A new approach for thermal performance calculation of cross-flow heat exchangers

A new numerical methodology for thermal performance calculation in cross-flow heat exchangers is developed. Effectiveness-number of transfer units (epsilon-NTU) data for several standard and complex flow arrangements are obtained using this methodology. The results are validated through comparison with analytical solutions for one-pass cross-flow heat exchangers with one to four rows and with approximate series solution for an unmixed-unmixed heat exchanger, obtaining in all cases very small errors. New effectiveness data for some complex configurations are provided. (c) 2005 Elsevier Ltd. All rights reserved.

Keskinopeusalueella toimivan induktiomoottori - puhallinkäytön suorituskyvyn mittaus alipainekäytössä

Keskinopeusalueella toimivaa massiiviroottorista epätahtimoottoria voidaan käyttää teollisissa puhaltimissa, joissa on tärkeää saavuttaa normaalia korkeampi pyörimisnopeus ja paine-ero. Usein tällaisella puhaltimella saavutetaan parempi hyötysuhde ja säädettävyys kuin vanhoilla volumetrisilla pumpuilla. Paperikoneiden vedenpoistossa käytetty alipaineen tuotto muodostaa erään sovelluskohteen tällaiselle puhallinkäytölle. Työssä esitellään tällaiseen sovelluskohteeseen suunnitellun puhaltimen ja sitä käyttävän massiiviroottorisen epätahtikoneen testausmenetelmät niiden ominaisuuksien määrittämiseksi, sekä siihen tarvittavan mittalaitteiston vaatimukset. Puhaltimen osalta esitetään täydellinen laskenta perustuen LTKK:ssa 20.10.2000 - 27.10.2000 välisenä aikana suoritettuun puhaltimen testiajoon.

Ydinvoimalaitoksen höyryturbiinin suorituskyvyn laskenta

Diplomityön tavoitteena on selvittää Loviisan ydinvoimalaitoksen höyryturbiinin hyötysuhteen parantamismahdollisuuksia. Työn kuvaan liittyvät oleellisesti höyryturbiinin siipivyöhykkeiden nopeuskolmioiden sekä hyötysuhteiden laskenta. Höyryturbiinien kehityskaarta sekä turbiinin häviökerrointen laskentayhtälöitä on esitetty useasta eri lähteestä ja vuosikymmeniltä. Työssä selvitettiin uusimpia ydinvoimalaitosten kostea höyryturbiinien suunnitteluperusteita lukuisista eri lähteistä. Kaikkien lähteiden mukaan kostean höyryn alueella tapahtuvaa paisuntaa on haasteellista mallintaa. Työssä on esitelty artikkeleissa tulleita eri näkökulmia höyryturbiinien suorituskyvyn parantamiseksi, sekä rakenteellisia että laskennallisia. Työssä esitellään monia turbiinin virtauksen ja suorituskyvyn laskentamenetelmiä. Esimerkiksi Baumannin säännön laskenta on yksinkertainen tapa käsitellä turbiinin suorituskykyä kostean höyryn alueella. Keskeisimpiä tehtyjä havaintoja oli se, että korkeapaineturbiinin ensimmäisestä vaiheesta löytyi mahdollista parannuspotentiaalia Loviisaan ydinvoimalaitoksen tehon lisäämiseksi. Ensimmäisessä vaiheessa on oletettu siipien olevan Laval –tyyppisiä, mutta käytännössä näin ei ole. Korkeapaineturbiinin nykyisen turbosuuttimen toimintaa voitaisiin tehostaa. Lisäksi Loviisan matalapaineturbiinin viimeisen siipivaiheen jälkeen aiheutuu suuret ulosvirtaushäviöt. Osa suurinopeuksisen virtauksen energiasta pystyttäisiin kuitenkin hyödyntämään vielä ulosvirtauskanavassa olevalla diffuusorilla.

Comparison of Different Concentrated Solar Power Collector Designs and Development of a Linear Fresnel Solar Collector Model

Concentrated solar power (CSP) is a renewable energy technology, which could contribute to overcoming global problems related to pollution emissions and increasing energy demand. CSP utilizes solar irradiation, which is a variable source of energy. In order to utilize CSP technology in energy production and reliably operate a solar field including thermal energy storage system, dynamic simulation tools are needed in order to study the dynamics of the solar field, to optimize production and develop control systems. The object of this Master’s Thesis is to compare different concentrated solar power technologies and configure a dynamic solar field model of one selected CSP field design in the dynamic simulation program Apros, owned by VTT and Fortum. The configured model is based on German Novatec Solar’s linear Fresnel reflector design. Solar collector components including dimensions and performance calculation were developed, as well as a simple solar field control system. The preliminary simulation results of two simulation cases under clear sky conditions were good; the desired and stable superheated steam conditions were maintained in both cases, while, as expected, the amount of steam produced was reduced in the case having lower irradiation conditions. As a result of the model development process, it can be concluded, that the configured model is working successfully and that Apros is a very capable and flexible tool for configuring new solar field models and control systems and simulating solar field dynamic behaviour.

Capital investments planning and life cycle simulations for the new valves manufacturing facility in Russia

The focus of the research is on the derivation of the valid and reliable performance results regarding establishment and launching of the new full-scale industrial facility, considering the overall current conditions for the project realization in and out of Russia. The study demonstrates the process of the new facility concept development, with following perfor-mance calculation, comparative analyzes conduction, life-cycle simulations, performance indicators derivation and project`s sustainability evaluation. To unite and process the entire input parameters complexity, regards the interlacing between the project`s internal technical and commercial sides on the one hand, and consider all the specifics of the Russian conditions for doing business on the other hand, was developed the unique model for the project`s performance calculation, simulations and results representation. The complete research incorporates all corresponding data to substantiate the assigned facility`s design, sizing and output capacity for high quality and cost efficient ferrous pipe-line accessories manufacturing, as well as, demonstrates that this project could be suc-cessfully realized in current conditions in Russia and highlights the room for significant performance and sustainability improvements based on the indexes of the derived KPIs.

Performance of GEANT4 in dosimetry applications: Calculation of X-ray spectra and kerma-to-dose equivalent conversion coefficients

In order to validate the Geant4 toolkit for dosimetry applications, simulations were performed to calculate conversion coefficients h(10, alpha) from air kerma free-in-air to personal dose equivalent Hp(10, a). The simulations consisted of two parts: the production of X-rays with radiation qualities of narrow and wide spectra, and the interaction of radiation with ICRU tissue-equivalent and ISO water slab phantoms. The half-value layers of the X-ray spectra obtained by simulation were compared with experimental results. Mean energy, spectral resolution, half-value layers and conversion coefficients were compared with ISO reference values. The good agreement between results from simulation and reference data shows that the Geant4 is suitable for dosimetry applications which involve photons with energies in the range of ten to a few hundreds of keV. (C) 2008 Elsevier Ltd. All rights reserved.

Análise do desempenho muscular do quadríceps e dos isquiotibiais em função da série temporal e da amplitude de movimento de atletas amadoras de futsal feminino = : Analysis of muscle performance of the quadriceps and hamstrings as a function of the times series and range of motion of amateurfemale futsal athletes

Universidade Estadual de Campinas . Faculdade de Educação Física

Vegetable Oil Quenchants: Calculation and Comparison of The Cooling Properties of a Series of Vegetable Oils

The compositions of canola, soybean, corn, cottonseed and sunflower oils suggest that they exhibit substantially different propensity for oxidation following the order of Canola < corn < cottonseed < sunflower approximate to soybean. These data suggest that any of the vegetable oils evaluated could be blended with minimal impact on viscosity although compositional differences would surely affect oxidative stability. Cooling curve analysis showed that similar cooling profiles were obtained for different vegetable oils. Interestingly, no film boiling or transition nucleate boiling was observed with any of the vegetable oils and heat transfer occurs only by pure nucleate boiling and convection. High-temperature cooling properties of vegetable oils are considerable faster than those observed for petroleum oil-based quenchants. (C)2010 Journal of Mechanical Engineering. All rights reserved.

Power Factor Calculation by the Finite Element Method

The use of finite element analysis (FEA) to design electrical motors has increased significantly in the past few years due the increasingly better performance of modern computers. Even though the analytical software remains the most used tool, the FEA is widely used to refine the analysis and gives the final design to be prototyped. The power factor, a standard data of motor manufactures data sheet is important because it shows how much reactive power is consumed by the motor. This data becomes important when the motor is connected to network. However, the calculation of power factor is not an easy task. Due to the saturation phenomena the input motor current has a high level of harmonics that cannot be neglected. In this work the FEA is used to evaluate a proposed (not limitative) methodology to estimate the power factor or displacement factor of a small single-phase induction motor. Results of simulations and test are compared.

A comparison of two methods for the calculation of accumulated oxygen deficit

The aim of this study was to compare accumulated oxygen deficit data derived using two different exercise protocols with the aim of producing a less time-consuming test specifically for use with athletes. Six road and four track male endurance cyclists performed two series of cycle ergometer tests. The first series involved five 10 min sub-maximal cycle exercise bouts, a (V) over dotO(2peak) test and a 115% (V) over dotO(2peak) test. Data from these tests were used to estimate the accumulated oxygen deficit according to the calculations of Medbo et al. (1988). In the second series of tests, participants performed a 15 min incremental cycle ergometer test followed, 2 min later, by a 2 min variable resistance test in which they completed as much work as possible while pedalling at a constant rate. Analysis revealed that the accumulated oxygen deficit calculated from the first series of tests was higher (P< 0.02) than that calculated from the second series: 52.3 +/- 11.7 and 43.9 +/- 6.4 ml . kg(-1), respectively (mean +/- s). Other significant differences between the two protocols were observed for (V) over dot O-2peak, total work and maximal heart rate; all were higher during the modified protocol (P

Digital radiography detector performance

The characterization of physical properties of digital imaging systems requires the determination and measurement of detectors’ physical performance. Those measures such as modulation transfer function (MTF), noise power spectra (NPS), and detective quantum efficiency (DQE) provide objective evaluations of digital detectors’ performance. To provide an MTF, NPS, and DQE calculation from raw-data images it is necessary to implement a method that is undertaken by two major steps: (1) image acquisition and (2) quantitative measure determination method. In this chapter a comprehensive description about a method to provide the measure of performance of digital radiography detectors is provided.

Many-core approach to 2D-DCT calculation using an FPGA

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia de Electrónica e Telecomunicações

Exploiting sensor redundancy for the calculation of fractional derivatives in the presence of noise

In this paper a new method for the calculation of the fractional expressions in the presence of sensor redundancy and noise, is presented. An algorithm, taking advantage of the signal characteristics and the sensor redundancy, is tuned and optimized through genetic algorithms. The results demonstrate the good performance for different types of expressions and distinct levels of noise.

Practical software improve design and performance of a randomly packed air stripping column for removing volatile organic compounds from water

STRIPPING is a software application developed for the automatic design of a randomly packing column where the transfer of volatile organic compounds (VOCs) from water to air can be performed and to simulate it’s behaviour in a steady-state. This software completely purges any need of experimental work for the selection of diameter of the column, and allows a choice, a priori, of the most convenient hydraulic regime for this type of operation. It also allows the operator to choose the model used for the calculation of some parameters, namely between the Eckert/Robbins model and the Billet model for estimating the pressure drop of the gaseous phase, and between the Billet and Onda/Djebbar’s models for the mass transfer. Illustrations of the graphical interface offered are presented.

A gestão do risco em instituições bancárias: uma análise com recurso a medidas de avaliação da performance ajustadas ao risco

Dissertação de Mestrado apresentado ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Auditoria sob orientação do Mestre Carlos Mota