Cooling for Microsystems: Miniaturization Prospects for Pulse Tube Cryocooler

Regenerative Kryokühler wie Stirling-, Gifford-McMahon- und Pulsrohr-Kryokühler besitzen große Vorzüge wie geringe Größe, niedrige Kosten, hohe Zuverlässigkeit und gute Kühlleistung. Diese Vorzüge führten dazu, dass sie viele Anforderungen von IR- und supraleitenden Anwendungen erfüllen. Unter diesen Kryokühlern gibt es eine Maschine, die als Pulsröhren-Kryokühler (PTC) bezeichnet wird, die ausgezeichnete Vorzüge aufweist und das Potenzial hat, für On-Chip- und Mikrosystem-Anwendungen miniaturisiert zu werden. In dieser Arbeit werden die Miniaturisierungsaspekte dieser Maschine anhand verschiedener numerischer Analysen und computergestützter fluiddynamischer (CFD) Simulationsmodelle untersucht. In dieser Arbeit wird eine Analyse des komplexen Betriebs für das Röhrenelement für einen Orifice Pulse Tube Cryocooler (OPTC) vorgeschlagen. Dies wird durch eine Phasenanalyse unter Verwendung fundamentaler thermodynamischer Beziehungen erreicht, um die mit dieser Maschine verbundene Kühlleistung näherungsweise abzuschätzen. Darüber hinaus wird der Effekt des Phasenverschiebungswinkels veranschaulicht, indem eine Analogie zwischen dem Phasenverschiebungsmechanismus und einem Serien-RLC-Schaltungsmodell gebildet wird. Anschließend wird ein eindimensionales Modell vorgestellt, das auf Massen- und Energieerhaltungsgleichungen basiert; das reduzierte Modell wird numerisch für die Temperatur und Geschwindigkeit des Gases entlang des Rohrs gelöst, um den Massenstrom und die zeitlich gemittelten Enthalpieströme am kalten und heißen Ende des Rohrs zu bestimmen. Die Erkenntnisse aus der eindimensionalen Analyse werden mit den bisherigen Ergebnissen der Phasoranalyse verglichen. Der Regenerator ist eine kritische Komponente in diesen Kryokühlern mit geschlossenem Kreislauf. Die Arbeit präsentiert eine eindimensionale numerische Analyse der idealisierten thermischen Gleichungen der Matrix und des Arbeitsgases innerhalb des Regenerators. Der Algorithmus prognostiziert die Temperaturprofile des Gases während des Aufheizens und Abkühlens sowie die Matrix-Knotentemperaturen. Es wird untersucht, wie die Länge und der Durchmesser des Regenerators, die geometrischen Parameter der Matrix, die Anzahl der Wärmeübertragungseinheiten und der Volumenstrom die Leistung eines idealen Regenerators beeinflussen. Es wird auch ein achsensymmetrisches 2D-CFD-Modell vorgeschlagen, um das Modell des idealen Regenerators zu bewerten und zu validieren. Darüber hinaus wird ein analytisches Verfahren entwickelt, um die im Regenerator vorhandenen Verluste abzuschätzen. Die Ergebnisse werden mit denen einer anderen Software, genannt REGEN, die vom NIST entwickelt wurde, verglichen. Danach wird über eine achsensymmetrische numerische CFD-Simulation berichtet, die die oszillierenden Strömungs- und Wärmeübertragungsprozesse in einem Inertanz-Pulsrohr-Kryokühler aufzeigt. Die Auswirkungen der Betriebsfrequenz werden untersucht, und die Auswirkungen der reduzierten Größe des Systems bei Betrieb mit hoher Frequenz auf die Kühlleistung des Systems werden untersucht. Darüber hinaus wird eine spezielle Software namens Sage und CFD-Modellierung verwendet, um Ultra-Miniatur-PTC-Modelle zu entwickeln. Ihre Leistungsparameter werden untersucht und ihre Eignung für On-Chip- und Mikrosystemanwendungen wird bestimmt

40 K Neon liquid energy storage unit

Cryocoolers have been progressively replacing the use of the stored cryogens in cryogenic chains used for detector cooling, thanks to their higher and higher reliability. However, the mechanical vibrations, the electromagnetic interferences and the temperature fluctuations inherent to their functioning could reduce the sensor’s sensitivity. In order to minimize this problem, compact thermal energy storage units (ESU) are studied, devices able to store thermal energy without significant temperature increase. These devices can be used as a temporary cold source making it possible to turn the cryocooler OFF providing a proper environment for the sensor. A heat switch is responsible for the thermal decoupling of the ESU from the cryocooler’s temperature that increases when turned OFF. In this work, several prototypes working around 40 K were designed, built and characterized. They consist in a low temperature cell that contains the liquid neon connected to an expansion volume at room temperature for gas storage during the liquid evaporation phase. To turn this system insensitive to the gravity direction, the liquid is retained in the low temperature cell by capillary effect in a porous material. Thanks to pressure regulation of the liquid neon bath, 900 J were stored at 40K. The higher latent heat of the liquid and the inexistence of triple point transitions at 40 K turn the pressure control during the evaporation a versatile and compact alternative to an ESU working at the triple point transitions. A quite compact second prototype ESU directly connected to the cryocooler cold finger was tested as a temperature stabilizer. This device was able to stabilize the cryocooler temperature ((≈ 40K ±1 K) despite sudden heat bursts corresponding to twice the cooling power of the cryocooler. This thesis describes the construction of these devices as well as the tests performed. It is also shown that the thermal model developed to predict the thermal behaviour of these devices, implemented as a software,describes quite well the experimental results. Solutions to improve these devices are also proposed.Fundação para a Ciência e a Tecnologia - SFRH/BD/70427/2010 scholarship; PTDC/EMEMFE/ 66533/2006; PTDC/EME-MFE/101448/2008; PEst-OE/FIS/UI0068/2012-2014); FCT-Embaixada de França — Programa Pessoa 2011/201

MAGESTIC: Magnetically Enabled Structures Using Interacting Coils

In our NIAC Phase I study, awarded September 2011, the MIT Space Systems Lab (MIT SSL) began investigating a new structural and mechanical technique aimed at reducing the mass and increasing the stowed-to-deployed ratio of spacecraft systems. This technique uses the magnetic fields from current passing through coils of high temperature superconductors (HTSs) to support spacecraft structures and deploy them to operational configurations from their positions as stowed inside a launch vehicle fairing. These electromagnetic coils are tethered or hinged together in such a way that their motion in some directions or around some axes is constrained, as in Figure 1. Our Phase II study,awarded in Fall 2012, continued this work on electromagnetic structures, with an added focus on developing a new thermal system, investigating additional, non-structural electromagnet functions, and creating a maturation roadmap and plan for addressing barriers to feasibility of the technology. We now call the project MAGESTIC, or Magnetically Enabled STructures using Interacting Coils

Effect of Adding a Regenerator to Kornhauser's MIT "Two-Space" (Gas-Spring+Heat Exchanger) Test Rig

This study employed entropy-based second law post-processing analysis to characterize the various thermodynamic losses inside a 3-space solution domain (gas spring+heat exchanger+regenerator) operating under conditions of oscillating pressure and oscillating flow. The 3- space solution domain is adapted from the 2-space solution domain (gas spring+heat exchanger) in Kornhauser's MIT test rig by modifying the heat exchanger space to include a porous regenerator system. A thermal nonequilibrium model which assumes that the regenerator porous matrix and gas average temperatures can differ by several degrees at a given axial location and time during the cycle is employed. An important and primary objective of this study is the development and application of a thermodynamic loss post-processor to characterize the major thermodynamic losses inside the 3-space model. It is anticipated that the experience gained from thermodynamic loss analysis of the simple 3-space model can be extrapolated to more complex systems like the Stirling engine. It is hoped that successful development of loss post-processors will facilitate the improvement of the optimization capability of Stirling engine analysis codes through better understanding of the heat transfer and power losses. It is also anticipated that the incorporation of a successful thermal nonequilibrium model of the regenerator in Stirling engine CFD analysis codes, will improve our ability to accurately model Stirling regenerators relative to current multidimensional thermal-equilibrium porous media models

Cryogenics for Particle Accelerators and Detectors

Cryogenics has become a key ancillary technology of particle accelerators and detectors, contributing to their sustained development over the last fifty years. Conversely, this development has produced new challenges and markets for cryogenics, resulting in a fruitful symbiotic relation which materialized in significant technology transfer and technical progress. This began with the use of liquid hydrogen and deuterium in the targets and bubble chambers of the 1950s, 1960s and 1970s. It developed more recently with increasing amounts of liquefied noble gases - mainly argon, but also krypton and even today xenon - in calorimeters. In parallel with these applications, the availability of practical type II superconductors from the early 1960s triggered the use of superconductivity in large spectrometer magnets - mostly driven by considerations of energy savings - and the corresponding development of helium cryogenics. It is however the generalized application of superconductivity in particle accelerators - RF acceleration cavities and high-field bending and focusing magnets - which has led to the present expansion of cryogenics, with kilometer-long strings of helium-cooled devices, powerful and efficient refrigerators and superfluid helium used in high tonnage as cooling medium. This situation was well reflected over the last decades by the topical courses of the CERN Accelerator School (CAS). In 1988, CAS and DESY jointly organized the first school on Superconductivity in Particle Accelerators, held at Haus Rissen in Hamburg, where I shared the h. and duty of lecturing on cryogenics with Professor J.L. Olsen of ETH Z rich, while P. Seyfert of CEA Grenoble delivered an evening seminar on superfluidity. This successful school was reiterated in 1995, with cryogenics being addressed by Professor W.F. Vinen of University of Birmingham (superfluidity), as well as J. Schmid (thermodynamics and refrigeration) and myself (superfluid helium technology) of CERN. In the CAS School on Superconductivity and Cryogenics for Particle Accelerators and Detectors held in May 2002 in Erice, Sicily, I am particularly pleased to see a more complete syllabus in cryogenics, most of which is covered by CERN colleagues and published in this report. This is in my view, another sign of the development and vitality of this discipline at CERN, primarily in the LHC division which, by virtue of its mandate and competence, is presently building the largest helium cryogenic system in the world for the Large Hadron Collider and its experiments. I hope this report constitutes a useful source of information and updated reference for our staff dedicated to this formidable endeavour

Hydrogen Research at Florida Universities

This final report describes the R&D activities and projects conducted for NASA under the 6-year NASA Hydrogen Research at Florida Universities grant program. Contained within this report are summaries of the overall activities, one-page description of all the reports funded under this program and all of the individual reports from each of the 29 projects supported by the effort. The R&D activities cover hydrogen technologies related to production, cryogenics, sensors, storage, separation processes, fuel cells, resource assessments and education. In the span of 6 years, the NASA Hydrogen Research at Florida Universities program funded a total of 44 individual university projects, and employed more than 100 faculty and over 100 graduate research students in the six participating universities. Researchers involved in this program have filed more than 20 patents in all hydrogen technology areas and put out over 220 technical publications in the last 2 years alone. This 6 year hydrogen research program was conducted by a consortium of six Florida universities: Florida International University (FIU) in Miami, Florida State University (FSU) and Florida A&M University (FAMU) in Tallahassee, University of Central Florida (UCF) in Orlando, University of South Florida (USF) in Tampa, and University of Florida (UF) in Gainesville. The Florida Solar Energy Center (FSEC) of the University of Central Florida managed the research activities of all consortium member universities except those at the University of Florida. This report does not include any of the programs or activities conducted at the University of Florida, but can be found in NASA/CR-2008-215440-PART 1-3

ECOS 2012

The 8-volume set contains the Proceedings of the 25th ECOS 2012 International Conference, Perugia, Italy, June 26th to June 29th, 2012. ECOS is an acronym for Efficiency, Cost, Optimization and Simulation (of energy conversion systems and processes), summarizing the topics covered in ECOS: Thermodynamics, Heat and Mass Transfer, Exergy and Second Law Analysis, Process Integration and Heat Exchanger Networks, Fluid Dynamics and Power Plant Components, Fuel Cells, Simulation of Energy Conversion Systems, Renewable Energies, Thermo-Economic Analysis and Optimisation, Combustion, Chemical Reactors, Carbon Capture and Sequestration, Building/Urban/Complex Energy Systems, Water Desalination and Use of Water Resources, Energy Systems- Environmental and Sustainability Issues, System Operation/ Control/Diagnosis and Prognosis, Industrial Ecology

Energy: A continuing bibliography with indexes, supplement 16, January 1978

This bibliography lists 1287 reports, articles, and other documents introduced into the NASA scientific and technical information system from October 1, 1977 through December 31, 1977

Wind Energy Management

The book "Wind Energy Management" is a required part of pursuing research work in the field of Renewable Energy at most universities. It provides in-depth knowledge to the subject for the beginners and stimulates further interest in the topic. The salient features of this book include: - Strong coverage of key topics - User friendly and accessible presentation to make learning interesting as much as possible - Its approach is explanatory and language is lucid and communicable - Recent research papers are incorporate

Large space structures and systems in the space station era: A bibliography with indexes (supplement 05)

Bibliographies and abstracts are listed for 1363 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1991 and July 31, 1992. Topics covered include technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion and solar power satellite systems