Modeling and analysis of flow and heat transfer in a large PEM fuel cell suitable for automotive applications

Official URL: http://risc01.sabanciuniv.edu/record=b1620285 (Table of Contents)

Based on the Zero Emission Vehicle (ZEV) targets, automotive manufacturers realize the necessities to develop new technologies that replace the Internal Combustion Engine (ICE). Nowadays there are two major trends in the automotive industry; First, hybrid vehicles which combine hydrogen energy with combustion energy, and second there is a down-sizing trend. By using hybrid technologies auto makers can obtain a significant drop in emission levels and the efficiencies increase up to 80%. Reaching 80% efficiency is not only achieved by using hybrid technologies. Automotive manufacturers also use different technologies such as the second mega trend: down-sizing. Engine volumes start to decrease but the horse powers of the engines keep increasing. 20 years ago a 2.0lt engine could create up to 120hp. However today, Original Equipment Manufacturers (OEM) could build an engine which can generate 150hp with a1.0lt engine volume. These are great results, but still this technology needs fuel to consume and by using ICE it is not possible to obtain ZEV. In long term this raw material requirement can cause rise in fuel costs. On the other hand, there is still ICE which means there is emission. Fuel cells (FC) can be the shining star of ZEV targets. There are several types of fuel cells that can be applicable to transportation. The most convenient type is Proton Exchange Membrane (PEM) fuel cell due to its start up time, cold performance and working temperature. PEMFC systems can be a great displacement for internal combustion engines in transportation industry [84]. FC technologies have high efficiency and when they used in automotive industry they can reduce the COx emissions. This makes them a potential candidates for European auto companies to meet their voluntary carbon dioxide emission limits in the European Union. The objective of this work is to find a way to decrease the cost of the fuel cells. Time is necessary to obtain deep knowledge on design principles of proton exchange membrane fuel cell (PEMFC) which could be used in automotive applications. Fuel cells are continuous clean energy converters which run on hydrogen or conventional hydrocarbons. They produce energy much more efficiently and they process quieter than ICE systems with higher power densities. For improved design and control of FCs, better understanding of fuel cell systems and components by means of developing and simulating accurate model FC is necessary. In this thesis; combinations of simulations were carried out and the results analyzed for enhancing the understanding of distribution of flow and temperature for a 400 cm2 flow field PEMFC. A three-dimensional (3D) computational fluid dynamics (CFD) based model was used to predict heat and mass distributions of this design. The effect of flow direction and the cooling pattern on this design were also taken into account to enhance the understanding for this selected flow field design.