Learn More
In this paper we present an overview of the experimental work carried out as part of research geared towards the understanding of two-phase flow in microchannels. The greater scope of the project is to use the knowledge gained towards the development of strategies to improve water management in fuel cell applications. We have conducted pressure versus flow(More)
In this paper we present a first order study of liquid water detachment and entrainment into air flows in hydrophobic microchannels. A silicon based microfabricated test structure was used for this purpose. It consists of a 500 µm wide by 45 µm deep U-shaped channel 23 mm in length through which air is flown. The structures are treated with a Molecular(More)
Polymer Electrolyte Membrane (PEM) fuel cells incorporating microchannels (D<500 µm) can benefit from improved fuel delivery and convective cooling. However, this requires a better understanding of two-phase microchannel transport phenomena, particularly liquid-gas interactions and liquid clogging in cathode air-delivery channels. This paper develops(More)
Understanding the physics of microscale two-phase flow is important for a broad variety of engineering applications including compact PEM fuel cells and heat exchangers. The low Bond number and confined geometry make it critical to consider both the surface tension at the liquid–gas interfaces and the surface forces acting at the channel boundaries. Within(More)
This paper presents a theoretical model and a numerical simulation of a liquid-gas two-phase flow within a microchannel (50 500 2 m m cm µ µ × ×) equipped with distributed liquid water injection through the side walls. The modeling and solution of the conservation equations provide pressure drop as a function of inlet velocity. The influence of different(More)
Various measurement techniques have been developed recently which provide three-dimensional velocity fields. These methodologies have tremendous potential to improve the understanding of complex flows in both engineering and biomedical applications. Many flows of interest are effectively incompressible which translates into a zero-divergence constraint in(More)
Microchannels (0.05–1 mm) improve gas routing in proton exchange membrane fuel cells, but add to the complexities of water management. This work microfabricates experimental structures with distributed water injection as well as with heating and temperature sensing capabilities to study water formation and transport. The samples feature optical access to(More)
This paper presents experimental data on the effects of varying ambient temperature (10–40 • C) and relative humidity (20–80%) on the operation of a free-breathing fuel cell operated on dry-hydrogen in dead ended mode. We visualize the natural convection plume around the cathode using shadowgraphy, measure the gas diffusion layer (GDL) surface temperature(More)
Industrial trends are presenting major challenges and opportunities for research on two-phase flows in microchannels. Semiconductor companies are developing 3D circuits, for which multilevel microfluidic cooling is important. Gas delivery microchannels are promising for PEM fuel cells in portable electronics. However, data and modeling are needed for flow(More)
This paper presents a theoretical investigation of the movement of liquid droplets and slugs in hydrophobic microchannels and develops a compact model for this type of two-phase flow. This model is used in the prediction of pressure drop and liquid water coverage ratio, key parameters in the operation of Proton Exchange Membrane Fuel Cells (PEMFC), the(More)