This monograph consists of four chapters, each of which present new research in the field of computational fluid dynamics (CFD). Chapter One describes volume of fluid and moving mesh approaches to modeling phase change in a system with particles or droplets in a CFD environment. Chapter Two describes a novel CFD-based design of potential industrial reactors for flash ironmaking. Chapter Three presents a study wherein CFD was used to simulate a hollow fiber membrane contactor for the absorption of carbon dioxide from the air by mono-ethanol amine. Chapter Four describes the use of graphical processor units (GPUs) for the simulation of high-speed and high-temperature flows in CFD.