Simulation of Laminar Natural Convection from Discrete Heat Sources in a Vertical Wall of Square Enclosure


The study represents investigation of the laminar natural convection phenomena in enclosed spaces. Realization of this subject has been done through different Rayleigh numbers, which have to make better understanding and configuration temperature, stream lines and vorticity fields in enclosures. The real physical model of the enclosure, which represents two - dimensional rectangular object with differentially heated sides and adiabatic horizontal walls once and the second case with the adiabatic upper wall only , has been defined in order to predict good enough results. Physical model represents base for mathematical model which defines valid parameters for temperature flow regime. The two dimensional differential conservation equations of mass, momentum and energy are solved by a finite difference method. Air was chosen as a working fluid (Pr=0.7), for Rayleigh number varying from 103 to 105. The changes in temperature and flow fields (stream functions) with increase in Rayleigh number are investigated for different heater locations. The isothermal cold sections adjacent to the heater assist the development of secondary circulation cells, that depend upon both Rayleigh number and the position. With discrete heating and cooling sections on one wall, the flow is characterized by boundary layers lining these sections with separate circulation cells. It is found that Nusselt number is an increasing function of Rayleigh number. The optimum location over the range of Rayleigh number is for the heater mounted at the center of the wall for the first case, and at the low of the wall for the second case. The results were confirmed by previous experiments.