Myron A. Hoffman

Catalytic burner for an indirect methanol fuel cell vehicle fuel processor

Abstract Major impediments to the wide-scale implementation of hydrogen/air fuel cell vehicles are the lack of hydrogen infrastructure and on-board hydrogen storage. One proposed source of hydrogen exists in the development of on-board methanol (and other hydrocarbon) fuel processors. Packaging limitations and fuel processor performance constraints on efficiency and transient response play key roles in vehicular applications. These constraints may be addressed by considering proper thermal integration between two major components of the fuel processor: the reformer and catalytic burner. The focus of this research is on the effects of the catalytic burner on reformer performance in a thermally well-integrated configuration. Specifically, the work has focused on the generation of a detailed numerical model incorporating kinetics and mass and heat transfer to accurately characterize the burner. Unlike a simple, thermodynamic model, the detailed model provides a level of complexity necessary to understand the impact of thermal integration on reformer transient response, reformate composition, and emissions.

The Heat Transport System and Plant Design for the HYLIFE-II Fusion Reactor

HYLIFE is the name given to a family of self-healing liquid-wall reactor concepts for inertial confinement fusion. This HYLIFE-II concept employs the molten salt, Flibe, for the liquid jets instead of liquid lithium used in the original HYLIFE-I study. A preliminary conceptual design study of the heat transport system and the balance of plant of the HYLIFE-II fusion power plant is described in this paper with special emphasis on a scoping study to determine the best intermediate heat exchanger geometry and flow conditions for minimum cost of electricity. 11 refs., 8 figs.

Requirements for low-cost electricity and hydrogen fuel production from multiunit inertial fusion energy plants with a shared driver and target factory

UCRL-JC-115787 Rev 1 PREPRINT Requirements for Low Cost Electricity and Hydrogen Fuel Production from Multi-Unit Inertial Fusion Energy Plants with a Shared Driver and Target Factory G. Logan R. Moir M. Hoffman This paper was prepared for submittal to Fusion Techology December6, 1994 Thisisa preprintof a paper intended for publication a journalor pro~e in edings.Since changes be made may before publication, this preprint is made available with the understanding it will not be cited or reproduced that withoutthe permission the of author.

Inertial fusion energy power plant design using the Compact Torus Accelerator: HYLIFE-CT

The Compact Torus Accelerator (CTA), under development at Lawrence Livermore National Laboratory, offers the promise of a low-cost, high-efficiency, high energy, high-power-density driver for ICF and MICF (Magnetically Insulated ICF) type fusion systems. A CTA with 100 MJ driver capacitor bank energy is predicted to deliver {approximately}30 MJ CT kinetic energy to a 1 cm{sup 2} target in several nanoseconds for a power density of {approximately}10{sup 16} watts/cm{sup 2}. The estimated cost of delivered energy is {approximately}3

Modeling of convective subcooled boiling in microtubes for high heat fluxes

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Heat flux capabilities of first-wall tube arrays for an experimental fusion reactor

100M for 30 MJ. This driver appears to be cost-effective and, in this regard, is virtually alone among IFE drivers. We discuss indirect-drive ICF with a DT fusion energy gain Q = 70 for a total yield of 2 GJ. The CT can be guided to the target inside a several-meter-long disposable cone made of frozen Li{sub 2}BeF{sub 4}, the same material as the coolant. We have designed a power plant including CT injection, target emplacement, containment, energy recovery, and tritium breeding. The cost of electricity is predicted to be 4.8 {cents}/kWh, which is competitive with future coal and nuclear costs.

Heat flux limitations for water-cooled extraction grids in ion accelerators☆

Cooling systems for very compact electronic components and computer chips are being miniaturized to meet the need for smaller overall packaging. One of the important present directions has been to use laminar flow in very small channels with hydraulic diameters in the sub-millimeter range to get high heat transfer coefficients with low pressure drops. It has been speculated that there might be some advantage to having convective subcooled boiling (SCB) occur in the micro-channels. As a first step in the evaluation of the utility of subcooled boiling in these micro-channels, a model has been developed for subcooled boiling in sub-millimeter diameter microtubes subject to uniform heat flux. This model builds on a previously well-validated computer code for convective subcooled boiling in tubes down to 1.57 mm inner diameter. The basic features of the new microtube model are described and some predictions using this model for 0.3 mm and 0.1 mm microtubes subject to a high heat flux of 10 MW/m2 are given.

Clarifying the Butler–Volmer equation and related approximations for calculating activation losses in solid oxide fuel cell models

Abstract A preliminary design study has been made of some of the thermomechanical problems of water and helium cooling for the first wall of a near-term experimental fusion reactor. The first wall is envisioned as an array of 316 stainless steel tubes between the plasma and the blanket modules to intercept a heat flux from the plasma estimated to be between 0.25 and 1.0 MW/m 2 . Evaluations have been made of the maximum allowable heat fluxes for constraints imposed on the tube wall temperature, the cyclic stresses, the quasi-steady stresses and energy recovery from the coolant. For tubes with 2 meter long heated sections, 10 mm inside diameter and 1 mm wall thickness, water cooling was found to be more than adequate for plasma heat fluxes over 1 MW/m 2 with a fatigue life of 10 6 cycles; for a 2 mm wall thickness, at least 0.7 MW/m 2 can be handled for the same fatigue life. Helium-cooled tubes can also handle heat fluxes up to about 1 MW/m 2 with a 1 mm tube wall thickness and over 0.5 MW/m 2 with a 2 mm tube wall thickness, but the required pumping powers tend to be high. The problems of plasma disruptions and erosion by energetic plasma ions are also discussed briefly.

A Comparison of High-Pressure and Low-Pressure Operation of PEM Fuel Cell Systems

Abstract The maximum heat flux which can be handled by water-cooled grid tubes is evaluated for different design and heat transfer constraints. The maximum allowable heat flux is usually found to be limited by the allowable thermal deformations of the grids for nonuniform heating around the circumference of the tube. Detailed results for a grid geometry specifically designed to give very small thermal deformations are presented.