16,909 research outputs found

    High Temperature Heat Exchanger Annual Report

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    Objectives • Identify candidate materials for heat exchanger components. • Test candidate materials for heat exchanger components. • Design critical components in the interface between the reactor and hydrogen production plant and within the sulfur iodine thermochemical process. • Fabricate prototypical components. • Test prototypical components

    Superfluid Helium Tanker (SFHT) study

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    Replenishment of superfluid helium (SFHe) offers the potential of extending the on-orbit life of observatories, satellite instruments, sensors and laboratories which operate in the 2 K temperature regime. A reference set of resupply customers was identified as representing realistic helium servicing requirements and interfaces for the first 10 years of superfluid helium tanker (SFHT) operations. These included the Space Infrared Telescope Facility (SIRTF), the Advanced X-ray Astrophysics Facility (AXAF), the Particle Astrophysics Magnet Facility (Astromag), and the Microgravity and Materials Processing Sciences Facility (MMPS)/Critical Point Phenomena Facility (CPPF). A mixed-fleet approach to SFHT utilization was considered. The tanker permits servicing from the Shuttle cargo bay, in situ when attached to the OMV and carried to the user spacecraft, and as a depot at the Space Station. A SFHT Dewar ground servicing concept was developed which uses a dedicated ground cooling heat exchanger to convert all the liquid, after initial fill as normal fluid, to superfluid for launch. This concept permits the tanker to be filled to a near full condition, and then cooled without any loss of fluid. The final load condition can be saturated superfluid with any desired ullage volume, or the tank can be totally filed and pressurized. The SFHT Dewar and helium plumbing system design has sufficient component redundancy to meet fail-operational, fail-safe requirements, and is designed structurally to meet a 50 mission life usage requirement. Technology development recommendations were made for the selected SFHT concept, and a Program Plan and cost estimate prepared for a phase C/D program spanning 72 months from initiation through first launch in 1997

    JT8D and JT9D jet engine performance improvement program. Task 1: Feasibility analysis

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    JT8D and JT9D component performance improvement concepts which have a high probability of incorporation into production engines were identified and ranked. An evaluation method based on airline payback period was developed for the purpose of identifying the most promising concepts. The method used available test data and analytical models along with conceptual/preliminary designs to predict the performance improvements, weight, installation characteristics, cost for new production and retrofit, maintenance cost, and qualitative characteristics of candidate concepts. These results were used to arrive at the concept payback period, which is the time required for an airline to recover the investment cost of concept implementation

    ONLINE APPROXIMATION ASSISTED MULTIOBJECTIVE OPTIMIZATION WITH HEAT EXCHANGER DESIGN APPLICATIONS

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    Computer simulations can be intensive as is the case in Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). The computational cost can become prohibitive when using these simulations with multiobjective design optimization. One way to address this issue is to replace a computationally intensive simulation by an approximation which allows for a quick evaluation of a large number of design alternatives as needed by an optimizer. This dissertation proposes an approach for multiobjective design optimization when combined with computationally expensive simulations for heat exchanger design problems. The research is performed along four research directions. These are: (1) a new Online Approximation Assisted Multiobjective Optimization (OAAMO) approach with a focus on the expected optimum region, (2) a new approximation assisted multiobjective optimization with global and local metamodeling that always produces feasible solutions, (3) a framework that integrates OAAMO with multiscale simulations (OAAMOMS) for design of heat exchangers at the segment and heat exchanger levels, and (4) applications of OAAMO combined with CFD for shape design of a header for a new generation of heat exchangers using Non-Uniform Rational B-Splines (NURBS). The approaches developed in this thesis are also applied to optimize a coldplate used in electronic cooling devices and different types of plate heat exchangers. In addition many numerical test problems are solved by the proposed methods. The results of these studies show that the proposed online approximation assisted multiobjective optimization is an efficient approach that can be used to predict optimum solutions for a wide class of problems including heat exchanger design problems while reducing significantly the computational cost when compared with existing methods

    On the Road to a Unified Market for Energy Efficiency: The Contribution of White Certificates Schemes

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    White certificates schemes mandate competing energy companies to promote energy efficiency with flexibility mechanisms, including the trading of energy savings. So far, stylized facts are lacking and outcomes are mainly country-specific. By comparing results of British, Italian and French experiences, we attempt to identify the core determinants of their performances. We show that (i) white certificates schemes are depicted in theoretical works as mandatory subsidies on energy efficiency goods recovered by an end-use energy tax, whereby white certificates exchanges are not a central feature; (ii) at current stages, existing schemes are cost-effective and economically efficient, with large discrepancies though; (iii) the hybrid subsidy-tax mechanism seems valid but conditional to cost pass through permissions; otherwise, obliged energy companies merely promote information on the “downstream” side (i.e. at the consumer level); (iv) although white certificates exchange between different types of actors involved can be important as in Italy, trade among obliged companies is negligible; instead, flexibility sustains vertical relationships between obliged parties and “upstream” partners (i.e. installers, energy service companies). In this respect, we support the view that white certificates schemes are a policy instrument of multi-functional nature (subsidisation, information, technology diffusion), whose static and dynamic efficiency depends upon the consistency between a proper definition of long-term energy savings, the appropriate cost-recovery permission and a fine coordination with other instruments. We finally propose a four stages deployment pattern, along which fragmented markets for energy efficient technologies get closer to create a unified market delivering energy efficiency as a homogeneous good.White Certificates Schemes, Static Efficiency, Dynamic Efficiency, Vertical Organisation, Policy Coordination

    Development of advanced fuel cell system, phase 2

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    A multiple task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. Development and characterization of a very stable gold alloy catalyst was continued from Phase I of the program. A polymer material for fabrication of cell structural components was identified and its long term compatibility with the fuel cell environment was demonstrated in cell tests. Full scale partial cell stacks, with advanced design closed cycle evaporative coolers, were tested. The characteristics demonstrated in these tests verified the feasibility of developing the engineering model system concept into an advanced lightweight long life powerplant

    Social fund support of microfinance : a review of implementation experience

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    The case studies were developed in order to help Bank task team leaders, and their client country counterparts, design and support effective microfinance components, within social funds. The case studies aim to highlight best practice, as well as challenges for designing, and implementing a microfinance component within a multi-sectoral project. Based on lessons learned from these case studies, a set of guidelines were developed, available from the Social Protection Advisory Service, or the Social Funds website.Banks&Banking Reform,Rural Finance,Private Participation in Infrastructure,Agricultural Research,Microfinance
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