Here is a recap what we have learned in this course. When a body immersed in a static fluid is at a different temperature than the fluid, it starts heating or cooling the surrounding fluid. This causes local density variations in the fluid, which is then moved by the buoyant force. This phenomenon is called natural (or free) convection, where the buoyancy drives the heat transfer.
In this course, we explored different types and applications of natural convection. We introduced the governing equations of free convection and discussed the Boussinesq approximation to buoyancy force effects. We analyzed the characteristics of laminar boundary layers generated by natural convection on a vertical surface and the associated heat transfer. Another important concept we studied was external natural convection. Using canonical shapes such as flat plates, cylinders and spheres, we learned about the free-convection-driven motion of fluid around these shapes and how this affects the overall heat transfer. Also, we presented correlations that could be used to estimate the heat transfer for each case. Next, we studied the physics of natural convection heat transfer between parallel plates. We found that the heat transfer in channel arrays can be maximized by optimizing the number of parallel plates and their spacing to balance the effect of available surface area and fluid viscosity. Finally, we discussed natural convection in enclosures where the fluid flow is bounded in a confined space. We analyzed the fluid patterns for canonical cases such as rectangular cavities, concentric cylinders and spheres. We also highlighted useful correlations that can be used to estimate heat transfer in such cases.