Halkasal boşluktaki doğal taşınımlı faz değişiminin sayısal simulasyonu

Natural convection has an important role in the thermal processes, thermal energy storage systems, and phase change problems. Because of this reason, natural convection is an important aspect to be focused and needed to be taken into consideration for efficient system design. The objectives of this thesis the investigation of the natural convection occurred in the cylindrical annulus and the effects of the natural convection on the phase change problem. Within this context, two main problems are investigated. First one is the natural convection inside a cylindrical annulus. A 2D model is established in MATLAB® to observe the natural convection phenomenon for air and water domains. Governing equations are reduced into algebraic sets of equations by using finite volume method. In conclusion, when Prandlt number is at seven for water and temperature differences increases, Nusselt number increases up to four centigrade degrees, then decreses up to approximately nine centigrade degrees then increase again for different ratio of differences of inner and outer radii to inner radii. Numerical results are validated, making use of the available experimental data from the literature. Secondly, phase change inside the cylindrical annulus is investigated for various parameters, i.e., outer wall temperature, the initial temperature of the ice and aspect ratio of the cylindrical annulus. When inner wall temperature is at four, eight and fourteen centigrade degrees for aspect ratio is at two, four and eight, melting times are compared. Then, this observations are done for same temperatures and aspect ratios for outer wall. These numerical results as well are compared with the literature findings a satisfactory agreement is found between the numerical results and experimental literature data. Keywords: Heat transfer, natural convection, cylindrical annulus, mathematical model, phase change