Philip S. Schmidt

AN INTEGRAL MODEL FOR DRYING OF HYGROSCOPIC AND NONHYGROSCOPIC MATERIALS WITH DIELECTRIC HEATING

ABSTRACT Heat and mass transport phenomena in drying assisted by microwave or radio-frequency dielectric heating are analyzed. When drying at temperatures near boiling point or with high temperature gradients, the effect of the gas phase pressure gradient on moisture transfer within the solid can be important. The governing heat and mass transfer equations, including consideration of internal heat generation and the effect of the gas phase pressure gradient, are derived and solved in a one-dimensional system using an integral method. The integral model has been used to simulate dielectrically-enhanced convective drying of beds of polymer pellets, glass beads and alumina spheres with flow over the bed surface. Model predictions of drying rates and temperatures agree well with experimental data for these cases. The model provides a relatively fast and efficient way to simulate drying behavior with dielectric heating, and may be useful in design and optimization of dielectrically-enhanced convective drying p...

VOC Recovery through Microwave Regeneration of Adsorbents: Process Design Studies

Process design studies are described for a new type of VOC recovery system which uses microwave heating to regenerate adsorbents. Microwave regeneration systems create a highly concentrated effluent from which the VOCs can be recovered by condensation at near-ambient temperatures. Important design considerations, predicated on experimental work and model development, are identified and discussed. Parametric studies are then described that identify the optimal adsorbent selection, operating cycle, recovery configuration, regeneration pressure, regeneration final coverage, and column configuration. In general, it was found that microwave regenerated adsorption systems favor the use of low dielectric loss-factor polymeric adsorbents and operation under low pressure conditions (about 5 torr absolute pressure).

Can different energy resources be added or compared

The practice of directly adding and comparing Btus of energy from different energy resources may yield misleading conclusions in economic and policy studies. Economic aggregation indices (e.g., Divisia indices) are preferable to a heat-content index. Under some circumstances, an energy aggregate may fail to exist. We review the conditions necessary for aggregation or comparison, contrast different approaches, describe the form-value attributes that affect the relative economic values of different energy resources, and derive the microeconomic foundations of the Divisia approach. The development of an energy-technology Divisia aggregate is suggested when separability between energy and other inputs is not present.

VOC Recovery through Microwave Regeneration of Adsorbents: Comparative Economic Feasibility Studies

Microwave regeneration of adsorbents facilitates the recovery of volatile organic compounds (VOCs) by decoupling the bed heating from the stripping gas. This makes possible the creation of a highly-concentrated regeneration effluent from which the VOCs can be recovered by condensation at near-ambient temperatures. The economic feasibility of two novel microwave-regenerated adsorption systems was evaluated by systematically comparing the capital and operating costs of the proposed systems with 10 conventional VOC control technologies. The microwave systems were found to have similar capital and operating costs to conventional steam regeneration systems and, therefore, may present an attractive alternative for recovering water-miscible solvents. In general, the cost of the microwave subsystem is a relatively small component of the overall system costs, and the microwave power requirements are within the range of commercially available generators, even for large emission streams.

Electricity and industrial productivity: A technical and economic perspective

Factors favoring the use of electricity as an energy source for production are considered and the economic implications of these factors are discussed. Several examples are presented illustrating particular aspects of the electricity-productivity relationship, including arc-furnace steel making, induction heating for forging, and microwave drying in the pasta industry. Other electrotechnologies that may significantly influence overall productivity in industry are cited.

Microwave-Enhanced Regeneration of Adsorbents

An experimental investigation was carried out to determine the regeneration characteristics of adsorbent beds using microwave heating. Tests were performed with water on F-200 activated alumina and on types 4A and 13X zeolite molecular sieves and with methanol on 4A and 13X zeolites. For these systems, microwave heating produced very high rates of regeneration with either gas purge or vacuum purge. Dielectric properties of both the adsorbent and the adsorbate affect the heating response. Temperature profiles in the adsorbent bed show that microwave heating eliminates the mass transfer front characteristic of conventional regeneration. This may have potential implications for improved bed life. The ultimate goal of the program is the recovery of volatile organic compounds (VOCs) by regenerating adsorbents with little or no dilution in a stripping medium.

Managing a major curriculum reform effort in a large research university

This paper describes a substantive undergraduate curriculum reform effort being undertaken over a five year period at the University of Texas at Austin, with special consideration to the management issues that are being addressed. The initiative, called Project PROCEED (for Project-Centered Education), grew out of a desire to strengthen our student’s understanding of fundamental engineering theory by continuously tying it to tangible objects and systems, to strengthen our Department’s connections with its industrial stakeholders by actively involving them in the development and delivery of curriculum content, and to provide our students with a broad range of team-based experiences which will better prepare them for growth and leadership in the corporate and professional world. The rationale for PROCEED and key program elements are described. Management issues, such as logistics, promoting faculty and student buy-in, financing, industrial interaction, and program evaluation are discussed.Copyright

Demand-side management implications of electrically-based manufacturing technologies

The energy consequences of 17 industrial electrotechnologies are considered in the context of 14 2-digit SIC (Standard Industrial Classification) industries as a basis for utility demand-side management decision making. A matrix of electrotechnology-industry application combinations is presented in which each entry falls into one of four categories: 1.(i) increased electricity and primary fuel use, but with positive impact on other production factors,2.(ii) decreased electricity use with negligible end-use fossil fuel impact,3.(iii) increased electricity use but reduced primary fuel use, and4.(iv) decreased electricity and primary fuel use. Examples are presented and energy impacts calculated for several cases to illustrate the tradeoffs involved in electrotechnology process substitution. The implications of these tradeoffs in terms of utility demand-side management program strategies are discussed.

Automated Outcomes-Based Assessment Process for Traditional and Project-Based Engineering Instruction

An outcomes-based assessment process called QQI, an acronym for Quantity-Quality-Improvement, has been developed and pilot-tested in several courses, both traditional and project-based, in mechanical engineering at the University of Texas at Austin. An online version of the QQI survey instrument has been created which automates collection of data and rapid generation of reports to faculty. The QQI process, including the instrument and report generator, research and design basis, and results of pilot testing, are described and department-wide implementation plans are discussed.Copyright

Economic Assessment of Microwave and Radio-Frequency Materials Processing

Dielectric heating has clearly demonstrated its production benefits in many materials processing applications. It is, however, a relatively expensive technology and its use vis a vis less expensive alternatives must be justified by a thorough economic analysis of all factors relevant to the given application. These include not only direct production costs, but also less easily quantified “implicit” factors such as product quality, reduced impact on the external environment, and improved workplace environment. An economic model which includes both production cost considerations and implicit factors in dielectric heating applications is under development. This paper will focus on the capital and operating costs of dielectric heating equipment and the factors which influence these costs. Capital and operating cost information was obtained from radio-frequency and microwave suppliers and consultants in the United States. Mail-out questionnaires were followed up by extensive telephone discussions to correlate and clarify data. The intent was to identify the major cost components of dielectric heating equipment and to summarize the qualitative and quantitative factors which affect them. Since microwave and radio-frequency equipment are distinctly different in design and application, they are treated separately.