Laminar flow fuel cell

Figure 14. Design of an air-breathing laminar flow fuel cell (LFFC) showing the laminar flow profile of the anode side. Adapted with permission from Devin T. Whipple, Ranga S. Jayashree, Daniela Egas, Nicolas Alonso-Vante and Paul J.A. Kenis, Ruthenium cluster-like chalcogenide as a methanol tolerant cathode catalyst in air-breathing laminar flow fuel cells. Electrochi mica Acta 54 (2009) Copyright (2009), with permission from Elsevier.

D ll Power Systems produces direct methanol laminar flow fuel cells mainly for use in laptops although other applications exist... 

Whipple DT, Jayashree RS, Egas D, Alonso-Vante N, Kenis PJA (2009) Ruthenium clusterlike chalcogenide as a methanol tolerant cathode catalyst in air-breathing laminar flow fuel cells. Electrochim Acta 54 4384—4388... 

Microfluidics is a relatively new branch of contemporary physics. It deals with fluid flow and transport phenomena in microstructures with at least one characteristic dimension in the range 1 to 1000 J,m. A microfluidic fuel cell (pFl-FC) (also called a membraneless fuel cell or laminar flow fuel cell) is a type of fuel cell in which all essential functions (i.e., reactant delivery, current-producing electrochemical reaction, and product removal) are conflned to a microfluidic channel. 

A prototype system-integrated microfiuidic fuel cell stack based on the air-breathing direct methanol laminar flow fuel cell technology [42] has been reported by INI Power Systems. A combination of planar and vertical stacking methods was employed to scale the system and increase its power output. With respect to fuel utilization, a fuel and electrolyte separation and recirculation system was proposed at the cost of added complexity and reduced energy density of the complete fuel cell system. 

L. J. Markoski, The laminar flow fuel cell a portable power solution, in 8th Annual International Symposium Small Fuel Cells 2006 Small Fuel Cells for Portable Applications, The Knowledge... 

Hollinger, A.S., Maloney, R.J., Jayashree, R.S., Natarajan, D., Markoski, L.J., and Kenis, P.J.A. (2010) Nanoporous separator and low fuel concentration to minimize crossover in direct methanol laminar flow fuel cells. Journal of Power Sources,... 

L6pez-Montesinos, P.O. et aL (2011) Design, fabrication, and characterization of a planar, silicon-based, monolithically integrated micro laminar flow fuel cell with a bridge-shaped microchaimel cross-section. Journal of Power Sources, 196 (10), 4638-4645. 

One way to ease any difficulties that may arise in fabricating a membrane, especially in design configurations that are not planar, is to go membraneless. Recent reports take advantage of the laminar flow innate to microfluidic reactors ° to develop membraneless fuel cells. The potential of the fuel cell is established at the boundary between parallel (channel) flows of the two fluids customarily compartmentalized in the fuel cell as fuel (anolyte) and oxidant (catholyte). Adapting prior redox fuel cell chemistry using a catholyte of V /V and an anolyte of Ferrigno et al. obtained 35 mA cmr at... 

Many numerical models make additional assumptions, valid if only some specific questions are being asked. For example, if one is not interested in the start-up phase or in changing the operation of a fuel cell, one may apply the steady state condition that time-independent solutions are requested. In certain problems, one may disregard temperature variations, and in the free gas ducts, laminar flow may be imposed. The diffusion in porous media is often approximated by an assumption of isotropy for the gas diffusion or membrane layer, and the coupling to chemical reactions is often simplified or omitted. Water evaporation and condensation, on the other hand, are often a key determinant for the behaviour of a fuel cell and thus have to be modelled at some level. 

An application of microfluidic reactors is the development of a membraneless fuel cell. Two streams, one containing a fuel such as methanol, the other an oxygen-saturated acid or alkaline stream, are merged without mixing. The laminar flow pattern in the narrow channel helps to maintain separate streams without the use of membrane separators. Opposite walls function as the electrodes and are doped with catalyst. Ion exchange, protons for the add system, takes place through the liquid-liquid interface. This is an example of a solid-liquid-liquid-solid multiphase reactor. ... 

Choban, E.R. Markoski, L.J. Wieckowski, A. Kenis, P.J.A. Microfluidic fuel cell based on laminar flow. J. Power Sources 2004, 128, 54-60. 

The focus of this review has been on mass transfer in laminar, single-phase flows. Significant work is necessary for the rigorous analysis of current distribution in turbulent flows. Progress is also required for the analysis of current distribution in multiphase flows, especially in porous media relevant to fuel cell or battery applications. 

Micro fuel cell designs without polymeric membranes can overcome some PEM-related issues such as fuel crossover, anode dry-out or cathode flooding. In these membraneless laminar flow-based fuel cells (LF-EC) two or more liquid streams merge into a single microfluidic channel. The stream flows over the anode and the cathode electrodes placed on opposing side walls within the channel. The reaction of fuel and oxidant takes place at the electrodes while the two liquid streams and their liquid-liquid interface provide the necessary ionic transport [122,123]. 

Finally, it is worth mentioning the microfluidic fuel cells concept [103] introduced by Whitesides in 2002 [104], based in a membraneless fuel cell design which exploit the laminar flowl that occurs in liquids flowing at low Reynolds number to eliminate convective mixing of fuels. Using this concept on-chip, membraneless, air-breathing monolithic pDAFC has been constmcted by Osaka and coworkers [105, 106] which operate with methanol, ethanol and 2-propanol solution containing sulphuric acid or phosphate buffer. The cell consists of two cathodes at the top of the channel, and the hquid fuel is supphed by capillary force to the anode formed on the bottom of the channel, as indicated in Fig. 1.12a, b. 

Ferrigno R, Stroock AD, Clark TD, Mayer M, Whitesides GM (2002) Membraneless vanadium redox fuel cell using laminar flow. J Am Chem Soc 124 12930-12931... 

Laminar flow-based fuel cells Membraneless fuel cells Microfluidic biofuel cells... 

Jayashree RS, Gancs L, Choban ER, Primak A, Natarajan D, Markoski LJ, Kenis PJA (2005) Air-breathing laminar flow-based microfluidic fuel cell. J Am Chem Soc 127 16758-16759... 

These types of three-dimensional electrodes on microchips could also be used for a wider variety of biomethods, including electroporation, drug delivery, and electrostimulated cell culturing. Three-dimensional electrodes will also have applicability in laminar flow-based fuel cells and biofuel cells due to the increase in roughness factor. Three-dimensional electrode... 

R.S. Jayashree, L. Gancs, E.R. Choban, A. Primak, D. Natarajan, L.J. Markoski, P.J.A. Kenis, Air-breathing laminar flow-based microfluidic fuel cell. Journal of the American Chemical Society, 2005, 127, 16758-16759. 

Choban ER, Spendelow JS, Gancs L, Wieckowski A, Kenis PJA (2005) Membraneless laminar flow-based micro fuel cells operating in alkaline, acidic, and acidic/alkaline media. Electrochim Acta 50(27) 5390-5398... 

Mousavi Shaegh, S.A., Nguyen, N.-T., and Chan, S.H. (2011) A review on membraneless laminar flow-based fuel cells. Int.J. Hydrogen Energy, 36 (9), 5675-5694. 

There are substantial differences between GFD modeling of the chemical reactors for fuel processing and that of the fuel cells. Low velocities over the bipolar plates of a fuel cell lead to laminar flow in the channels. As shown in Figure 25.3a, cross flow can be neglected for laminar flow. If fluid mixing between neighboring volume elements is demanded for laminar flow, it must be realized by mixing devices or in... 

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