Robert S. Wegeng

Microchannel reactors for fuel processing applications. I. Water gas shift reactor

Abstract The water gas shift reactor is one of the critical components of a multi-reactor fuel processing system that supports distributed energy production through the use of a fuel cell. The water gas shift reaction converts carbon monoxide (produced in the primary conversion stage of the fuel processor) and water to carbon dioxide and hydrogen. The water gas shift reaction has slow observed kinetics, with multiple-second contact times, which are cited in fixed-bed reactors. The intrinsic reaction kinetics, however, are measured to be fast, with millisecond contact times, which enables miniaturized deployment in a microchannel reactor. Microchannel reactors reduce heat and mass transport limitations for reactions, and thus facilitate exploiting fast intrinsic reaction kinetics, ie. high effectiveness factors. The implications of this work suggest that a water gas shift reactor for a fuel processor (and other applications) will approach sizes one-to-two orders of magnitude smaller than conventional processing hardware.

Miniaturization technologies applied to energy systems

An overview of the miniaturization technologies and their application to energy systems is presented. Based on the technologies referred to as MEMS (microelectromechanical systems) or MST (micro systems technologies), silicon based micromachining, deep X-ray lithography and the micro mechanical machining processes (micro drilling, milling, cutting, electrical discharge machining, laser, focused ion beams, etc.) will be discussed in the context of application to fluid flow, heat transfer, fluidics and energy systems. An overview of fundamental research and applications will be made with emphasis on the work in the United States. The collaborative work in progress by the Institute for Micromanufacturing and the Pacific Northwest National Laboratories is highlighted. In particular, the on-going development of a micro HVAC (heating, ventilating and air conditioning) system is given specific attention. Devices and/or systems such as micro heat pumps, heat pipes, evaporators, condensers, heat exchangers, compressors and the like will be presented. Advantages, disadvantages and the rationale for miniaturization will be discussed. Current needs and markets will be discussed along with a discussion for future needs.

Compact fuel processors for fuel cell powered automobiles based on microchannel technology

One possible route to the development of compact fuel processing technology is through the application of microchannel technology. Also called micro chemical and thermal systems (micro-cats), microchannel technology is hardware that incorporates engineered microchannels that provide more rapid heat and mass transport, and therefore faster processing rates, than can be realised within systems employing conventional fluid passages. Hardware size is reduced without reducing the processing capacity of the system. Researchers at the US Department of Energys (DOEs) Pacific Northwest National Laboratory (PNNL) are currently developing microchannel heat-exchangers, reactors and separators as components for compact hydrogen generators for fuel cells. This effort, funded by the DOEs Office of Transportation Technology, is now demonstrating high performance in compact units. Over the past year, the project team has concentrated most of its effort on the demonstration of an overall microchannel steam reforming system, including four microchannel steam reformers and more than 24 microchannel heat-exchangers, which as a system are intended to provide both high energy efficiencies and high power densities. Work is also under way on other microchannel components that may ultimately find value within an automotive fuel processing system or within distributed power systems.

Microchannel devices for efficient contacting of liquids in solvent extraction

ABSTRACT Microchannel devices were designed and tested for efficient contacting of two liquids in solvent extraction, and the results are presented. This study is part of an overall effort to produce and demonstrate efficient compact devices for chemical separations. Engineering these devices at the microscale offers many technical advantages. Achieving high contact area per unit system volume, thin-film contacting, and establishing uniform flow distribution result in substantially higher throughput per total system volume over conventional technologies. Theoretical calculations are presented that provide insight into the relative importance of various resistances to mass transfer, as well as their relationship to overall performance of the microchannel devices. Experimental results are presented for device performance using both commercial polymeric membranes and micromachined contactor plates for stabilizing the liquid-liquid interface. These results indicate that current-generation micromachined plates...

Microchannel Chemical Reactors for Fuel Processing Applications. II. Compact Fuel Vaporization

A fuel processor is a critical element for the deployment of automotive fuel cell power systems. One component of the fuel processor, the compact gasoline vaporizer, was demonstrated at full-scale using commercial-grade gasoline. The full-scale process volume was less than 0.3 liters; it vaporized nearly 300 mL/min of gasoline, which is sufficient to support a 50-kWe fuel cell. The reduction in hardware volume was made possible using a microchannel reactor-based design; the compact process hardware is roughly an order of magnitude smaller than conventional technology.

Miniaturization Technologies for Advanced Energy Conversion and Transfer Systems

Microfabricationtechnologieshavemadepossiblethedevelopmentofmeso-scaleenergyconversionandchemical processing systems with microscale features. Scaling effects, such as the linear increase in surface-area-to-volume ratio that affects surface processes such as convection heat transfer, adsorption, and catalytic chemical conversion processes, provide some of the motivation for the miniaturization efforts. Other mechanical, thermal, and e uid scaling effects are presented. Fabrication and material limitations, as well as scaling effects, must be considered in the design process and may result in miniaturized systems that are considerably different than their full-scale prototypes. System and component development efforts at Battelle Pacie c Northwest National Laboratories are highlighted. A fuel atomizer for gas turbine engines and a multicomponent fuel processor for the production of on-demand hydrogen are microscale components that show potential for improving current large-scale systems. Complete miniaturized systems such as a gas turbine, a vapor-absorption heat pump, and a Joule ‐Thompson cryocooler could be used for mobile power production and cooling of electronics and individuals. Components for miniaturized systems include microbatteries with multiple dee nable voltage levels and a high degree of integratability and a combustor/evaporator for methane combustion with low levels of harmful emissions.

Development and Demonstration of a Prototype Solar Methane Reforming System for Thermochemical Energy Storage - Including Preliminary Shakedown Testing Results

12 Infinia Corporation This paper reports on the design, fabrication and preliminary testing of a solar steam- methane reforming system including a parabolic dish solar concentrator, the endothermic chemical reactor and associated heat exchangers. During shakedown testing, methane conversions exceeded 90% and solar-to-chemical energy conversions of about 63 ± 4% were obtained, based on the change in the higher heating value of the stream. Potential applications include thermochemical energy storage for concentrating solar power generation facilities and solar augments of fossil and biomass fuels for power generation and/or synthetic fuel production.

An Extension of Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

The realization of the renewed exploration of the moon presents many technical challenges; among them is the survival of lunar surface assets during periods of darkness when the lunar environment is very cold. Thermal wadis are engineered sources of stored solar energy using modified lunar regolith as a thermal storage mass that can supply energy to protect lightweight robotic rovers or other assets during the lunar night. This paper describes an extension of an earlier analysis of performance of thermal wadis based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. The current analysis has been performed for the lunar equatorial region and validates the formerly used one-dimensional model by comparison of predictions to those obtained from two- and three-dimensional computations. It includes the effects of a thin dust layer covering the surface of the wadi, and incorporating either water as a phasechange material or aluminum stakes as a high thermal conductivity material into the regolith. The calculations indicate that thermal wadis can provide the desired thermal energy and temperature control for the survival of rovers or other equipment during periods of darkness.

Thermal Wadis in Support of Lunar Science & Exploration

Challenges associated with the exploration of the Moon include both the high cost of bringing hardware from Earth (perhaps at costs of

Demonstration of Energy Efficient Steam Reforming in Microchannels for Automotive Fuel Processing

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