ANALYSIS OF LAMINAR FORCED CONVECTION INSIDE A SQUARE VENTILATED CAVITY USING THE OPENFOAM®

Laminar forced convection inside a square cavity with inlet and outlet ports was numerically analyzed. The positions of the inlet and outlet ports were fixed and the ports sizes were equal 25% of the side wall. The influence of the Reynolds and Prandtl numbers on the flow and temperature fields inside the cavity was verified for nine cases, with Re = 50, 100 and 500 and Pr = 0.7, 3 and 5. The heat transfer process in the cavity was analyzed from obtained values for the average Nusselt number and the local Nusselt number on the walls. The open source computer package OpenFOAM® was used for simulations considering a two-dimensional flow. For all tested Prandtl numbers, there is a growth in the rotating vortex regions as Reynolds number is increases. The temperature fields are directly related to the presence of the rotating vortices and the temperature gradient is more noticeable at the interface sections of the throughflow stream with the neighboring vortices and the next to the walls for greater Reynolds and Prandtl numbers. It was verified that the local Nusselt number on the walls varies radically with minimum and maximum points and it is dependent on the flow and temperature fields adjacent to the respective wall. The results for average Nusselt number per wall indicated that the bottom wall is the most susceptible to variations in its average Nusselt number and that the top wall present higher values of this parameter for all tested cases. Finally, the average Nusselt number was increased with increasing the Reynolds and Prandtl numbers indicating the enhanced thermal exchange

DIMENSIONLESS PHYSICAL-MATHEMATICAL MODELING OF TURBULENT NATURAL CONVECTION

Natural convection heat transfer is present in the most diverse applications of Thermal Engineering, such as in electronic equipment, transmission lines, cooling coils, biological systems, etc. The correct physical-mathematical modeling of this phenomenon is crucial in the applied understanding of its fundamentals and the design of thermal systems and related technologies. Dimensionless analyses can be applied in the study of flows to reduce geometric and experimental dependence and facilitate the modeling process and understanding of the main influence physical parameters; besides being used in creating models and prototypes. This work presents a methodology for dimensionless physical-mathematical modeling of natural convection turbulent flows over isothermal plates, located in an “infinite” open environment. A consolidated dimensionless physical-mathematical model was defined for the studied problem situation. The physical influence of the dimensionless numbers of Grashof, Prandtl, and Turbulent Prandtl was demonstrated. The use of the Theory of Dimensional Analysis and Similarity and its application as a tool and numerical device in the process of building and simplifying CFD simulations were discussed

EXPERIMENTAL METHODOLOGY FOR THE STUDY OF NATURAL CONVECTION ON FLAT AND CORRUGATED PLATES

Natural convection is present in the most different Thermal Engineering systems, such as solar collectors, electric furnaces, electronic equipment cooling, lubrication, thermal comfort projects in buildings, etc. In the last decade, the number of research on natural convection heat transfer has increased considerably, especially in the areas of physical-numerical modeling and validation, experimental construction and efficiency optimization of thermal systems, and related technologies. This work presents an experimental methodology for studying natural convection on flat and corrugated plates. The design and construction stages of the experimental apparatus, data processing and analysis, physical-mathematical modeling and uncertainty analysis were extensively explored. The applications and extensions of the proposed methodology were discussed in the numerical-experimental validation of physical-numerical modeling methodologies, design and optimization of the experimental apparatus and also of measuring instruments and, finally, in sensitivity analysis studies to reduce the propagation of uncertainties. The limitations of the proposed methodology were discussed, pointing out suggestions for future work