Preliminary Performance Estimates Research Articles

A novel sustainable cooling system in a tunnel with high geotemperature: Concept and thermal performance

An increasing number of tunnels pass through the anomaly geothermal zones and inevitably encounter thermal engineering geological problems during tunnel operation. In order to efficiently eliminate the thermal damage, an efficient and energy-saving cooling system composed of borehole heat exchangers (BHEs) and thermal insulation layer in a high geotemperature tunnel is proposed. Taking Sangzhuling tunnel as an example, a 3D numerical model is established for analyzing the thermal performance of the cooling system, and is validated by the field measured data. The cooling effect of the cooling system in the high-geotemperature tunnels is proved to be remarkable in comparison with the tunnel having thermal insulation layer. Moreover, the effects of design parameters on the thermal performance are revealed during a 180-day heat extraction. The results show that a lower inlet temperature contributes to a shorter drop to the target tunnel ambient temperature. The effect of the cooling system is significantly improved as the borehole depth increases within a limited extent because the cooling effect cannot be infinitely improved by increasing the borehole depth. The thermal insulation layer plays a beneficial role in reducing the maximum ambient temperature and an adverse effect on the temperature reduction rate. These findings contribute to preliminary thermal performance estimation of the BHE cooling system in high-geotemperature tunnels without large-scale simulation.

Designing nano-aluminum laden fuel pump for aviation applications

In view of the fact that traditional liquid propellants cannot meet the design requirements of large-thrust flight vehicle, it has become a new trend to add nano-metal powder to liquid propellants to greatly increase density and specific impulse. In order to achieve the variable flow-rate and variable-proportion transportation of aviation fuel with nano-aluminum, a new type of solid-liquid mixing pumping system is designed, including powder conveying device, stirring device, pump and corresponding drive and transmission system. For the purpose of avoiding the frictional contact between the rotors, which will bring potential hazard to nano-aluminum powder, a non-contact twin-screw pump with synchronous gears is designed. Among them, based on the considerations of flow pulsation, volumetric efficiency and manufacturing difficulty, cycloid profile is adopted for screw rotors. After completing the functional design, geometric parameter design, structural design, 3D modeling, prototype manufacturing and preliminary performance estimation of the mixing pumping system, the performance of the screw feeder, agitator, screw pump was tested through experiments to meet the expected design requirements. The designed agitator can achieve sufficient mixing at 500 rpm in less than 10 s. Even though 50-micron clearances are designed with a relatively small rotor diameter, the volumetric efficiency of screw pump can reach above 50% when the discharge pressure is below 450 kPa and the flow rate is set as 10 L/min, the power of the screw pump is less than 700 W. This design facilitates the rapid real-time preparation of metallized propellants and provides a reference for further improving the design and control methods of nanoparticle two-phase flow pumping.

CFD based evaluation of conventional electrical submersible pump for high-speed application

Fluctuations in oil prices have negatively affected the petroleum industry, prompting to look for innovative ways to optimize oil recovery. One of the current approaches to optimize oil production is to employ high-speed ESPs with Permanent Magnet Motors (PMM) that allow reducing the pump size while increasing the operating envelop. Standard affinity laws are a useful tool to provide a preliminary estimate of common pump performance. However, there is a need to understand the detailed variation in the flow variables and losses incurring due to fluid-geometry interactions at high rotational speeds. To evaluate the hydraulic performance of a mixed flow pump, Computational Fluid Dynamics (CFD) simulations were performed at rotational speeds ranging from 3600 rpm to 20000 rpm using fluids with different viscosities. Fluid behavior is studied by observing the change in flow parameters with rotational speed. Similitude analysis is utilized to characterize the pump performance. The numerical results yielded improved pump hydraulic performance with an increase in rotational speeds which is attributed to reduced separation losses mainly in the diffuser section. Research is concluded with further evaluation of the complete stage including secondary leakage flow path on flow variables and axial thrust forces.

A design methodology for soft-core platforms on FPGA with SMP Linux, OpenMP support, and distributed hardware profiling system

In recent years, the use of multiprocessor systems has become increasingly common. Even in the embedded domain, the development of platforms based on multiprocessor systems or the porting of legacy single-core applications are frequent needs. However, such designs are often complicated, as embedded systems are characterized by numerous non-functional requirements and a tight hardware/software integration. This work proposes a methodology for the development and validation of an embedded multiprocessor system. Specifically, the proposed method assumes the use of a portable, open source API to support the parallelization and the possibility of prototyping the system on a field-programmable gate array. On this basis, the proposed flow allows an early exploration of the hardware configuration space, a preliminary estimate of performance, and the rapid development of a system able to satisfy the design specifications. An accurate assessment of the actual performance of the system is then enforced by the use of an hardware-based profiling subsystem. The proposed design flow is described, and a version specifically designed for LEON3 processor is presented and validated. The application of the proposed methodology in a real case of industrial study is then presented and analyzed.

Polygeneration using agricultural waste: Thermodynamic and economic feasibility study

Agricultural wastes vary widely in composition. Presently, these are either of no use or remain under-utilized in absence of available technology. Many of these have useful calorific values and can be used more efficiently with the development of suitable technology. Availability of these also varies widely in places and over the year. Polygeneration is the delivery of multiple utility outputs efficiently from a single unit through proper system integration. Combining suitable utility outputs with local agricultural wastes as inputs to polygeneration can be efficient future sustainable solution for rural people. Preliminary feasibility and performance estimation using thermodynamic model in Aspen Plus® for such polygeneration with electricity, refrigeration, utility heat and ethanol as outputs is reported in this paper. Also economic feasibility of the polygeneration plant is reported in this paper. Rice straw, sugarcane bagasse and coconut fiber dust are three typical different agricultural wastes and are considered as inputs. Results show that such polygeneration is highly promising as decentralized efficient option, specifically for rural people.

THE LARGE HADRON COLLIDER 2008–2013

The Large Hadron Collider (LHC) was first suggested (in a documented way) in 1983 (S. Myers and W. Schnell, Preliminary performance estimates for a LEP proton collider, LEP Note 440, April 1983) as a possible future hadron collider to be installed in the 27 km "LEP" tunnel. More than 30 years later the collider has been operated successfully with beam for three years with spectacular performance and has discovered the long-sought-after Higgs boson. The LHC is the world's largest and most energetic particle collider. It took many years to plan and build this large complex machine which promises exciting, new physics results for many years to come. I describe the LHC design objectives, review some of the more relevant beam effects, define the major accelerator components and parameters, and finally give an overview of the commissioning and operational performance since the initial turn on of the collider. The latter will include the major accident which took place in September 2008 and the subsequent repair and redesign of the faulty components. The first attempt to circulate beam in the LHC in September 2008 were initially very successful. However, after only nine days of preliminary beam commissioning, on 19 September 2008, disaster struck: the last octant was being ramped up in preparation for high energy operation when a magnet interconnect failed and the enormous energy stored in the superconducting magnets was released in an uncontrolled way and damaged around 600 m of the LHC installed equipment. The next 14 months were crucial for the machine. A crash programme for the repair of the damaged sector was initiated as well as in depth studies to understand the cause of the failure and make design changes which would ensure that such an accident could never reoccur in the future. In this paper, the story of the four years of the intensive activity since the accident is described starting with the repair of the damaged area and followed by the three very successful years of beam operation.

Early termination of a two‐stage study to develop and validate a panel of biomarkers

Two-stage designs to develop and validate a panel of biomarkers present a natural setting for the inclusion of stopping rules for futility in the event of poor preliminary estimates of performance. We consider the design of a two-stage study to develop and validate a panel of biomarkers where a predictive model is developed using a subset of the samples in stage 1 and the model is validated using the remainder of the samples in stage 2. First, we illustrate how we can implement a stopping rule for futility in a standard, two-stage study for developing and validating a predictive model where samples are separated into a training sample and a validation sample. Simulation results indicate that our design has type I error rate and power similar to the fixed-sample design but with a substantially reduced sample size under the null hypothesis. We then illustrate how we can include additional interim analyses in stage 2 by applying existing group sequential methodology, which results in even greater savings in the number of samples required under both the null and the alternative hypotheses. Our simulation results also illustrate that the operating characteristics of our design are robust to changes in the underlying marker distribution.

Propulsive Performance of Ideal Detonation Turbine Based Combined Cycle Engine

A novel two-mode propulsion system based on detonation combustion, known as a detonation turbine based combined cycle engine (DTBCC), was proposed and thermodynamically analyzed for potential application to aircrafts whose flight Mach number is from 0 to 5. The obvious advantage of the two-mode system is that both modes share the same multidetonation chambers. The quasi-stable total temperature and total pressure for inlet conditions of the turbine could be realized in this hybrid pulse detonation engine. A key parameter (drive area ratio) was defined as the ratio of the outflow area at the head to the cross-sectional area of the detonation chamber. The calculated results showed that the increase of the drive area ratio led to the increase in the mass flow entering the turbine; however, this led to the decrease of the total inlet temperature, the total inlet pressure, and the expansion-pressure ratio of the turbine. Compared with an ideal turbojet engine, the inlet temperature of the turbine in a preturbine hybrid pulse detonation engine with a drive area ratio of 1 was 80 K lower than the former under the same pressure ratio and the same fuel-air ratio. In other words, the increase of the drive area ratio may improve the performance of this hybrid pulse detonation engine. Variation of the pressure ratio was adapted to varied flight Mach numbers by a change of the drive area ratio, which induced the enlargement of the operating range. Finally, a performance model was established to research the components’ characteristics and the propulsive performance of the engine. Preliminary performance estimates suggested that thrust and specific fuel consumption of the two-mode propulsion system were superior to the existing turbine based combined cycle designs.

Preliminary Design and Performance Estimation of Radial Inflow Turbines: An Automated Approach

A comprehensive one-dimensional meanline design approach for radial inflow turbines is described in the present work. An original code was developed in Python that takes a novel approach to the automatic selection of feasible machines based on pre-defined performance or geometry characteristics for a given application. It comprises a brute-force search algorithm that traverses the entire search space based on key non-dimensional parameters and rotational speed. In this study, an in-depth analysis and subsequent implementation of relevant loss models as well as selection criteria for radial inflow turbines is addressed. Comparison with previously published designs, as well as other available codes, showed good agreement. Sample (real and theoretical) test cases were trialed and results showed good agreement when compared to other available codes. The presented approach was found to be valid and the model was found to be a useful tool with regards to the preliminary design and performance estimation of radial inflow turbines, enabling its integration with other thermodynamic cycle analysis and three-dimensional blade design codes.

MicroRadarNet: A network of weather micro radars for the identification of local high resolution precipitation patterns

In this paper, MicroRadarNet, a novel micro radar network for continuous, unattended meteorological monitoring is presented. Key aspects and constraints are introduced. Specific design strategies are highlighted, leading to the technological implementations of this wireless, low-cost, low power consumption sensor network.Raw spatial and temporal datasets are processed on-board in real-time, featuring a consistent evaluation of the signals from the sensors and optimizing the data loads to be transmitted. Network servers perform the final post-elaboration steps on the data streams coming from each unit. Final network products are meteorological mappings of weather events, monitored with high spatial and temporal resolution, and lastly served to the end user through any Web browser.This networked approach is shown to imply a sensible reduction of the overall operational costs, including management and maintenance aspects, if compared to the traditional long range monitoring strategy.Adoption of the TITAN storm identification and nowcasting engine is also here evaluated for in-loop integration within the MicroRadarNet data processing chain. A brief description of the engine workflow is provided, to present preliminary feasibility results and performance estimates. The outcomes were not so predictable, taking into account relevant operational differences between a Western Alps micro radar scenario and the long range radar context in the Denver region of Colorado. Finally, positive results from a set of case studies are discussed, motivating further refinements and integration activities.

Preliminary Estimate of Triphasic CT Enterography Performance in Hemodynamically Stable Patients With Suspected Gastrointestinal Bleeding

The objective of our study was to retrospectively evaluate the performance of triphasic CT enterography and identify causes of false-negative CT results in hemodynamically stable patients with suspected gastrointestinal bleeding. A retrospective review of 48 patients (male-female ratio, 22:26) with suspected gastrointestinal bleeding (first-episode gastrointestinal bleed, n = 19; obscure gastrointestinal bleed, n = 29) who underwent triphasic CT enterography was performed. All patients had endoscopic, pathologic, or other imaging confirmation within 3 months of triphasic CT enterography. The sensitivity and specificity of triphasic CT enterography were calculated using pathology, endoscopy, or other imaging confirmation as the reference standard. Results were retrospectively reviewed to determine the cause of missed findings at triphasic CT enterography. The overall sensitivity and specificity of triphasic CT enterography for detecting gastrointestinal bleeding was 33% (7/21) and 89% (24/27), respectively. Sensitivity and specificity were higher in first-episode gastrointestinal bleed cases (42% and 100%, respectively) than in obscure gastrointestinal bleed cases (22% and 85%). In the subset of patients undergoing capsule endoscopy (n = 17), only triphasic CT enterography identified two of three bleeding sources. Triphasic CT enterography did not identify six ulcers, four vascular malformations, two hemorrhoids, a duodenal mass, and a bleeding colonic diverticulum. The missed findings at triphasic CT enterography were attributed to being CT occult (n = 9), perception errors (n = 4), and technical errors (n = 1). If perception errors are excluded, the sensitivity of triphasic CT enterography increases to 52% (11/21). Triphasic CT enterography can be a useful and complementary test in the evaluation of clinically stable patients with suspected gastrointestinal bleeding by identifying the bleeding source in one third to one half of patients. Because of the potential for perception errors, radiologists should familiarize themselves with the appearance of bleeding sources at CT enterography.

Status of the LIGO-AURIGA Joint Burst Analysis

The recently upgraded AURIGA detector and the LIGO observatory were simultaneously acquiring data for the first time in a 2-weeks period during the LIGO S3 run. This coincidence run motivated a collaborative effort to test search methods for gravitational wave bursts on real data. The adopted method uses broad-band cross correlation for the LIGO interferometers triggered by AURIGA events in the 850-950 Hz band. This paper describes the analysis technique and gives a status report on the search, with emphasis on the tuning procedure. Preliminary network performance and background estimates will be provided.

Preliminary estimates of performance and cost of mercury emission control technology applications on electric utility boilers: An update

AbstractThe Environmental Protection Agency has recently proposed a reduction in mercury emissions from coal‐fired power plants. There are two broad approaches under development to controlling mercury emissions from coal‐fired electric utility boilers: (1) powdered activated carbon (PAC) injection; and (2) multipollutant control, in which Hg capture is enhanced in existing and new sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter (PM) control devices. To help inform the recent EPA rulemaking proposal, estimates of performance levels and related costs associated with the above mercury control approaches were developed. This work presents these estimates.Estimates of cost for PAC injection range from 0.003 to 3.096 mills/kWh. In general, the higher costs are associated with the plants using spray dryers and electrostatic precipitators (ESPs) or plants using hot‐side ESPs, which represent a minority of power plants. Excluding these plants, cost estimates range between 0.003 and 1.903 mills/kWh. At the low end of the cost ranges, 0.003 mills/kWh, it is assumed that no additional control technologies are needed, but mercury monitoring will be necessary. In these cases, high mercury removal may be the result of the type of NOx and SO2 control measures currently used, such as combinations of selective catalytic reduction and wet flue gas desulfurization or spray drier absorbers with fabric filters on bituminous coal–fired boilers.Because mercury control approaches are under development at present, cost and performance estimates are preliminary and are expected to be refined as mercury control technologies are matured to commercial status. Factors that may affect the performance of these technologies include speciation of mercury in flue gas, the characteristics of the sorbent, and the type(s) of PM, NOx, and SO2 controls used. The effect of these factors may not be entirely accounted for in the data points that form the basis for this work. Ongoing research is expected to address these issues. © 2004 American Institute of Chemical Engineers Environ Prog, 2005

Effects of atmospheric turbulence on the GENIE nulling interferometer

Two competitive design studies for the Ground-based European Nulling Interferometer Experiment (GENIE) have recently been initiated by the European Space Agency and the European Southern Observatory. A major issue in these studies is the influence of atmospheric turbulence on the performance of the instrument, and how atmospheric effects can be compensated in order to reach the goal performance (detection of faint exozodiacal clouds). In this paper, we review the main atmospheric processes affecting a nulling interferometer and discuss possible ways to reduce them by means of real-time control systems. Preliminary performance estimates of GENIE are then presented. The effects of the thermal background and its fluctuations (Absil & Bakker 2004) are not considered here.

Coupled Conduction and Intermittent Convective Heat Transfer from a Buried Pipe

An accurate estimate of the heat transfer from a buried pipe to the surrounding ground is essential for the design of the ground-loop portion of a ground-source heat pump. Exact analytical solutions to this problem are complicated by the fact that heat pump systems rarely operate continuously. Complete numerical simulations of system designs can be carried out, but these are unwieldy and difficult to justify for initial scoping calculations, or for preliminary performance estimates. The purpose of this article is to provide insight into the heat transfer mechanisms and to describe the development of simple algebraic correlations that can be used to approximate the intermittent overall heat transfer between a fluid flowing in an isolated buried pipe and the surrounding ground. The correlations described in this article were drawn from results of a numerical finite-difference analysis of a fluid flowing intermittently in a single round pipe and exchanging heat with the surrounding ground. It is found that the cycle average heat transfer is always lower for the intermittent case than for the continuous case, but that the average over just the active part of the cycle is always higher for any intermittent case than for the continuous case. The effect of the ground thermal diffusivity is largest when the heat transfer coefficient is large, and decreases with decreasing heat transfer coefficient. The range of heat transfer coefficients where isothermal wall conditions are approached is illustrated. Correlations for the operating average and cycle average total heat transfer are presented as functions of the thermal diffusivity, intermittence factor, and heat transfer coefficient.

Preliminary Estimates of Performance and Cost of Mercury Control Technology Applications on Electric Utility Boilers

ABSTRACT Under the Clean Air Act Amendments of 1990, the U.S. Environmental Protection Agency (EPA) determined that regulation of mercury emissions from coal-fired power plants is appropriate and necessary. To aid in this determination, preliminary estimates of the performance and cost of powdered activated carbon (PAC) injection-based mercury control technologies were developed. This paper presents these estimates and develops projections of costs for future applications. Cost estimates were developed using PAC to achieve a minimum of 80% mercury removal at plants using electrostatic precipitators and a minimum of 90% removal at plants using fabric filters. These estimates ranged from 0.305 to 3.783 mills/kWh. However, the higher costs were associated with a minority of plants using hot-side electrostatic precipitators (HESPs). If these costs are excluded, the estimates range from 0.305 to 1.915 mills/kWh. Cost projections developed using a composite lime-PAC sor-bent for mercury removal ranged from 0.183 to 2.270 mills/kWh, with the higher costs being associated with a minority of plants that used HESPs.

Preliminary Estimates of Performance and Cost of Mercury Control Technology Applications on Electric Utility Boilers

ABSTRACT Under the Clean Air Act Amendments of 1990, the U.S. Environmental Protection Agency (EPA) determined that regulation of mercury emissions from coal-fired power plants is appropriate and necessary. To aid in this determination, preliminary estimates of the performance and cost of powdered activated carbon (PAC) injection-based mercury control technologies were developed. This paper presents these estimates and develops projections of costs for future applications. Cost estimates were developed using PAC to achieve a minimum of 80% mercury removal at plants using electrostatic precipitators and a minimum of 90% removal at plants using fabric filters. These estimates ranged from 0.305 to 3.783 mills/kWh. However, the higher costs were associated with a minority of plants using hot-side electrostatic precipitators (HESPs). If these costs are excluded, the estimates range from 0.305 to 1.915 mills/kWh. Cost projections developed using a composite lime-PAC sorbent for mercury removal ranged from 0.183 to 2.270 mills/kWh, with the higher costs being associated with a minority of plants that used HESPs.

Sizing windows to achieve passive cooling, passive heating, and daylighting in hot arid regions

The study aims to demonstrate a process for sizing the windows of a passive solar house case study that involves a multi-decision problem. The initial design was created in an earlier stage, during which, decisions on broader issues such as building orientation, form design, and the appropriate spatial organization of the building were made. It applies a variety of methods to generate and evaluate design alternatives such as rules of thumb and LCR method for passive heating; earth cooling and cross ventilation rules of thumb for passive cooling; and dylighting factor for daylighting. At the end, the study makes preliminary performance estimates between two alternatives to choose a final solution.

Optimal design of advanced power systems under uncertainty

Technical and economic uncertainties are not rigorously treated or characterized in most preliminary cost and performance estimates of advanced power system designs. Nor do current design methods rigorously address the issues of design under uncertainty. However, process costs and other important quality measures, such as controllability, safety, and environmental compliance, largely depend on the process synthesis stage. This conceptual design stage involves identifying the basic flowsheet structures from a typically large number of alternatives. This paper describes recent developments in on-going research to develop and demonstrate advanced computer-based methods for dealing with uncertainties that are critical to the design of advanced coal-based power systems. Results are presented illustrating the use of these new modeling tools for the environmental control design of an advanced energy system based on an integrated gasification combined cycle (IGCC) for electric power generation.

Precision time-transfer in transport networks using digital cross-connect systems

A technique for precise synchronization of the time-of-day clocks in networks of digital cross-connect systems (DCSs) is described. This method is intended to enhance the performance of reconfigurable transport networks and is specifically devised to exploit the fine time resolution of the carrier signals to which a DCS has direct access. The resulting scheme is a master-slave, multisite, implicitly delay compensated, nonhierarchical time-transfer method with a theoretical precision of one bit time at the carrier rate. In practice, precision is limited by transmission span delay asymmetries but residual time errors of under 1 mu s are predicted. The method is intended for n/n space-switching DCS, but other DCS properties can be accommodated. Requirements for DCS equipment design are given, including a generic circuit module for DCS hardware support of the time transfer function. The proposed method applies to DS-3 networks or synchronous optical networks and requires no change in the standards. Measurement or improved estimation of characteristic span delay asymmetries is recommended to refine the preliminary performance estimate.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>