P.M. Diéguez

Computational Fluid Dynamics as a Tool for Designing Hydrogen Energy Technologies

This chapter provides an overview of the application of computational fluid dynamics (CFD) to the analysis and design of hydrogen technologies. After presenting the CFD fundamentals the use of this tool to investigate relevant hydrogen production technologies is considered. These technologies are categorized into reactors for the reforming of gaseous fuels (fixed- and fluidized-bed reactors and catalytic wall microreactors) and reactors for the gasification and fast pyrolysis of biomass. Subsequently, the application of CFD for studying fuel cells (polymer electrolyte membrane and solid oxide fuel cells) and hydrogen-fueled internal combustion engines is discussed. It is shown that CFD is a very useful tool for advancing in the development and optimization of these technologies. The interest of CFD for assisting in the understanding of the behavior of hydrogen technologies is also important. Nevertheless there are also limitations regarding the description of chemical transformations and the physics of some complex phenomena such as in multiphasic systems. An effort is required in the coming years to expand the range of applications of CFD in the hydrogen energy field and also for improving the existing models and commercial codes.

Real Time Diagnosis Charts of Thread Quality in Tapping Operations

Tapping by cutting is one of the most common operations in manufacturing. It consists of cutting internal threads on the wall of a previously drilled hole by means of a tool called a tap that has cutting edges on its chamfered periphery. When tap wear is slight the process and geometry are usually in control and correct, respectively. However, when tap wear level is high the geometry is not correct and the process is out of control. This is an unacceptable industrial cost. The aim of this paper consists on an industrial monitoring application to data coming from the current/torque signal of the tap spindle for assessing thread quality. It operates in real time and indicates when the tap wear is so critical that, if the process were continued, it would result in unacceptable screw threads. Then the system shows a red light so that the operator could replace the worn-out tap. The system would be very cost-effective since the tapping process could be run without any operator intervention.

Hydrogen Hazards and Risks Analysis through CFD Simulations

Safety is a key issue for the development and commercialization of hydrogen technologies. This chapter provides an overview of several aspects relevant to the hydrogen safety field. First, the most important international programs that have been undertaken to improve the current understanding of the hazards and risks associated with the hydrogen energy are briefly presented. It is shown this way that hydrogen safety is a very active area of research, development and international collaboration. Next, the main hazards associated to hydrogen are described according to their physiological, physical and chemical effects. The conclusion is that the hydrogen hazards are not greater than those of natural gas or gasoline. Finally, the use of computational fluid dynamics (CFD) for simulating phenomena such as buoyancy, diffusion, deflagration and explosion is considered. Emphasis is put on the modeling of these phenomena and on showing examples of application of CFD to safety-relevant issues such as hydrogen leakages, hydrogen flames, detonation and application of the simulation results to evaluate possible physiological injuries. Despite the successful use of CFD, it is necessary to continue gaining theoretical and experimental information to fill the existing knowledge gaps.