Development of a CFD code for computational simulations and flow physics of annular/stratified film condensation flows.

摘要

This thesis provides computational techniques and simulation results for external and internal flows of pure vapor experiencing film condensation on a cooled wall (for any cooling strategy). The primary focus of this dissertation is to provide full computational simulation capability for smooth-interface condensing flows which experience film condensation (with laminar vapor/laminar condensate) on the bottom wall of an inclined (horizontal to vertical) channel. The proposed computational capability is a vital and a necessary step towards successful development of a more comprehensive code capable of handling other important categories of internal condensing flow regimes. For example, suitable modifications of this code can handle wavy-interface turbulent vapor/laminar condensate flows in this geometry. On enhancement of the geometry-handling and interface-tracking aspects of this code, the laminar/laminar flow simulation capabilities can be directly used for simulations relevant to electronic cooling applications involving micro-channels or micro-tubes.; The proposed two dimensional numerical solution scheme for internal and external flows solves the mass, momentum, and energy equations in the interior of each phase, locates the phase change interface, satisfies ail the conditions at the interface, inlet, outlet, and the walls. The proposed scheme has been used to solve some classical smooth-interface external film condensation problems and have found that the resulting numerical solutions are in excellent agreement with classical analytical/numerical solutions.; At a fundamental level, the research results show that conditions at the exit of an internal condensing duct flow, unlike single phase or other noncondensing gas-liquid flows, often significantly influence the flow upstream and are responsible for determining the nature of wavy-interface quasi-steady laminar/laminar flows.; The above capability for smooth interface laminar/laminar flows needs to be extended to simulate wavy-interface turbulent vapor/laminar condensate flows. To facilitate this, a one-dimensional computational solution technique is implemented and important issues of interfacial shear, singularity of the point of onset of condensation, etc. are addressed.