Flows And Heat Transfer In An Air-filled Triangular Cavity

Attic is a room lower of a roof, common with a triangular section. Because of the advantages of insulation and versatility, attic has a lot of functions in buildings. Many researchers have investigated flow characteristics under different boundary conditions. Superior attic may provide a comfortable temperature and achieve the purpose of energy conservation. Flows and heat transfer in a triangular cavity become a focus in recent years because the energy conservation has become one of the national long-term development goals.In the thesis, we use scaling analysis and numerical simulation to analysis natural convection in an isosceles triangle which has a sudden cooling of the top and a suddenly heating of bottom wall. The development of the intrusion and the plume near the horizontal bottom wall has been argued using scaling analysis. We can divided the intrusion into six dominances, namely:unsteady conduction-viscous dominance; unsteady conduction-inertial dominance; unsteady convection-inertial dominance; steady convection-inertial dominance; steady conduction-inertial dominance; steady conduction-viscous dominance. Obtain the scaling relations of the intrusion and the plume under different dominances. In addition, the velocity and thickness scales of the intrusion and the plume have been verified.The feature of the flow in the triangular cavity has been described and the development of natural convection flows in the cavity is classified into three stages:an initial stage, a transitional stage and a fully developed stage, which are dependent on the Rayleigh number and aspect ratio. Additionally, the asymmetrical flow in the cavity is characterized. Further, heat and mass transfer in the cavity is analyzed, and the dependence of the average flow rate and the Nusselt number on the Rayleigh number and aspect ratio is quantified. Further, heat transfer law for high Rayleigh numbers calculated using turbulence model is obtained.The research work includes the scaling analysis of the intrusion and the plume in the triangular cavity and validations. Additionally, flows and heat and mass transfer are described and quantified in the thesis.