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Advanced Energy Systems Division Newsletter Srinivas Garimella, Editor Fall 2001

an active awards program. Publication Opportunities Chair’s Message The Division has seven Technical Com- ’ve been involved mittees, although not all committees are for AESD Authors with various fully active. The technical committees, Several opportunities are available for ASME activities which involve people from industry, gov- AESD authors to publish their technical I ernment, and academia, work hard to cre- articles. These include symposia, the for a number of years, and now I ate very high quality technical programs. monthly , and have the honor and Working to develop technical confer- archival journals. AESD authors are cor- the responsibility to ences, members of the committees come dially encouraged to give a tangible expres- chair the Advanced together under circumstances different sion of their ASME affiliation by consider- Energy Systems from their typical work relationships. ing these publication outlets for their work. Division (AESD). As Authoring a technical paper or encourag- Periodically, AESD has a special section Jerzy Fiszdon chair, I hope to con- ing others to do so, presenting a paper or in the monthly Mechanical Engineering. tinue to conduct the business of the Divi- making general announcements, organiz- Special sections are comprised of articles sion in a professional manner, to enhance ing a technical session or coordinating submitted by various AESD technical the benefits of participation in Division activities with a conference organizer, committees on a rotating basis. Members activities, and to keep up the excellent budgeting time and resources, and gain- interested in participating in this activity professional standing of the Division. I ing exposure to other engineers with dif- should contact the AESD chair and/or am very fortunate in having an excellent ferent technical specialties and different their technical committee chairs. team of executive committee members. I management levels, are all excellent Opportunities for publishing technical count on their guidance and support. We means of professional development. As papers are provided by the symposium have attracted over 900 primary members chair of AESD, I welcome this opportuni- volumes of papers presented at the to our Division. Division activities center ty to thank all who have volunteered their IMECE AESD technical sessions. Normal- on coordinating two technical conferences time and talents to make the Division a ly one or more such volumes are prepared annually, the International Mechanical success and to invite the rest of you to annually, comprising the two dozen or Engineering Congress and Exposition participate in these activities. more papers presented at IMECE. Such (IMECE) and the Intersociety Energy Currently, Dr. S.A. Sherif, the Vice- papers may be eligible for consideration Conversion Engineering Conference Chair of the Division, is preparing a new for the prestigious E. F. Obert Award. (IECEC). Because of tighter funding, we Strategic Plan, and would be glad to share Symposium volumes are available for see a decrease in attendance at confer- this document with anyone requesting it. purchase at IMECE and also may be ences where we meet and get our work I would like to welcome our new incom- ordered directly from ASME technical pub- done, and have to find new ways to ing executive committee member, Dr. lications. Abstracts are generally due in Jan- increase participation. Robert Boehm from the University of uary for papers to be presented at the fol- The Division co-sponsors several con- Nevada, Las Vegas. Dr. Boehm has been lowing IMECE. Authors wanting to partici- ferences held in countries all around the active in the area of Energy Systems for a pate at the 2001 or 2002 IMECE should world. The Division also participates in a long time. I also want to welcome our new check the calls for papers in the monthly once-a-year AESD dedicated issue of representative to the US CADDET Nation- meetings calendar of Mechanical Engineering. Mechanical Engineering, journal articles, al Team Dr. Michael von Spakovsky, Pro- Many AESD authors participate in the and recognizes technical accomplish- ments in Division related areas through (continued on page 2) (continued on page 3)

1 Chair’s Message In addition to the Advanced Energy gram covers the full range of commercial (continued from page 1) Division, he is active in the renewable energy technologies. and Solar Energy Divisions of ASME. He More information about CADDET can fessor and Director of the Energy Manage- is a member of the national Energy Com- be found at http://www.caddet.org. ment Institute at Virginia Tech. mittee of ASME. Finally, the 2001-2002 Executive Com- AES Division Awards and mittee thanks the previous Executive New CADDET-EETIC Keynote Lecture Committee, particularly the leadership of Dr. Salvador Aceves of Lawrence Liver- Representative he AES Division recognizes the out- more National Laboratory, for a job well standing contributions of its mem- r. Michael done. Major highlights are: bers and researchers and educators von T • Increase in AESD membership by 7% in the Advanced Energy Systems area at Spakovsky • Restoring the AESD issue of Mechan- D the annual AESD Luncheon, which is held replaces Jerzy K. ical Engineering at the IMECE. The contributions of these Fiszdon as the repre- • Increasing the number of technical individuals are truly outstanding and are sentative from The committees organizing sessions at one of the main reasons for the continued American Society of the 2001 IMECE, and the number of advancement of energy related technolo- Mechanical Engi- planned technical sessions. gy. The Awards Luncheon also offers the neers to the CAD- I would also like to thank Dr. Gordon opportunity for attendees to hear from a DET - EETIC (Centre M. Reistad for his years of service in vari- leading expert on issues at the forefront of Michael for the Analysis and ous areas of the Division. I hope he will von Spakovsky such research and technology. Dissemination of still participate in the Division activities At the 2000 IMECE, Harry Brandt, Emer- Demonstrated Energy Technologies - Ener- on an informal basis. itus Chairman of the University of Califor- gy and Environmental Technologies Infor- In closing, I would like to urge anyone nia Davis Department of Mechanical Engi- mation Centres) United States National with an interest in the Division or Com- neering, and Chairman of the Board of Team. He has over 13 yrs of teaching and mittees activities to participate. Clean Energy Systems, Inc., gave a thought research experience and over 17 yrs of Jerzy Fiszdon provoking and inspiring talk on “Power industry experience in mechanical engi- Generation with Zero Atmospheric Emis- Boehm Named to neering, power utility systems, aerospace sions.” The talk detailed the concept for a engineering and software engineering. He power plant that uses a combustor/steam Executive Committee received his B.S. in Aerospace Engineering generator based on rocket technology. The r. Robert from Auburn University and his M.S and resulting power plant lends itself very well Boehm is the Ph.D. in Mechanical Engineering from the for CO2 sequestration. Ideally, the CO2 new Execu- Georgia Institute of Technology. He has generated could be used for petroleum D held prior positions at NASA, the power tive Committee extraction. The plans are to build a proto- Member for the utility industry, and the Swiss Federal type of the power plant with 10 MW power Division. He is Pro- Institute of Technology. Since 1997, he has output at Lawrence Livermore National fessor of Mechanical been Professor of Mechanical Engineering Laboratory. Further details of the power Engineering at the and Director of the Energy Management plant can be found in the June issue of University of Neva- Institute at Virginia Tech and has taught “Mechanical Engineering Power.” courses in , industrial The following awards were given at the Robert Boehm da, Las Vegas and Director of the Ener- energy systems, fuel cell systems, and ener- 2000 IMECE: gy Research Center there. His principal gy system design. His research interests The paper entitled “Entropy, Part 1: work has been in the fields of energy con- include computational methods for model- Statistics and its Misleading Disorder; version, heat transfer and thermal system ing and optimizing complex energy sys- and Part 2: Thermodynamics and Perfect simulation, with applications in diverse tems, methodological approaches for the Order” by Elias Gyftopoulos was selected areas such as renewable energy and biolo- integrated synthesis, design, operation and for the Edward Obert Best Paper Award gy. He is a Fellow of the ASME. diagnosis of such systems (stationary In Thermodynamics. He received his BSME and MSME power as well as high performance aircraft The 2000 Technical Commit- degrees at Washington State University. systems), theoretical non-equilibrium and tee Best Paper Award was given to William He was then with the General Electric equilibrium thermodynamics, and fuel cell A. Miller and Majid Keyhani for their paper Atomic Power Equipment Department in applications for both transportation and entitled “The Correlation of Coupled Heat San Jose, California. After completion of distributed power generation. and Mass Transfer Experimental Data for the PhD work at the University of Califor- The CADDET program was first set up Vertical Falling Film Absorption”. nia at Berkeley (1968), he joined the to promote the international exchange of As an example of noteworthy participa- Mechanical Engineering Department at information on energy-efficient technolo- tion of AES division members in other the University of Utah. He has served gies. Later it was extended to cover the ASME divisions, Dr. Srinivas Garimella twice as Chairman of the Department. full field of renewable energy technolo- (with J. W. Coleman) received the best He has been on the faculty at UNLV gies. Since 1997 it includes the GREENTIE paper award for the paper entitled “Visu- since 1990, where he came as Chair to program, covering technologies that miti- alization of Two-phase Flow develop the newly formed Department of gate the emission of greenhouse gases. During Phase Change” presented at the Mechanical Engineering. He also served The Agreement is known as the IEA 2000 National Heat Transfer Conference as Senior Technical Liaison to the US (International Energy Agency) EETIC. in Pittsburgh, PA. Department of Energy from the Universi- CADDET Renewable Energy gathers The following members of the AES ty and Community College System of information on full-scale commercial pro- division were elected Fellows of ASME: Nevada. The Center for Energy Research, jects that are operating in its member Dr. Joseph L. Smith, Jr. in which he is now active, focuses on countries, currently Australia, Denmark, Dr. S.A. Sherif renewable energy technologies, alterna- France, Japan, The Republic of Korea, The Dr. Hameed Metghalchi tive fuels, and energy conservation issues. Netherlands, Norway, Sweden, United Dr. Salvador Aceves He is the author or co-author of 10 books Kingdom, United States and the Euro- Congratulations and a hearty thanks to and over 300 technical publications. pean Commission. The CADDET pro- all these awardees! 2 Reports from the Committees Direct Thermal Power Shiva Prasad of Dresser-Rand company The next full meeting of the committee was elected Chair, along with Dr. Abdi will be held at the 2001 IMECE. Anyone Conversion and Thermal Zaltash of Oak Ridge National Laboratory interested in additional information on Management as the Vice-Chair and Dr. Laura Schaefer the committee, or in participating in its This committee promotes research and of the University of Pittsburgh as the Sec- activities is welcome to attend. development in all areas of direct conver- retary to serve for a period of two years. Jayanta S. Kapat sion of heat to electric power without any Seven technical sessions and one panel are moving parts or thermal management of being organized for the 2001 IMECE. The committee has also instituted an award Superconductivity energy. Direct thermal energy conversion This committee provides a forum for devices include thermionics, thermo- for the best student paper, and would appreciate university faculty encouraging presenting the most recent progress in the electrics, AMTEC (alkali metal thermal to field of applied superconductivity. The electric converter), and TPV (thermopho- their students to submit papers on their work at future conferences. committee continues its efforts in spon- tovoltaics). All areas of thermal manage- soring paper sessions including those co- ment including aircraft and spacecraft, The committee seeks and is always open for ASME members interested in sponsored by other ASME committees. A ground vehicles, electric component and paper session on “Cryogenic Engineer- power systems, and industrial energy active participation and contribution of their time, effort and ideas for its evolu- ing” jointly sponsored by this committee, systems are covered. The committee par- the Heat Transfer Division K-18 Commit- ticipates in the IECEC, IMECE, and other tion and growth. B. G. Shiva Prasad tee on Low-Temperature Heat Transfer, conferences related to advanced energy and Process Industries Division Cryogen- systems. During this year, the committee ics Technical Committee, will be held at has organized four sessions for the Inter- Energy Systems the 2001 IMECE. society Energy Conversion Engineering New members are sought to bring in Conference held at Savannah, Georgia, in Miniaturization This committee organized a successful new ideas and to help coordinate future July-August, 2001, and one session for the activities. Information on this committee IMECE to be held at New York city, in and well-attended panel session at the 2000 IMECE in Orlando, FL, entitled “Panel on can be obtained by contacting the com- November, 2001. mittee chairman, Dr. Ming Chyu (contact Muhammad Rahman Miniature Energy, Chemical and Biological Systems.” The session discussed the cur- information elsewhere in this newsletter) rent state-of-the-art in different miniature vice chairman, Dr. John R. Hull, Argonne Heat Pumps engineering systems. The key focus was on National Laboratory, (708) 252-8580, or The main objective of the Heat Pump complete systems rather than individual secretary, Dr. P. E. Phelan, Arizona State technical Committee is to help advance components. The benefits and challenges University, (480) 965-1625. the state of the art of the science and tech- of miniaturization, along with possible Ming-C. Chyu nology of Heat Pumps, which play an applications, were discussed by the pan- essential role in the lives of human beings. elists. Both meso-scale and micro-scale sys- System Analysis The current trend towards energy scarcity tems were presented. The session featured During the year 2000, the Committee and the scare of depletion of its resources speakers from academia, industry and organized its sixteenth symposium on is driving science and technology towards government, who provided overviews on “The Thermodynamics and the Design, innovation in the art of energy produc- microturbine projects and miniaturized Analysis and Improvement of Energy tion, storage and transmission. Efficiency systems under development including a System,” held at the IMECE in Orlando, improvement has attained the greatest mesoscopic pump, a PolyMEMS actuator, FL. The symposium organizer was importance in the energy industry and an integrated mesosniffer, and a miniatur- Michael von Spakovsky. The symposium hence the refrigerators, air conditioners ized cytometer. Thermoelectric micro- included 49 papers, which were orga- and other heat pumping devices are power generators, an automotive fuel pro- nized in 10 sessions. These papers were expected to perform with very little ener- cessor for producing hydrogen for PEM submitted by researchers in six conti- gy loss. Consequently, this is an era with fuel cells, an in situ propellant production nents, a clear indication of a very strong great challenges and promise for engi- plant for Mars, and a man-portable heat international participation. The Fuel Cell neers, researchers and technologists who pump for cooling soldiers in the field in sessions and the Panel discussion session want to make the art, science or technolo- hot climates were also discussed. The Sustainability of Energy Conversion gy of heat pumping as their career. The June 2001 issue of Mechanical Technologies in the 21st Century were The committee organizes symposia and Engineering magazine contained a fea- very well attended. panels to bring together researchers work- ture article, authored by Professor The Committee is also a co-sponsor of ing in various fields relating to the funda- Richard B. Peterson of Oregon State Uni- the yearly international ECOS (Efficiency, mental understanding and development of versity - the current chair of this commit- Costs, Optimization, Simulation and various types of heat pumps. During the tee, on the miniaturization and integra- Environmental Aspects of Energy Sys- 2000 ASME IMECE held at Orlando, there tion of the components necessary for tems), which was held in July 2000 in were 5 well attended technical sessions and advanced energy and chemical systems. Holland. The attendance was over 200, one panel session. The paper by A. Laveau, A second article from the same issue, co- with a big attendance from researchers in J. S. Kapat, L. C. Chow, E. Enikov, and K. authored by Professor Patrick E. Phelan the U.S.A. The ECOS 2001 was held in B. Sundaram, on the “Design, Analysis, of Arizona State University - a member of summer 2001 in Istanbul, Turkey. and Fabrication of a Meso-Scale Centrifu- this committee, had reference to minia- Abel Hernandez is the organizer of the gal ” has been adjudged the turization of cryogenic cooling systems. 2001 IMECE symposium. There were 48 best paper for the year 2000 and the award, The committee met at the 2000 IMECE, abstracts sent for consideration, from the which also carries a $500 prize, will be pre- and discussed a initiating a concerted following countries: China, Korea, United sented at the 2001 IMECE. drive at membership and a web presence. States, Italy, Colombia, Japan, Spain, Ger- The committee meets once a year at the The committee will organize two sessions many, Greece, Mexico, Poland, Bulgaria, IMECE. At the last meeting, Dr. B.G. at the 2001 IMECE. continued

3 Committees bers, in preparation for sending the draft Publication Opportunities continued out for industry review. (continued from page 1) Tony Leo Switzerland. From these about 41 papers Stirling Engines annual IECEC (Intersociety Energy Conver- are accepted, with the symposium con- There has been relatively little large- sion Engineering Conference) held during sisting of 11 technical sessions and two scale development in the Stirling engine the summer. IECEC 2001 was hosted by panel sessions. community in the past year. While it is ASME in July at Savannah, GA. Nearly The Committee has two awards each expected that the recent return of energy every summer for several years AESD also year, the Best Paper award of $500, and issues to the public consciousness will has participated in symposia held outside the Best Student Paper award of $400. reinvigorate interest in these efficient and the United States at various memorable The award winners for year 2000 are: clean energy converters, in the mean time, sites. The 2001 event, ECOS 2001 (Effi- Best Paper: Betts, D. A., Roan, V.P., and companies and researchers interested in ciency, Costs, Optimization, Simulation Fletcher, J. H. for their paper entitled this technology have focused on specialty and Environmental Aspects of Energy “Discussion and Analysis of Gas Uti- applications. Among these, Stirling Tech- Systems) was held in July at Istanbul, lization in a Phosphoric Acid Fuel Cell nology Company in Washington State has Turkey. ECOS 2002 will be held in Berlin, Engine During Idle Operation” had good success with small free-piston Germany in July, 2002. Papers for all such Best Student Paper: Munoz, J. R. (and power units for NASA’s deep space mis- conferences are reviewed according to M. von Spakovsky) for the paper entitled sions. In other power-generation news, it ASME standards and the symposium vol- “The Use of Decomposition for the large appears that the DoE has decided to close umes are published variously by ASME or Scale Synthesis/Design Optimization of down the Concentrating Solar Thermal commercial publishing houses. For infor- Highly Coupled, Highly Dynamic Energy power programs, of which Stirling mation concerning upcoming conferences, Systems” engines were a key part (converting con- authors should consult the meetings cal- The Committee held its yearly meeting centrated solar heat into mechanical and endar in Mechanical Engineering. during the 2000 IMECE. The following electrical output). This has adversely Additional outlets for technical articles are the new Executive Group members affected companies such as Stirling Ther- by AESD authors are provided by the for 2001: George Adebiyi, Chairman; Vin- mal Motors, who was the prime vendor archival journals, Journal of Engineering cent Wong, Vice Chair; Abel Hernandez, for the solar efforts of SAIC (through San- for Gas Turbines and Power, Journal of Symposium Chair; Marc Rosen, Assistant dia/DoE). Overseas, WhiperTech of New Turbomachinery, and Journal of Energy Vice Chair. Zealand continues to promise imminent Resources Technology, and the monthly, George Adebiyi production of their stand-alone gas-fired Mechanical Engineering. Owing to peer generators, which are well-packaged, review requirements and some queuing compact designs. of accepted papers before publication, a Hydrogen Technologies year to 18 months can elapse between This committee provides a forum for In a significant development of the year paper submission and publication. Still, presenting the most recent progress in the 1999/2000, Los Alamos National Lab archival journals are the appropriate field of hydrogen technologies for energy, (LANL), a center for thermoacoustics forum for articles of enduring value. including hydrogen utilization, storage, work, announced a hybrid Stirlng-acous- Prospective authors should see current production, systems analysis, and safety. tic engine that operates without the some- issues of the journals for instructions con- The committee is organizing a session on times-troublesome displacer component, cerning the submission of articles. Hydrogen Energy Technologies in the using just the gas inertia to achieve the For answers concerning your questions Symposium on Thermodynamics and the desired gas motion and pressure waves. about AESD publishing opportunities Design, Analysis, and Improvement of These developments might eventually contact M.J. Moran (contact information Energy Systems as a part of the 2001 result in a lower-cost small system for elsewhere in this newsletter.) IMECE. Papers on hydrogen production self-powering home . M.J. Moran and storage have been submitted and are Other Stirling-based groups have con- currently under review. The symposium centrated on cooling applications, Sun- also has a session on fuel cells technology, power, STC, and CFIC have all made AES Division which is of interest to people working on advances toward commercial production Participation in IECEC hydrogen technologies. of cryocoolers based on the Stirling prin- This year’s 36th IECEC was hosted by The committee invites all who are inter- ciple, either directly or through the recent ASME with a theme of “Energy Technolo- ested or working in the field of hydrogen thermoacoustic and pulse-tube variant gies Beyond Traditional Boundaries” at the technologies for energy, including hydro- developments. Sunpower is preparing Westin Hotel in Savannah, Georgia from gen utilization, storage, production, sys- facilities for production of its small units July 29-August 2, 2001. The AESD co-spon- tem analysis, and safety, to participate in (10’s of watts @ 6—80K). Sunpower has sored several technical sessions on “Build- these Symposium sessions and become licensed its technologies to both STI and ing Energy Systems”, “Cogeneration and active members for future events. LG Electroniucs (of Korea) for the cooling Thermal Energy Storage” and “Electric Joel Martinez-Frias of cell-phone antennas. STC continues to Power Systems” as well as Advanced Heat offer a lab cooler. CFIC is collaborating Pumps and other topics. The 37th IECEC with Praxair, Inc., to commercialize larger will be hosted by IEEE in Washington, D. Fuel Cells resonant systems (100’s to 1000’s of watts The fuel cell committee activity has C., July 28 - August 1, 2002 at the Omni- at 30-150K) for condensation of industrial Shoreham hotel. There will be plenty of been limited recently to the PTC-50 fuel gasses and of high-Tc super- cell performance test code work, which is opportunities for you to volunteer to help conducting power systems. It is in minia- in organizing sessions, writing papers, progressing well. The PTC-50 committee ture cryocooler where Stirling has made is drafting a performance test code for reviewing papers, etc. The contact informa- its mark so far, with TRW and Raytheon, tion for this conference is as follows: fuel cells similar to ASME codes for gas and in England, Hymatic, manufacturing turbines (PTC-22), or overall performance Dr. William D. Jackson, General Chair thousands of small tactical Stirling cry- HMJ Corporation, P. O. Box 470 (PTC-46). A meeting was held at ASME ocoolers for the military every year. Per- headquarters on June 12 to review the Kensington, MD 20895 haps this is the year that this technology (301) 946-1586 draft document. This document is now will reach commercial application. being reviewed by the committee mem- [email protected] John Corey Sriram Somasundaram 4 Scaling Laws in Miniature Heat Engines Jay Kapat and Louis Chow Introduction sitic heat transfer from the turbine to the This important design relation for Compact and portable power generation compressor. However, if it is assumed turbo-machines poses a serious design devices are key components in many com- that the compressor and the turbine are challenge for a miniature system, since mercial, consumer and military systems, separated by a ceramic layer with a thick- compact size requires small radii, high such as portable computers, and cellular ness of 5 mm and a thermal conductivity reliability requires slow rotational speed, phones. So far batteries have been the only of 1 W/mK, and the typical temperature whereas efficient operation requires large providers of the required portable power. difference across the ceramic separation pressure ratio. Thus miniaturization can However, as the user systems become layer is 1248 K (the difference between become an impediment to having a large more complicated and power hungry, the average temperatures in the turbine system efficiency. As a result, the system even the state-of-the-art battery technology and the compressor), then the heat flux designer is left to use innovative variation becomes less and less appealing. For across the layer is 25 W/cm2. This heat (such as regeneration or reheating) to the example, a proposed next generation sol- flux corresponds to 792 W of parasitic basic thermodynamic cycle in order to dier system for army requires power gen- heat transfer between the turbine and the obtain acceptable efficiency in spite of a eration devices with specific energy of at compressor, for a circular device with a low-pressure ratio. least 2000 W-hr/kg for missions exceeding cross-sectional diameter of 2.5 inch. Obvi- The design of a miniature turbomachine 72 hours of duration, whereas the most ously, this amount of heat transfer is is often further complicated with the advanced battery technology can provide absurd for a device that produces a net requirement of a low mass flow rate, corre- around 200 W-hr/kg. Naturally alternate power of only 20 W. In other words, such sponding to a low total power (which is power generation devices such as fuel cells a device cannot produce any net power if typically imposed by the system require- and heat engines are receiving more and parasitic heat transfer between the hot ment or by the associated miniature elec- more attention. This article focuses on and cold ends of the device is allowed tric components such as motor or genera- miniature heat engines and the relevant without any special consideration for tor). In this case, even a moderate tip scaling laws that should be considered thermal isolation of the two sides (Finger speed as required for any decent pressure during design for compact and portable et al., 2002). This problem is further com- ratio can cause large tangential velocities, power generation. plicated if we consider that thermal isola- Utangential, compared to the radial compo- Heat engines based on Brayton cycles tion in a Brayton-cycle-based system typi- nent, Uradial, at the blade tips of a rotating and internal combustion engines are the cally means mechanical isolation of com- stage, as can be seen from the following most popular heat engines that are cur- pressor and turbine, which are located on two equations. In any radial machine, the rently being looked at for possible minia- the same shaft in conventional designs. mass flow rate at the blade tips can be turization, primarily by researchers at Thus, designers of such a system have to expressed as (Laveau et al., 2000) MIT and UC Berkeley, respectively. There rethink conventional design philosophy m˙ =2πρR bU ,(2) are also less proven technologies such as and employ innovative modification if tip radial piezoelectric heat engine proposed by they have to reduce parasitic heat trans- where b is the blade height, and ρ is the researchers at Washington State Universi- fer. In a miniature rotary Wankel engine, local density. From the velocity vector at ty, or knock engines being worked on by thermal separation of hot and cold cham- the blade tip, the tangential component researchers at Honeywell. However, this bers, which coexist at the same time, ther- can be expressed as (Wilson and article focuses on proven and tested mal isolation between the hot and cold Korakianitis, 1998) cycles such as Brayton and Otto. ends is even more difficult. α Rest of this article illustrates six design This problem is more prominent at Utangential=Utip±Uradial ·tan( w). (3) issues that must be simultaneously con- smaller scales, whereas it is insignificant at α Here, w is the relative flow angle, sidered in the design of a miniature sys- conventional scale. This is so because the which is typically close to the blade angle, tem based on Brayton or Otto cycle. ratio of parasitic heat transfer rate to the β, and the +/- sign in the equation overall power output scales as the inverse depends on the type and design of the tur- Separation of Hot and Cold Ends of the linear dimension squared, for the bomachine. In miniature designs, since a same specific power and the same operat- Any heat engine requires a hot and small b-to-Rtip ratio will produce large vis- cold end, corresponding to the hot and ing temperatures. Similar argument can be cous losses, b cannot be arbitrarily cold reservoirs in the thermodynamic applied to all other heat engines running reduced. For good aerodynamic design, cycles. In a miniature system, these two on different power cycles, such as Otto and blade angle cannot approach 90° and is Diesel. The problem can be much more ends are physically close, leading to a typically much less. As a result, Utip is parasitic heat transfer from the hot to the severe with the use of common micro-fab- often much larger than the second term on cold end that does not produce any work rication materials such as Si (with thermal the right-hand side of equation (3), and conductivity of 140 W/mK) or SiC. and bypasses the thermodynamic cycle. Utangential is much larger than Uradial, leading Depending on the actual design, this par- to a large loss in the diffuser for a centrifu- asitic heat transfer can be significant or Scaling in Turbomachinery gal compressor or inlet guide vane for a even a “show-stopper”. This is illustrated This issue pertains to only those systems radial inflow turbine. This argument lim- with a hypothetical example below. that employ dynamic or turbomachine its the blade tip speed that in turn limits Let us consider a system based on the components, where the size, rotational the pressure ratio across the components simple Brayton cycle, with ideal compo- speed and the pressure ratio across the in a stage. This design problem can be nents, and with a pressure ratio of 2.5, a machine are all related. To be more specif- alleviated to some extent through the use compressor inlet temperature of 300 K, a ic, the change of specific across a of multiple stages at the cost of design turbine inlet temperature of 1800 K and turbomachine is proportional to the square complication and system size. net power output of 20 W. In that case, of the blade tip speed (Utip), which is pro- Any system design based on positive- with a cold-air cycle analysis (with 1.4 as portional to the product of tip radius (Rtip) displacement, rather than dynamic com- the ratio of specific heats), the compressor and the rotational speed (RPM): ponents such as a rotary Wankel engine, exit temperature is 390 K and system effi- ∆h∝U2 ⇒∆h∝(R ·RPM)2.(1)can ignore this design issue. However, it ciency is 23%, in the absence of any para- tip tip should be noted that internal combustion 5 engines have lower overall system effi- ciencies than gas turbine engines because of the inherent system layouts and higher losses, as can be seen from the conven- tional-sized systems.

Need for Small Relative Tolerance Losses in any real component are direct- ly related to the small relative tolerance. This relative tolerance can be expressed as the clearance-to-radius ratio in a recipro- cating or Wankel device or the tip-gap-to- Figure 1. An Inflow Turbine Fabricated by Micro-Stereolithography. tip-radius ratio in a turbomachine. In con- ventional-sized gas turbines, for example, niques for micro-fabrication and newer The axial heat conduction comes from two this ratio typically varies from 1% (for materials that can be micro-fabricated. For sources: the heat conducted in the solid 200+ MW machines) to 4% (for 1 MW this reason, an effort at the University of wall and in the flowing fluid in the chan- machines). It should be noted that as the Central Florida is considering use of nels. To neglect the axial heat conduction relative tolerance increases, component micro-stereolithography with absolute tol- in the fluid flow, the Peclet number must efficiencies drop from near 90% values for erance of about 10 microns or less (Figure be much greater than 1, which requires a gas turbines for 200+ MW power genera- 1) and a special polymer-derived ceramics relatively large Reynolds number and tion systems to 60% for 50 kW systems. that is not affected until around 1900 K. hence large pressure drop. A small axial For internal combustion machines, this conduction through the solid wall requires ratio is typically larger thus contributing Need for Regeneration the use of thin walls of a material with a to larger losses. Since even with the cur- As illustrated earlier, a simple Brayton relatively low thermal conductivity. Thus rent state-of-the-art micro-fabrication, an cycle cannot provide the efficiency in order to minimize axial conduction, a absolute tolerance of less than 1 to 10 required for the example used, even if all careful optimization needs to be per- microns cannot be realized in a real com- the components are ideal. This requires formed. It should be noted that axial con- ponent such as a turbine or a compressor, modifications to the simple cycle, such as duction is not typically a problem in large a specified value for the maximum allow- regeneration and reheating. In particular, heat exchangers where Peclet number as able relative tolerance dictates the mini- regeneration is the key to any practical well as ratio of length to mum component size. Thus a 1% relative system, as has been proven in commercial wall thickness are quite large. tolerance with an absolute tolerance of 10 human-sized “micro-turbines” producing microns requires that the component 50+ kW that have been derived through Conclusion radius be no smaller than 1 mm with the years of system optimization. For systems Typical design rules that are applicable size of the overall, packaged component such as the ones considered here (with for components and systems of conven- approaching 1 cm. This argument suggests output of the order of 100 W or even less), tional size may not be applicable to that any design for a heat engine with a use of regeneration is imperative, where miniature systems and components. Sim- practically useful efficiency requires a small size and reasonable rotational speed ple repackaging of a conventional design meso-scale, rather than a micro-scale, size. preclude a large pressure ratio. with micro-fabricated components will It should be noted that common heat not provide the optimum performance, or Need for High Temperature Materials engines such as aircraft engines or large may not even work. A miniature system Even a modest value for system effi- utility-sized power generation plants do must require a fresh design optimized for ciency requires a rather high temperature not use regeneration since heat exchang- smaller size. Moreover, such a system for the hot end of the heat engine. As an ers for regeneration in these large systems should use components that are opti- example, let us consider a palm-sized will be prohibitively expensive and large. mized for small size, are micro-fabricated power generation device, which is based Also, for heat engines with pressure ratios wherever necessary and make use of the on Brayton cycle, with an electrical output larger than a critical value for a fixed scale advantages in miniaturization. of 20 W and a specific energy of 2000 W- value of the maximum cycle temperature, Further information about this technology hr/kg on a 72 hour mission, and which regeneration hurts the overall perfor- can be obtained from Jay Kapat or Louis Chow runs on a hydrocarbon fuel (such as JP-8) mance, as the compressor exhaust would of University of Central Florida at jkapat@mail. with a specific energy content of 12000 W- be hotter than the turbine exhaust. Hence, ucf.edu or [email protected], respectively. hr/kg. The required system efficiency in if a designer for miniature systems start this case is 28.7% even for a device weight with the design for such a large system, it References of 300 g. This required efficiency is larger is easy to overlook the importance of Finger, G. W., J. S. Kapat, L. C. Chow, 2001, than even the efficiency of 23% obtained regeneration. “Design and Analysis of a Rotary Wankel earlier for an ideal device based on a sim- Use of a heat exchanger for regenera- Compressor,” to be presented at the Interna- ple Brayton cycle with the hot reservoir tion raises further issues. Miniaturization tional Mechanical Engineers Conference and Exposition, November 11 - 16, New York. temperature of 1800 K. This temperature produces a larger surface-area-to-volume ratio, which helps in transport processes Laveau, A., J. S. Kapat, L. C. Chow, E. Enikov, is high even for most metals, let alone Si and K. B. Sundaram, 2000, “Design, Analy- or SiC, the most common materials for such as heat transfer leading to higher sis and Fabrication of a Meso Scale Centrifu- micro-fabrication. The same argument volumetric transport coefficient. This fea- gal Compressor,’ ASME Proceedings, AES holds good for Otto- or Diesel-cycle based ture is helpful for a miniature heat Vol. 40, pp. 129 - 137. machines. Even if the Brayton cycle-based exchanger. However, efforts to obtain a Wilson, D. G., and T. Korakianitis, 1998, The device illustrated above is modified with large effectiveness and small pressure Design of High-Efficiency Turbo-machinery introduction of regeneration (as noted in drops require a large number of short, and Gas Turbines, 2nd ed., chap. 9, Prentice the next section), a hot-end temperature parallel ducts with small cross-sections Hall. Zhou, L., J. S. Kapat, L. C. Chow, and X. Li, in excess of 1500 K is needed. for both hot and cold fluids. Axial conduction in a miniature heat 2000, “Design of a High Effectiveness Micro The combined requirement for a high heat Exchanger for Mars Applications,” Proc. temperature operation and a small relative exchanger can significantly reduce the heat SAE Power Systems Conference, San Diego, tolerance suggests the use of newer tech- exchange effectiveness (Zhou et al., 2000). Oct 31 - Nov 2, vol. P-359, pp. 109 - 116.

6 Advanced Energy Systems Division 2000-2001 Chair Special Publications Liaison Energy Systems Miniaturization Jerzy Fiszdon Michael J. Moran Richard B. Peterson Dept. of Mechanical Engineering Dept. of Mechanical Engineering Department of Mechanical Engineering Minnesota State University The Ohio State University 204 Rogers Hall Mankato, MN 56001 206 W. 18th Ave Oregon State University B: (507) 389-2115 F: (507) 389-5002 Columbus, OH 43210-1154 Corvallis, OR 97331 [email protected] B: (614) 292-6064 F: (614) 292-3163 B: 541-737-7095 F: 541-737-2600 [email protected] [email protected] Vice Chair S. A. Sherif AES Liaison to ASME Energy Commit- Fuel Cell Power Systems Department of Mechanical Engineering tee Tony Leo University of Florida Gordon M. Reistad B: (203) 825-6035 228 MEB, Box 116300 Mechanical Engineering Dept. [email protected] Gainesville, FL 32611-6300 Oregon State University B: (352) 392-7821 F: (352) 392-1071 Rogers Hall, Rm 204 Heat Pumps [email protected] Corvallis, OR 97331-6001 B. G. Shiva Prasad B: (503) 737-3441 F: (503) 737-2600 Aero-Thermodynamics Group Secretary/Treasurer [email protected] Steam Turbine Division Sriram Somasundaram Dresser-Rand Battelle-Pacific Northwest Labs. IECEC Program Representative 37 Coats St. Battelle Boulevard, P.O. Box 999 MS K5- Sriram Somasundaram Wellsville, NY 14895 20 Battelle-Pacific Northwest Labs. B: (716) 596-3213 F: (716) 596-3233 Richland, WA 99352-0999 Battelle Boulevard, P.O. Box 999 MS K5- [email protected] B: (509) 375-6842 F: (509) 375-3614 20 [email protected] Richland, WA 99352-0999 Hydrogen Technologies B: (509) 375-6842 F: (509) 375-3614 Joel Martinez-Frias Past Chair [email protected] Lawrence Livermore National Laboratory Salvador M. Aceves PO Box 808, L-640 Lawrence Livermore National Laboratory Media Editor Livermore, CA 94551 7000 East Avenue, L-140 Srinivas Garimella B: (925) 422-0864 F: (925) 423-0618 Livermore CA 94551 Dept. of Mechanical Engineering [email protected] B: (925) 422-0864 F: (925) 423-0618 Iowa State University [email protected] 2030 H. M. Black Engineering Bldg Superconductivity Ames, IA 50011-2161 Ming-Chien Chyu Members B: (515) 294-8616 F: (515) 294-3261 Texas Technical University Srinivas Garimella (Programs) [email protected] Dept of Mechanical Engineering Dept. of Mechanical Engineering PO. Box 41021 Iowa State University ASME Staff Lubbock, TX 79409-1021 2030 H. M. Black Engineering Bldg Jim Reffelt B: (806) 742-0965 F: (806) 742-3540 Ames, IA 50011-2161 3 Park Avenue [email protected] B: (515) 294-8616 F: (515) 294-3261 New York, NY 10016-5990 [email protected] B: (212) 705-7055 F: (212) 705-7671 Systems Analysis [email protected] George Adebiyi Hameed Metghalchi (Honors and Mechanical Engineering Department Awards) Ramon Johnson Mail Stop 9552, 210 Carpenter Building Mechanical, Industrial & Mfg. Engineer- Administrator, Engineering Programs Mississippi State University ing Engineering Programs Dept. Mississippi State, MS 39762 Northeastern University Mail Stop 22W3 B: (662) 325-7314 F: (662) 325-7223 360 Huntington Ave ASME International [email protected] Boston, MA 02115 Three Park Avenue B: (617) 373-2973 F: (617) 373-2921 New York, NY 10016-5990 U.S.A. Conference Liaisons [email protected] B: 212-591-7054 F: 212-591-7671 Fluidized Bed Combustion [email protected] John P. Mustonen Robert F. Boehm (Membership Develop- Stone & Webster Engineering Corp. ment) TECHNICAL COMMITTEES 245 Summer Street Professor of Mechanical Engineering and Direct Thermal Power Conversion and Boston, MA 02210_1119 Director of the Energy Research Center Thermal Management B: (617) 589-8626 F: (617) 589-2706 Howard H. Hughes College of Engineer- Muhammad M. Rahman ing Department of Mechanical Engineering Stirling Engines UNLV Box 454027 University of South Florida John Corey Las Vegas, NV 89154 4202 E. Fowler Avenue, ENB 118 Clever Fellows Innovation Consortium B: (702) 895-4160 F: (702) 895-3936 Tampa, Florida 33620 Inc. [email protected] B: (813) 974-5625 F: (813) 974-3539 302, 10th Street, Troy, NY 12180 [email protected] B: (518) 272-3565 F: (518) 272-3582 [email protected]

7 AES Division Extremely Active at IMECE New York (November 11-16, 2001)! Mark your Calendars!

he AES Division has planned a very stimulating technical program at this year’s IMECE in New York, NY. A total of 19 sessions including panel sessions on current topics will be held. The papers scheduled in these sessions include numerous contributions Tfrom outside the US and from industry, demonstrating the wide-ranging and global appeal of the technical topics being addressed by the AES Division. A list of session titles is provided below. Please be sure to participate in these informative sessions and add your valuable input wherever possible, especially during the discussion period at the end of each paper or panel presentation. We hope to see you there.

Direct Thermal Energy Conversion/Thermal Management Technologies and Systems Direct Thermal Energy Conversion/Thermal Management Technologies and Systems

Heat Pump and Refrigeration Systems Design, Analysis, and Applications Heat and Mass transfer in Heat Pumps Fluid Mechanics and Heat Transfer in Positive Displacement CFD Application to Heat Pump Systems and Components Heat Actuated Sorption and Desiccant Heat Pumps Emerging and New Technologies for Heat Pump and Refrigeration Cycles - I and II Transcritical Cycles for Refrigeration and Heat Pumping CFD for Positive Displacement Compressors - Challenging Issues? (Panel Session)

Micro and Mesoscale Energy Systems and Conversion Devices Micro and Mesoscale Energy Systems and Conversion Devices

Thermodynamics and The Design, Analysis, and Improvement of Energy Systems Energy Systems and Design (2 sessions) Fundamentals of Thermodynamics Fuel Cell Technology Applied Thermodynamics Thermodynamics and Energy Systems Thermodynamics of Energy Systems and the Environment Symposium on Hydrogen Technologies Thermodynamics of Power and Process Plants Exergetic Analysis Applied to Aircrafts Design (Panel Session) Fuel Cells: the State of the Art and Future Directions and Impacts (Panel Session) Join the ASME Advanced Energy Systems Division Today!

To join the Division and/or ASME, fill out and mail the following form to ASME Headquarters at the following address or connect to http://www.asme.org.

To: ASME International, 3 Park Avenue, New York, NY 10016-5990 From: ______Date: ______Affiliation: ______Phone: ______E-mail: ______Address: ______City: ______State: ______Zip: ______Country: (if not USA): ______[ ] I wish to become a member of the ASME Advanced Energy Systems Division [ ] I am an ASME member [ ] I wish to join the ASME; please send me a membership application I would like to be active in the Advanced Energy Systems Division. Please contact me. [ ] Technical Interests and Comments: ______

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