Numerical Study Of Natural Convection In An Enclosed Cavity

Examples of natural convection can be seen everywhere in life. Knowing and studying the basic characteristics of natural convection have a guiding significance for controlling the building indoor temperature, strengthening and weakening energy. The influence of physical parameters processing method on natural convection numerical results is studied using the theory of fluid mechanics and heat transfer. The natural convection of the different space position, horizontal body force, and temperature distribution is studied using numerical method.First of all, the method of theory and numerical is used to research the natural convective heat transfer of 3d cavity, and the numerical calculation of the average nusselt number is compared with the benchmark solution, the errors are within 0.85% and the correctness of the model and calculation method are verified. Different methods of Physical Properties are applied to conclude that the results of calculation as following. When temperature difference is 500K, the error is as high as 9.54% and 4.82% when fluid density and coefficient of thermal conductivity are seen as constant physical property. In order to guarantee the accuracy of the calculation results, at large temperature difference in the natural convection in the numerical calculation, the influence of the change of fluid density, thermal conductivity coefficient with temperature change on the calculation results should be considered; The heat capacity and dynamic viscosity are calculated as physical properties, the error is relatively small. When temperature difference is 500K, the maximum error is 2.17% and 0.39%.Due to the calculation error is increased with temperature increasing, when the temperature difference is larger than 500K,specific heat, impact on the calculation of dynamic viscosity with temperature changes should also be considered.Secondly, natural convection problem of closed cavity under horizontal volume force is studied, it is concluded that convection strength increases along with the level of positive direction volume force, and weakens with the increase of horizontal negative direction volume force. Under the influence of inclination angle, the stress state of air in closed cavity changes, and causes that natural convection strength increases with negative tilt angle decreases, convection strength becomes decreasing from increasing gradually with positive tilt angle increasing.Again, the air convection condition of square cavity of different temperature distribution at high temperature wall is studied. It is concluded that the influence of the temperature distribution on convection strength is existed, and the method of strengthening and weakening natural convection constant by changing the boundary temperature distribution at constant temperature difference.