uniformly heated while the two vertical walls are maintained at constant cold temperature and the top wall is well insulated. A complete study on the effect of Ri shows that the strength of circulation increases with the increase in the value of Ri irrespective of Re and Pr. As the value of Ri increases, there occurs a transition from conduction to convection dominated flow at Ri =1. A detailed analysis of flow pattern shows that the natural or forced convection is based on both the parameters Ri and Pr.

Two Dimensional Numerical Simulation of Mixed Convection in a Rectangular Open Enclosure

A numerical study has been performed on mixed convection inside an open cavity on the bottom of a channel. One of the three walls of the cavity experiences a uniform heat ﬂux while the other walls and the top of the channel are adiabatic. Three different cases are considered by applying uniform heat ﬂux on (a) the inﬂow side (assisting forced ﬂow); (b) the outﬂow side (opposing forced ﬂow); (c) the bottom horizontal surface (transverse ﬂow). The Galerkin weighted residual method of ﬁnite element formulation is used to discretize the governing equations. For mixed convection, the inﬂuential parameters are the Grashof number (Gr), Richardson number (Ri) and Reynolds number (Re) by which different ﬂuid and heat transfer characteristics inside the cavity are obtained. In the present study, velocity vectors, streamlines, isotherms, non-dimensional vertical velocities, maximum non-dimensional heated wall temperature and average Nusselt number of the heated wall are reported for Ri = 0.1 to 100, Re = 100 and the ratio of channel and cavity heights (H/D) with the range of 0.1 to 1.5. With the increase of Richardson numbers, the convective heat transfer becomes predominant over the conduction heat transfer. From the computation, it is observed that the higher heat transfer occurs for opposing forced ﬂow situation at low Richardson number. For higher Richardson number, a better thermal performance is achieved for the transverse ﬂow case.

A Study of Mixed Convection in an Enclosure with Different Inlet and Outlet Configurations

SIJ transactions on computer networks and communication engineering, 2016

A constant flux heat source was heated vertical wall with the fluid considered being air. The other side walls including the top and bottom of the enclosure were assumed to be adiabatic. The inlet opening, located on the left vertical wall, was placed at varying locations. The outlet opening was placed on the opposite heated wall at a fixed location. The basis of the investigation was the two-dimensional numerical solutions of governing equations by using Finite Difference Method (FDM).Significant parameters considered were Richardson number (Ri) and Reynolds number (Re). Results are presented for Richardson number 0 to 10 at Pr=0.71 and Re=50,100,200.The effects of Richardson number and position of the inlet on dimensional temperature inside the enclosure was investigated. The resulting interaction between forced external air stream and buoyancy-driven flow by the heat source are presented in the form of velocity profile and temperature distribution within the enclosure by patterns of graphs. The computational results indicate that heat transfer is strongly affected by Reynolds and Richardson numbers. As the value of Ri increases, there occurs a transition from forced convection to buoyancy dominated flow at Ri>1. A detailed analysis of flow pattern shows that natural or forced convection is based on the parameter Ri.

Mixed Convection Heat Transfer Characteristics in a Channel with an Open Enclosure

Mixed convection heat transfer in an open enclosure, subjected to a flush mounted discrete heat source of constant heat flux partially embedded on the bottom wall while other remaining walls are kept adiabatic, has been investigated numerically. External airflow enters the enclosure through the horizontal channel at a uniform velocity and temperature. Numerical simulation is conducted by using Galerkin residual finite element discretization method. In the present study, the influence of the Richardson number (0 ≤ Ri ≤ 10), the discrete heat source size (0.2 ≤  ≤ 0.8), the inclination angle (0° ≤  ≤ 45°) and the aspect ratio of the cavity ( AR = 0.5, 1, 2) on the thermo-fluid fields has been reported. Disquisitions are presented through the streamlines, isotherms and heat transfer parameters.

Combined Free and Forced Convection Inside a Two-Dimensional Multiple Ventilated Rectangular Enclosure

Combined free convection and forced convection from a flush-mounted uniform heat source on the bottom of a horizontal rectangular enclosure with side openings is studied numerically. The inlet opening allows an externally induced air stream at the ambient temperature to flow through the cavity and exits from another two openings placed top of the both side walls. Two-dimensional forms of Navier-Stokes equations are solved by using control volume based finite element technique. Three typical values of the Reynolds numbers, based on the enclosure height, are chosen as Re = 50, 100 and 200, and steady, laminar results are obtained in the range of Richardson number as 0 ≤ Ri ≤ 10 and a fixed Prandtl number of 0.71. The parametric studies for a wide range of governing parameters show consistent performance of the present numerical approach to obtain as stream functions and temperature profiles. Heat transfer rates at the heated walls are presented in terms of average Nusselt numbers. The computational results indicate that the heat transfer coefficient is strongly affected by Reynolds number and Richardson number. An empirical correlation is developed by using Nusselt number, Reynolds number and Richardson number.

MIXED CONVECTIVE HEAT TRANSFER IN A VERTICAL ENCLOSURE WITH BAFFLE

This paper presents, a numerical study on mixed convective heat transfer of a two dimensional vertical ventilated enclosure with variations of different parameters. All walls are assumed to be adiabatic, but baffle is considered as isothermally heated. Cold air enters the enclosure through an opening from bottom of the left vertical wall and become heated, exits from the top of the right vertical wall. A finite difference method is used for the simulation. The discritized equations with specified boundary conditions are sought by Successive Under Relaxation (SUR) method. It has been done on the basis of stream function and vorticity formulation of the two dimensional Navier-Stokes equation, continuity equation and the temperature distribution at all nodes is calculated by solving energy equation. The investigation carried out with a Reynolds number in the range of 50 ≤ Re ≤ 300, Prandtl number 0.01 ≤ Pr ≤ 2.0 and Richardson number 0 ≤ Ri ≤ 10. The objective of this study is to observed the effect variations of the Richardson number, Prandtl number and Reynolds number for maximum heating efficiency. The maximum heating efficiency is observed at the higher value of Reynolds number and higher value of Richardson number.

Mixed Convective Heat Transfer in an Vertical Enclosure with Baffle

Mixed convection heat transfer in two-dimensional open-ended enclosures

2002

Mixed convection heat transfer in open-ended enclosures has been studied numerically for three different flow angles of attack. Discretization of the governing equations is achieved using a finite element scheme based on the Galerkin method of weighted residuals. Comparisons with previously published work on special cases of the problem are performed and the results show excellent agreement.

Double Diffusive Mixed Convection Heat Transfer inside a Vented Square Cavity

A numerical study has been carried out for laminar double-diffusive mixed convection in a two-dimensional vented square cavity with discrete heat and contaminant sources applied on the bottom wall. An external air ﬂow enters the cavity through an opening located at the bottom of the left vertical wall and exits from an opening located at the three different positions of the opposite wall. The developed mathematical model is governed by the two-dimensional continuity, momentum, energy, and concentration equations. The governing equations, written in non-dimensional form are solved by using Galerkin ﬁnite element method with triangular grid discretization system. The Reynolds number is ﬁxed at 100 and the working ﬂuid is considered as air. Numerical simulations are carried out for different combinations of the thermal Grashof numbers and results are presented in terms of streamlines, temperature and concentration distributions. The results indicate that the average Nusselt and Sherwood numbers on the heat and contaminant sources strongly depend on the positioning of the exit opening.

Computational Analysis of Mixed Convection Heat Transfer in a Ventilated Enclosure (original) (raw)

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