Natural convection in rectangular enclosures heated and cooled adjacent walls

SUMMARY Natural Convection in Rectangular Enclosures Heated and Cooled on Adjacent Walls In this study, laminar natural convection in two-dimensional rectangular enclosures is numerically studied. The governing equations obtained through the use of Stream fraction and vorticity formulation and the Boussinesq approximation are solved using finite difference techniques. In the analysis two cases are considered: one concerning steady and the other concerning unsteady natural convection. For the case of steady natural convection, the effects of Rayleigh number, Prandtl number and the aspect ratio of the enclosure on flow pattern and energy transport are investigated in detail for an enclosure heated from one side and cooled from above with other boundaries remaining adiabatic. Computations are carried out for the Rayleigh number range Mf-lO7, Prandtl number range 0.01-100 and aspect ratio range 0.25-4. With the increasing value of Rayleigh number three distinct regimes are described for the flow: Conduction, transition and boundary layer regimes. In order to show convection effects on the flow field, a conduction solution is analytically obtained. A scale analysis is presented for supporting the findings related to the Prandtl number effect.. The effect of enclosure inclination is also investigated by considering various inclination angles between 0° and 360° for an enclosure heated and cooled on adjacent walls. The values of inclination angle at which the maximum and minimum heat transfer rates occur is determined. For the case of unsteady natural convection, an instantaneous temperature change is imposed on one side and the top wall of the enclosure having an initially quiscient fluid with uniform temperature and the development of the flow and temperature fields are investigated. In order test and verify the computer code developed in the present study, different configurations such as a square enclosure having differentially heated vertical walls are also studied and comparison of results obtained with those available in the literature shows a fairly good agreement. Key Words: Enclosure flows, natural convection, steady and transient heat transfer, numerical simulation. VI