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Статті в журналах з теми "Direct heat meter"
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Magonski, Zbigniew. "Combustion Heat Meter." Journal of Microelectronics and Electronic Packaging 14, no. 3 (July 1, 2017): 100–107. http://dx.doi.org/10.4071/imaps.0531.
Повний текст джерелаАнотація:
Abstract In Memoriam—In memory of Dr. Zbigniew Magonski, a talented electronic engineer and inventor, was born in Glubczyce, Poland in 1950 and passed away in Cracow, Poland in 2017. He received M.Sc. degree in Solid State Technology from the Technical University of Wrocław, Poland in 1973, and PhD degree from the AGH University of Science and Technology, Cracow, Poland in 2000. For 15 years, he was with the R&D Center for Hybrid Microelectronics, Cracow Poland. At that time, his interest was focused on hybrid A/D, D/A converters also on DC HV power converters. Later, for 28 years, he was with the Department of Electronics, AGH University of Science and Technology, Cracow, Poland. His research interests covered ceramic microfluidic systems, hydrocarbon combustors, and high-temperature solid oxide fuel cells. In 1994–1995, he was with Summit Technology, Massachusetts, involved in a project relating to HV supplying of excimer lasers. He was a member of IMAPS US Chapter, the author of 13 patents and almost 50 technical papers connected with electronic technology. He was a caring husband and father and a good friend of many of us. We will miss you, Zbyszek. This article presents a proposal of a thermal instrument intended for the evaluation of heat energy of fluid fuels. Two thermal devices the flow meter and the combustor are the basic components of the instrument. The meter maintains a constant temperature in the vicinity of the combustion zone. The amount of heat energy in the fuel is calculated as the ratio of the electric power change expressed in Watts to the change of fuel supply delivered to the combustor within a time period of 1 s. The method enables a direct evaluation of fuel energy expressed in Joules per unit of mass or volume. For some applications, the meter may be a good alternative for a bulky bomb calorimeter.
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Magonski, Zbigniew. "Meter for the measurement heat of combustion." International Symposium on Microelectronics 2011, no. 1 (January 1, 2011): 000938–46. http://dx.doi.org/10.4071/isom-2011-tha2-paper4.
Повний текст джерелаАнотація:
This paper presents a proposal of a thermal instrument intended for the evaluation of heat energy of fluid fuels. Two thermal devices the flowmeter and the combustor are the basic components of the instrument. The meter maintains a constant temperature in the vicinity of the combustion zone. The amount of heat energy in the fuel is calculated as the ratio of the electric power change expressed in Watts to the change of fuel supply delivered to the combustor within a time period of 1sek. The method enables a direct evaluation of fuel energy expressed in Jules per unit of mass or volume. For some applications, the meter may be a good alternative for a bulky bomb calorimeter.
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Feng Wei, Ji, Li Qun Sun, Kai Zhang, XiaoYang Hu, and Shan Zhou. "Heat exchange model in absorption chamber of water-direct-absorption-typed laser energy meter." Optics & Laser Technology 67 (April 2015): 65–71. http://dx.doi.org/10.1016/j.optlastec.2014.09.015.
Повний текст джерела
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Pereselkov, A., and O. Kruglyakova. "EXPERIMENTAL STUDY OF ELEMENTARY ACTS OF HYDRODYNAMICS AND HEAT TRANSFER DURING THE INTERACTION BETWEEN WATER DROPS AND FILM AND CASTING ROLLER SURFACE." Integrated Technologies and Energy Saving, no. 4 (December 12, 2022): 3–12. http://dx.doi.org/10.20998/2078-5364.2022.4.01.
Повний текст джерелаАнотація:
Experimental studies of the boundary conditions of heat transfer for the thermally stressed state of casting rollers while are spraying with flat-jet nozzles in a thermal preconditioning unit have been carried out.
It is shown that the hydrodynamic conditions on the sprinkling surface are formed as a result of both the influx of "primary" dispersed water from the flat jet nozzle, and the "secondary" liquid coming from neighboring areas in the form of reflected drops and films.
The heat transfer effecting individual factors that form the hydrodynamic conditions on the sprinkling surface was studied separately.
The heat transfer intensity was studied depending on the spraying density, the injection-pressure drop and the temperature of the cooled surface when the "primary" drop flow runs in the heat exchange surface. The local sprinkling density of droplets on the surface under the flat-jet nozzle spray were measured using a sampling tube moved by a coordinator. At the same time, the ingress of “secondary” liquid into it was excluded.
The specific heat flux and heat transfer coefficient were determined using a heat meter made of a nichrome tape heated by direct current. In this case, the isothermality of the surface of the measuring section was ensured. Thermocouples measured the temperature of the lower surface of the tape, and then the stationary temperature of the upper surface of the heat meter sprinkled with drops is calculated.
As a result of the multivariate analysis of the experimental data, the correlation dependence of the heat transfer coefficient in dependance on the local spraying conditions of the heat meter surface was obtained.
Also, studies of the heat transfer during water film flow over the heat meter surface were carried out. A similar situation takes place when water spreads between the adjacent nozzles sprinkling zones of the roller surface.
The correlation dependence between the heat transfer coefficient, the water film speed and the cooled surface temperature was obtained.
Studies of heat transfer during combined influence of moving water film and a flat-jet nozzle drop flow on the heat exchange surface showed that the heat transfer rate is approximately 80–90 % of the arithmetic sum of the coefficients obtained by separate cooling the heat meter with drops and a water film.
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Tirado-Conde, Joel, Peter Engesgaard, Sachin Karan, Sascha Müller, and Carlos Duque. "Evaluation of Temperature Profiling and Seepage Meter Methods for Quantifying Submarine Groundwater Discharge to Coastal Lagoons: Impacts of Saltwater Intrusion and the Associated Thermal Regime." Water 11, no. 8 (August 9, 2019): 1648. http://dx.doi.org/10.3390/w11081648.
Повний текст джерелаАнотація:
Surface water-groundwater interactions were studied in a coastal lagoon performing 180 seepage meter measurements and using heat as a tracer in 30 locations along a lagoon inlet. The direct seepage meter measurements were compared with the results from analytical solutions for the 1D heat transport equation in three different scenarios: (1) Homogeneous bulk thermal conductivity (Ke); (2) horizontal heterogeneity in Ke; and (3) horizontal and vertical heterogeneity in Ke. The proportion of fresh groundwater and saline recirculated lagoon water collected from the seepage experiment was used to infer the location of the saline wedge and its effect on both the seepage meter results and the thermal regime in the lagoon bed, conditioning the use of the thermal methods. The different scenarios provided the basis for a better understanding of the underlying processes in a coastal groundwater-discharging area, a key factor to apply the best-suited method to characterize such processes. The thermal methods were more reliable in areas with high fresh groundwater discharge than in areas with high recirculation of saline lagoon water. The seepage meter experiments highlighted the importance of geochemical water sampling to estimate the origin of the exchanged water through the lagoon bed.
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Uusikivi, Jari, Jens Ehn, and Mats A. Granskog. "Direct measurements of turbulent momentum, heat and salt fluxes under landfast ice in the Baltic Sea." Annals of Glaciology 44 (2006): 42–46. http://dx.doi.org/10.3189/172756406781811150.
Повний текст джерелаАнотація:
AbstractMeasurements of under-ice turbulence were performed using an acoustic three-dimensional current meter with an attached fast-repetition temperature–conductivity sensor at two coastal areas in the Baltic Sea during two winters. Observations covered both the ice-growth and spring-melt periods. The objective of these measurements was to obtain knowledge of under-ice turbulence and oceanic heat and salt fluxes to and from the ice in the coastal fast-ice region using eddy correlation techniques. The maximum observed daily average heat flux was 1 Wm–2, and the maximum for 10 min periods was an order of magnitude larger. Under-ice turbulence was much smaller than that recorded in the oceans and in coastal regions with tide. These results provide better knowledge of under-ice turbulence and heat-flux variations and are useful for the future development of a Baltic Sea ice salinity model.
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Usoltseva, Liliya O., Dmitry S. Volkov, Evgeny A. Karpushkin, Mikhail V. Korobov, and Mikhail A. Proskurnin. "Thermal Conductivity of Detonation Nanodiamond Hydrogels and Hydrosols by Direct Heat Flux Measurements." Gels 7, no. 4 (December 3, 2021): 248. http://dx.doi.org/10.3390/gels7040248.
Повний текст джерелаАнотація:
The methodology and results of thermal conductivity measurements by the heat-flow technique for the detonation nanodiamond suspension gels, sols, and powders of several brands in the range of nanoparticle concentrations of 2–100% w/w are discussed. The conditions of assessing the thermal conductivity of the fluids and gels (a FOX 50 heat-flow meter) with the reproducibility (relative standard deviation) of 1% are proposed. The maximum increase of 13% was recorded for the nanodiamond gels (140 mg mL−1 or 4% v/v) of the RDDM brand, at 0.687 ± 0.005 W m−1 K−1. The thermal conductivity of the nanodiamond powders is estimated as 0.26 ± 0.03 and 0.35 ± 0.04 W m−1 K−1 for the RUDDM and RDDM brands, respectively. The thermal conductivity for the aqueous pastes containing 26% v/v RUDDM is 0.85 ± 0.04 W m−1 K−1. The dignities, shortcomings, and limitations of this approach are discussed and compared with the determining of the thermal conductivity with photothermal-lens spectrometry.
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Mintorogo, Danny Santoso. "THE AQUATIC-POLYCARBONATE SKYLIGHT FOR SURABAYA INDONESIA." DIMENSI (Journal of Architecture and Built Environment) 35, no. 1 (July 9, 2007): 100–106. http://dx.doi.org/10.9744/dimensi.35.1.100-106.
Повний текст джерелаАнотація:
This paper will indicate of how appropriate use of aquatic skylight module installed on buildings in the tropical zone compared to the ones in the subtropical climate. In order for energy saving strategies, the aquatic-polycarbonate skylight system is used in the tropical climate. In the tropical hot humid climate, Indonesia has received huge amount of global direct and diffuse radiations on horizontal roofs throughout the year, approximately 525 watts per square meter of solar radiation will impact on flat roofs or skylights on a clear sunny day in Surabaya city. Ironically, most of the commercial and institution buildings are equipped with Western skylight styles in Surabaya without any modifications. The aquatic-polycarbonate skylight is the system that will control daylight, scatter direct solar heat radiation, cool the indoor polycarbonate surface temperature, and collect solar hot water at the same time. The concept of using the water as shading device has three goals: first of all, the flushing water in the polycarbonate holes tries to scatter horizontal or tiled skylight direct sun-ray radiation, and minimize the direct sun heat temperature on the polycarbonate with flushing water continuously. Secondly, the sparkle flushing water in series of square holes of polycarbonate will bounce and disperse the direct sunlight into the space below enhancing daylight patterns. Finally, while bouncing, sparkling and scattering direct sunlight, those series of flushing water holes would also collect the solar heat radiation as solar hot water. Each system could works nicely to absorb, to scatter, to minimize, and to obtain the solar heat radiation for solar hot water in buildings. This strategy aims to provide a clean environment living zones with applying passive heating and cooling systems.
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Kassai, Miklos. "Energy Performance Investigation of a Direct Expansion Ventilation Cooling System with a Heat Wheel." Energies 12, no. 22 (November 8, 2019): 4267. http://dx.doi.org/10.3390/en12224267.
Повний текст джерелаАнотація:
Climate change is continuously bringing hotter summers and because of this fact, the use of air-conditioning systems is also extending in European countries. To reduce the energy demand and consumption of these systems, it is particularly significant to identify further technical solutions for direct cooling. In this research work, a field study is carried out on the cooling energy performance of an existing, operating ventilation system placed on the flat roof of a shopping center, located in the city of Eger in Hungary. The running system supplies cooled air to the back office and storage area of a shop and includes an air-to-air rotary heat wheel, a mixing box element, and a direct expansion cooling coil connected to a variable refrigerant volume outdoor unit. The objective of the study was to investigate the thermal behavior of each component separately, in order to make clear scientific conclusions from the point of view of energy consumption. Moreover, the carbon dioxide cross-contamination in the heat wheel was also analyzed, which is the major drawback of this type heat recovery unit. To achieve this, an electricity energy meter was installed in the outdoor unit and temperature, humidity, air velocity, and carbon dioxide sensors were placed in the inlet and outlet section of each element that has an effect on the cooling process. To provide continuous data recording and remote monitoring of air handling parameters and energy consumption of the system, a network monitor interface was developed by building management system-based software. The energy impact of the heat wheel resulted in a 624 kWh energy saving and 25.1% energy saving rate for the electric energy consumption of the outdoor unit during the whole cooling period, compared to the system without heat wheel operation. The scale of CO2 cross-contamination in the heat wheel was evaluated as an average value of 16.4%, considering the whole cooling season.
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Kong, Zhenyi, Yonghui Li, Shuichi Hokoi, and Shi Hu. "The rising damp in two traditional clay-brick masonry walls and influence on heat transfer performance." MATEC Web of Conferences 282 (2019): 02097. http://dx.doi.org/10.1051/matecconf/201928202097.
Повний текст джерелаАнотація:
This paper studies the law of capillary water rise in the brick solid wall and the brick cavity wall under the influence of high-humidity wall foundation. It is found that the rising height of the capillary water sharp front is proportional to the time to the 0.5 power, but the coefficient is related to the wall structure, and the speed in cavity wall is higher than that in the solid wall. The heat flow meter method was used to compare the influence of the capillary water to the heat transfer when it rises to different heights. It is found that the presence of capillary water has a direct impact on the heat transfer coefficient of the wall. The presence of capillary water may increase the heating load by 11.1% and the cooling load by 15% of a common historical building in hot summer and cold winter area of China.
Частини книг з теми "Direct heat meter"
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Rohling, Eelco J. "ENERGY BALANCE OF CLIMATE." In The Climate Question. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190910877.003.0006.
Повний текст джерелаАнотація:
The Sun is the ultimate energy source for climate. The Sun radiates toward Earth at an almost constant intensity of about 1360 watts per square meter (W/ m2), as measured above the Earth ’s atmosphere. Most of this radiation takes place in the short ultra- violet and visible light wavelengths. We refer to it as incoming short- wave radiation (ISWR; the wavelengths are short because the Sun radiates at very high temperatures of about 5500°C). Earth is not a two- dimensional disk, but a 3- dimensional sphere. Its day- side faces the Sun and receives radiation, while its night- side is directed away from the Sun and does not receive solar radiation. As a result, the global average energy received from the Sun per square meter of Earth surface is the energy received by the day- side of Earth averaged over the surface area of the entire sphere. When we do the mathematics, this gives an average input of solar radiation into every square meter of Earth, at the top of the atmosphere, of 340 W/ m2 (Box 3.1). That is the value that things work out to when considering the ISWR from the Sun in a continuous and globally equally “smeared out” sense, and that is what matters when we are working out the balance between energy gained and lost by Earth (Box 3.2). Many people are puzzled by the fact that we talk only about energy from the Sun. They then especially wonder why we ignore heat input from the deep Earth, and in particular from volcanoes, which after all are very hot. But in spite of the spectacular shows of heat, steam, gases, and primordial mayhem that volcanoes put on display, they turn out to be almost negligible in terms of heat flow into the climate system. Compared with the global average solar energy gain of 340 W/ m2, recent assessments show that total heat outflow from the Earth’s interior is not even 0.09 W/ m2.
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Spiel, Christiane, Petra Gradinger, and Dagmar Strohmeier. "Cyberpesten: definitie, metingen en bevindingen." In Boos! Over agressie, opvoeding en ontwikkeling, 101–14. 2nd ed. Uitgeverij SWP, 2016. http://dx.doi.org/10.36254/978-90-8850-292-7.08.
Повний текст джерелаАнотація:
Cyberpesten wordt omschreven als een agressieve, doelbewuste gedraging door een of meer personen die gedurende een langere periode herhaald wordt en waartegen het slachtoffer zich niet goed kan verdedigen, en waarbij gebruik wordt gemaakt van digitale contactvormen (Smith et al., 2008; zie ook Menesini & Nocentini, 2009). Door de toename in en verspreiding van moderne technologieën is een nieuwe vorm van agressie en pesterijen ontstaan. Deze nieuwe vorm wordt door onderzoekers aangeduid met de termen ‘cyberpesten’, ‘digitaal pesten’ of ‘internetpesten’. Deze termen verwijzen naar doelbewuste en herhaalde aanvallen tegen een andere persoon door middel van digitale media. Hieronder vallen bijvoorbeeld: beledigende e-mails en sms’jes, beledigingen via chatrooms, direct chatcontact, foto’s of filmpjes op mobiele telefoons of het internet, uitsluiting van sociale netwerken, en het zich toe-eigenen van de persoonsgegevens van een andere persoon. Cyberpesten is voor jongeren in verschillende westerse landen een bedreigende ervaring, hoewel het in verschillende culturen, contexten en wat betreft persoonlijke kenmerken in verschillende mate voorkomt. Volgens een recente schatting loopt in Europa (vergelijk Livingstone, Haddon, Görzig, & Ólafsson, 2011) en in Noord-Amerika (vergelijk Ybarra, Diener-West, & Leaf, 2007) cyberpesten op tot bijna 10%. Cyberpesten is een onderwerp dat niet alleen sinds het begin van deze eeuw door onderzoekers volop wordt belicht, ook de media hebben hier naar aanleiding van spectaculaire voorvallen in enkele scholen veel aandacht voor. Ondanks deze aandacht zijn er nog veel onbeantwoorde vragen over cyberpesten. Onderwerp van discussie is met name de relatie met ‘face-to-face’ pesten ofwel traditioneel pesten. Het eerste deel van dit hoofdstuk richt zich op conceptuele en theoretische overeenkomsten en verschillen tussen cyberpesten en ‘face-to-face’ pesten en op de complexiteit van het meten hiervan. Het tweede deel bestaat uit empirisch onderzoek naar het naast elkaar voorkomen van cyberpesten en traditioneel pesten, naar risicogroepen qua aanpassingsproblemen en naar motieven voor cyberpesten.
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Verschuur, Gerrit L. "Solar System Debris." In Impact! Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195101058.003.0006.
Повний текст джерелаАнотація:
The object that slammed into the earth to precipitate the dinosaur demise was no stranger to the solar system; it had been lurking about its outer regions ever since the sun and planets formed 4.5 billion years ago. Like a construction site littered with builder’s materials after the work is done, debris left over from the formation of the sun and planets is scattered throughout the solar system in the form of comets and asteroids. From among this population the great impactor that triggered the K/T extinction event originated. Unfortunately there is no way to cart the debris away so that earth won’t smash headlong into another comet or asteroid. Whether we like it or not, we live with the hazard of occasionally finding some of this stuff directly in the path of the earth’s orbit around the sun. In fact, every day something from space slams into our planet. The generic name for icy, dusty, rocky, or metallic objects that wander about in interplanetary space is “meteoroid.” After the process of planetary formation was essentially complete, a great deal of meteoroidal material was left over. Depending on its fate, a meteoroid hurtling into the earth’s atmosphere today earns a new name. It is called a meteor in the case of a tiny pea-sized particle that burns up in the atmosphere to produce a momentary fiery trail known as a shooting star. These have long been the focus of superstitions because of their obvious associations with the heavens and, therefore, with gods that might reside there. Even in our time, it is common to “make a wish upon a star” when a meteor is seen. Every night you can see dozens if not hundreds of meteor trails. On a good night in a clear location half a dozen an hour is about as good as you can expect. In addition to the meteors that burn up to leave a visible trail, there are countless that are too small to be seen, enough to allow tens of millions of wishes a day. These heat the atmosphere enough to produce trails of hot gas that reflect radar signals.
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"than its original energy. The ejected electron (Compton electron) has enough kinetic energy to cause excitations and ionizations in the absorber atoms. It thus interacts with the absorber in the same way as the ejected secondary electrons produced by an electron accelerator beam (Fig. 12b). Because Compton electrons are produced when gamma or x-ray photons interact with a medium, and because the Compton electrons cause ionizations and excitations in the same way as secondary electrons produced by accelerator beam electrons, the radiation-induced chemical changes in the irradiated medium are largely the same, regardless of the type of radiation used. The purpose of dose meters is to measure the amount of radiation energy absorbed by the irradiated product. The instrument that gives a reading of absorbed dose directly is the calorimeter. It measures the total energy dissipated or the rate of energy dissipation in a material in terms of the thermal properties of the absorbing body. This instrument, therefore, is considered to be an absolute dose meter that can be used for calibrating other dose meters. The principle of radiation calorime try is implicit in the definition of the radiation dose unit 1 Gy (gray) = 1 J (joule)/ kg. Ideally the temperature elevation should be measured in the irradiated food product itself— but in practice this is usually not done because the thermal properties of foodstuffs vary widely. A substance with known, reproducible thermal properties is taken instead, which serves as a heat-sensing calorimetric body, included in an adiabatic system (adiabatic = without transmission of heat). Water, graphite, aluminum, or a water-equivalent plastic is usually chosen, and the thermal change is determined by small calibrated thermocouples or thermis tors embedded in the calorimetric body. The practice of using radiation calorimetry is not simple, and ways to use it in a routine fashion have been developed only recently (24,25). Because the process of temperature elevation should run under adiabatic or quasi-adiabatic conditions, the dose has to be applied in a very short time. Calorimetry is therefore mostly used for measuring electron accelerator beam doses. The absorbed dose in the calorimetric body can be converted to that of the material of interest (foodstuff) by taking into consideration the different density and the different energy absorp tion coefficients of the two materials. The temperature elevation depends on radiation dose and on the specific heat of the material irradiated. A dose of 10 kGy causes a temperature elevation as follows: 2.3K in water (specific heat 4.2 kJ/kg • K) 6.2K in dry protein (specific heat 1.6 kJ/kg • K) 7.1K in dry carbohydrate (specific heat 1.4 kJ/kg • K) 12.5 K in glass (specific heat 0.8 kJ/kg • K)." In Safety of Irradiated Foods, 49. CRC Press, 1995. http://dx.doi.org/10.1201/9781482273168-38.
Повний текст джерелаТези доповідей конференцій з теми "Direct heat meter"
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Bergin, Mike, Ettore Musu, Sage Kokjohn, and Rolf D. Reitz. "Examination of Initialization and Geometric Details on the Results of CFD Simulations of Diesel Engines." In ASME 2009 Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/ices2009-76053.
Повний текст джерелаАнотація:
Computational Fluid Dynamic (CFD) simulations using the AVL Fire and Kiva 3v codes were performed to examine commonly accepted techniques and assumptions used when simulating direct injection diesel engines. Simulations of a steady state impulse swirl meter validated the commonly used practice of evaluating the swirl ratio of diesel engines by integrating the valve flow and torque history over discrete valve lift values [1]. The results indicate the simulations capture the complex interactions occurring in the ports, cylinder and honeycomb cell impulse swirl meter. The commonly adopted axisymmetric assumption for an engine with a centrally located injector was tested by comparing the swirl and emissions history for a motored case and a double injection low temperature combustion case. Consideration of the detailed engine geometry including valve recesses in the piston and the head lowered the peak swirl ratio at TDC by approximately 10% compared to the simplified no-recess case. The corresponding combusting cases also had different heat release and emissions predictions but could be partially compensated for by lowering the initial swirl ratio for the axisymmetric case.
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Xu, Feng, Qiusheng Liu, Satoshi Kawaguchi, and Makoto Shibahara. "Experimental Study on Transient Heat Transfer for Helium Gas Flowing in a Minichannel." In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16697.
Повний текст джерелаАнотація:
Abstract The blanket modules of first wall need bear tremendous heat flux due to the very high temperature of plasma in the nuclear fusion reactor. Therefore, it is significant to clarify the knowledge of transient heat transfer process for helium gas flowing in the tubes installed in the blanket modules. In this research, the transient heat transfer process of turbulent forced convection for helium gas flowing in a horizontal minichannel was experimentally investigated. The test tube made of platinum with the inner diameter of 1.8 mm, the wall thickness of 0.1 mm and the effective length of 90 mm was heated by a direct current from power source. The heat generation rate of the test tube, Q̇, was raised with an exponential function, Q̇ = Q0 exp(t/τ), where Q0 is the initial heat generation rate, t is time, and τ is e-folding time of heat generation rate. The heat generation rates of the test tube were controlled and measured by a heat input control system. The flow rates were adjusted by the bypass of gas loop and measured by the turbine flow meter. The experiment was conducted under the e-folding time of heat generation rate ranged from 40 ms to 15 s. Based on experimental data, it is obvious that the heat flux and temperature difference between surface temperature of test tube and bulk temperature of helium gas increased with the exponentially increasing of heat generation rate. At the same flow velocity, the heat transfer coefficients approached constant values when the e-folding time is longer than about 1 s (quasi-steady state), but increased with a decrease of e-folding time when the e-folding time is smaller than about 1 s (transient state). The heat transfer coefficients increased with the increase in flow velocities but showed less dependent on flow velocities at shorter e-folding time. Furthermore, the Nusselt number under quasi-steady and transient condition was affected by the Reynolds number and the Fourier number.
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Gallman, Benjamin, B. Terry Beck, and Mohammad H. Hosni. "Direct Pressure Measurement and Flow Visualization of Cavitation in a Converging-Diverging Nozzle." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-12236.
Повний текст джерелаАнотація:
Abstract While normally certain unwanted phenomena are to be avoided, cavitation has useful engineering applications. Specifically, it can be used as to create cooling potential in a novel non-vapor compression refrigeration process. Cavitation occurs when the pressure of the working fluid (compressed liquid) drops below the saturation pressure. Since the cavitation (flash) results in an abrupt reduction in temperature, the working fluid can take in energy as heat from the surroundings during cavitation, which results in a cooling potential (refrigeration). In a converging-diverging nozzle, as the fluid passes through the throat the pressure decreases. If the pressure drops below the saturation pressure, cavitation can occur. The current research focuses on measuring the pressure nearby the cavitation front, and the associated pressure distribution within the two-phase region, in a converging diverging nozzle. A blow-down flow system was used to conduct measurements with water as the working fluid. The flow rate was measured with a rotameter and a Coriolis flow meter. The nozzle is a transparent 3D printed nozzle with an inlet diameter of 9.3 mm, throat diameter of 1.71 mm, and an outlet diameter of 9.3 mm. The upstream reservoir was kept at atmospheric pressure and was elevated above the level of the nozzle inlet. The downstream reservoir was evacuated to create a pressure difference that would drive fluid through the nozzle. The pressure distribution within the nozzle was measured using eight pressure transducers connected to the nozzle with 0.006” diameter taps, and a high-speed camera was used to capture flow visualization. The pressure distribution was measured for steady cavitating flow at several back pressures, and during an increasing flow rate to capture pressure changes during cavitation initiation. These results give direct pressure measurements during cavitating flow, along with the accompanying flow visualization. They should prove useful for furthering the understanding of the metastable fluid mechanics behavior of cavitating flows, and thereby contribute to the ability to ultimately maximize the cooling potential of the cavitation phenomena.
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Kumar Juvva, Srihari Dinesh, Sathesh Mariappan, and Abhijit Kushari. "Open Loop Active Control of Combustion Noise in Gas Turbine Combustor." In ASME 2015 Gas Turbine India Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gtindia2015-1340.
Повний текст джерелаАнотація:
The presented study is on a laboratory scaled industrial gas turbine combustor of intensity 25MW/m3 atm, where an open loop active control technique is investigated. Combustion noise is classified as direct and in-direct combustion noise. The present study is focused on the investigation of direct combustion noise. It occurs when the volume of the gas fluctuates due to the fluctuations in heat release rate, caused perhaps due to flow turbulence. This results in sound waves, which propagate outside the boundary of the flame. The radiated acoustic waves are reflected from the boundaries of the combustion chamber, perturbing the fuel flow rate and hence the spray characteristics. This eventually leads to perturbation in the heat release rate and thus a feedback loop is established. At certain conditions, if the unsteady heat release rate drives the acoustic oscillations, satisfying Rayleigh criterion, pressure oscillations grow leading to discrete tonal sound and this phenomena is termed as combustion instability. Experiments are performed in a scaled down swirl stabilized liquid fueled gas turbine combustor, where a new scheme for open-loop control of combustion noise using periodic fuel injection is employed without drastically altering the combustor design or forfeiting its performance. Fuel is modulated in the frequency range of 0.6 to 5 Hz with various duty cycles [25–75%] using square wave. Fuel modulation is achieved by passing fuel through a direct current (DC) powered solenoid valve, which is being controlled using a custom-made circuit. The modulated fuel enters the combustor through an air-blast atomizer and is metered through a turbine flow meter. The main objective of this paper is to investigate the potential of active control to reduce combustion noise in laboratory scaled gas turbine combustor. Pressure transducer is used to capture the sound pressure level inside the combustor. A reduction in overall sound pressure level of 14dB is achieved by modulating fuel with 50% duty cycle at 1.5Hz.
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Anandram, V., S. Ramakrishnan, J. Karthick, S. Saravanan, and G. LakshmiNarayanaRao. "Engine Analysis of Single Cylinder DI Diesel Engine Fuelled With Sunflower Oil, Sunflower Oil Methyl Ester and Its Blends." In ASME 2006 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/icef2006-1573.
Повний текст джерелаАнотація:
In the present work, the combustion, performance and emission characteristics of sunflower oil, sunflower methyl ester and its blends were studied and compared with diesel by employing them as fuel in a single cylinder, direct injection, 4.4 KW, air cooled diesel engine. Emission measurements were carried out using five-gas exhaust gas analyzer and smoke meter. The performance characteristics of Sunflower oil, Sunflower methyl ester and its blends were comparable with those of diesel. The components of exhaust such as HC, CO, NOx and soot concentration of the fuels were measured and presented as a function of load and it was observed that the blends had similar performance and emission characteristics as those of diesel. NOx emissions of sunflower oil methyl ester were slightly higher than that of diesel but that of sunflower oil was slightly lower than that of diesel. With respect to the combustion characteristics it was found that the biofuels have lower ignition delay than diesel. The heat release rate was very high for diesel than for the biofuel.
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Hermansson, Robert, Ville Närvänen, Jyrki Kajaste, Olof Calonius, Matti Pietola, and Petri Kuosmanen. "Experimental Study on Energy Efficiency of Two-Cylinder Direct Driven Hydraulic System in a Large-Scale Test Bench." In ASME/BATH 2021 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fpmc2021-68797.
Повний текст джерелаАнотація:
Abstract In this research the energy efficiency of a pump controlled direct driven hydraulic (DDH) system is experimentally tested and analyzed. The test bench uses two cylinders’ cross-connection to rotate the middle joint of the 5-meter-long pivot arm which is loaded with unequal load of maximum 1685 kg. Originally the test bench is designed to study the application of DDH in the case of an articulated steering system, but in this research the system is treated as load lifting and load lowering application. The power pack of the test bench features a permanent magnet servo motor and a bent-axis, fixed-displacement hydraulic motor-pump unit. A separate charge pump circuit is attached, which also controls the servo motor and pump case temperature and takes care of fluid heat management as well as filtering. An extensive CAN-network is utilized for measurement and control. The motion of the test bench is driven with position control to give reproducible lifting and lowering cycles with different loads and velocities. Three motion cycles are executed involving three different loads, nine combinations in total, to study their effect on energy efficiency in load lifting and load lowering situations. Mechanical input power is measured between the electric motor and pump, hydraulic power is measured at the pump outlet and at the cylinder ports, and finally the mechanical output power is calculated for the cylinder-to-mechanical interface. Energy losses are determined as well as the overall energy efficiency of the hydraulic system. The research focuses on the hydraulic system and therefore the electric input power to the system and the regenerated electric power in load lowering is left out of the study. However, the regeneration potential in load lowering part of the cycles is measured as the available electric motor shaft power. In load lifting, the total energy efficiency of the hydraulic system was at its best at 82% when using the maximum additional load of 1685 kg and the lowest lifting velocity of 0.1 rad/s. Energy efficiency of load lowering was at its best in the same cycle with 77% of the energy recovered from the pump-motor’s shaft. High dependency on load and velocity was detected, because the total efficiency in lifting decreased to 44% with highest velocity (0.3 rad/s) and lowest load (445 kg). In lowering, during the same cycle, the total efficiency was −17%, meaning that gravity loading alone could not produce fast enough motion and that active input power was needed. In conclusion, very good energy efficiency could be achieved when operating against high enough loading. Operating at partial loads and with higher velocities will clearly reduce energy efficiency, emphasizing the need for careful dimensioning of all the power train components.
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McKee, Robert J. "Mapping and Predicting Air Flows in Gas Turbine Axial Compressors." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38745.
Повний текст джерелаАнотація:
Determining the airflow through a gas turbine’s axial compressor is not a simple or one step process as many factors affect flow and there is seldom a flow meter or a means to directly measure airflow rate. Speed of the compressor, inlet pressure and temperature, and resistance or backpressure at the compressor’s outlet all affect the amount of airflow. The type of gas turbine, single or twin spool, the magnitude of power produced, the use of bleed or bypass valves, the power turbine speed, and operating conditions all have influences on the amount of airflow. Despite this, there are several reasons why an estimate of airflow is useful for understanding and describing the behavior and performance of gas turbines. The amount of airflow compared to fuel flow determines the composition and condition of the exhaust gases and is directly related to the turbine’s power output, heat rate, and waste heat recovery potential. A predicted airflow rate and the corresponding axial compressor discharge pressure can be used to identify deterioration in performance and to estimate emission characteristics of a unit. This paper presents an approach based on easily obtained gas turbine data, such as the design point data, test stand data, or manufacturer’s curves for the compressor. Compressor performance curves may be obtained from the manufacturer or by mapping compressor output during normal operations. A great deal of information has been presented in the literature about the performance of gas turbines and axial compressors but this paper focuses on methods that are sufficiently simple and direct that users can obtain an estimate of their unit’s airflow, References 1, 2, and 3. Some manufacturers provide computer data bases or on-line control panel estimates of gas turbine airflow but in these cases, the user has no idea what causes a change. Detailed performance curves for axial compressors are usually not available, however, through the methods presented in this paper, a reasonable approximation of the operating curves can be developed and used to estimate axial compressor airflow over the full range of normal operations. The methods described are based on tracking and mapping a compressor’s operations over a period of time and relating compressor output to other performance parameters and known conditions (design point) in order to establish a normally expected airflow rate.
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Massini, D., T. Fondelli, B. Facchini, L. Tarchi, and F. Leonardi. "Windage Losses of a Meshing Gear Pair Measured at Different Working Conditions." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76823.
Повний текст джерелаАнотація:
In recent years the aero-engine community is looking towards the reduction of specific fuel consumption by increasing the efficiency of gearing systems. Considering their weight contribution, internal power losses and lubrication requirements, they have indeed a direct impact on the engine overall efficiency. Even though nowadays gears have reached very high efficiencies, over 99%, all the power dissipated through losses is converted into heat that must be removed by the lubrication system. Heat reduction is hence beneficial for minimizing lubrication system dimensions that is crucial in aero engine applications where it is mandatory to limit the weight of every component. Among the sources of loss, two main categories may be distinguished: load dependent and load independent losses. The first ones are due to the transmission of torque and have been deeply studied in the last years, the latter are related to fluid-dynamic interaction between gears and the surrounding environment, they are negligible at low pitch line velocities, but become very important in high speed applications, typical of turbomachinery. This work deals with an experimental investigation of the load independent losses due to a couple of spur meshing gears working at different conditions in presence of an oil-jet lubrication system. The test rig allows the gears to rotate, at different velocities up to 15000 rpm, in a controlled environment contained in a sealed box. Test rig pressure can be imposed (0.3–1.0 bar) and monitored as well as the oil jet conditions, in terms of mass flow rate (jet volume flow rate up to 1.65 litres per minute), temperature (80–140 °C) and inclination angle. A high precision bearing-less torque meter, equipped with a speedometer, was exploited to measure at the same time the torque losses and rotating speed. Results of the experimental survey allowed a better understanding of load independent losses at pitch line speed up to 100 m/s and in different environmental conditions.
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Massini, D., T. Fondelli, A. Andreini, B. Facchini, L. Tarchi, and F. Leonardi. "Experimental and Numerical Investigation on Windage Power Losses in High Speed Gears." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64948.
Повний текст джерелаАнотація:
Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. The transmission system in fact has a direct impact on the engine overall efficiency by means of its weight contribution, internal power losses and lubrication requirements. Thus, an evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Gears are among the most efficient power transmission systems, whose efficiencies can exceed 99 %, nevertheless in high speed applications power losses are anything but negligible. All power dissipated through losses is converted into heat that must be dissipated by the lubrication system. More heat leads to a larger cooling capacity, which results in more oil, larger heat exchangers which finally means more weight. Mechanical power losses are usually distinguished in two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid-dynamics of the environment which surrounds the gears, namely windage, fluid trapping and squeezing between meshing gear teeth and inertial losses resulting by the impinging oil jets, usually adopted in high speed transmission for cooling and lubrication purposes. The relative magnitude of these phenomena is strongly dependent on the operative conditions of the transmission. While load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. Among fluid-dynamic losses, windage is extremely important and can dominate the other mechanisms. In this context, a new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry measurements for investigating the flow-field surrounding the rotating gear. The experiment has been computationally replicated, performing RANS simulations in the context of conventional eddy viscosity models. The numerical results were compared with experimental data in terms of resistant torque as well as PIV measurements, achieving a good agreement for all of the speed of rotations.
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Alexandrescu, Aurora C., Simona Adina O. Alexandrescu, and Constantin Adrian O. Alexandrescu. "Contributions Concerning the Power Optimization of the Pumping Stations." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55007.
Повний текст джерелаАнотація:
Profitability of water distribution activity depends largely on the relationships between operational capability and service costs, related to supplier’s performance, volume of distributed water and effective operating costs. The main variables that influence the total selling price are required investment value, specific consumption of electrical energy for pumping power, unit price of the electrical energy and total volume of monthly consumed water billed. The selection of rehabilitation and modernization measures must rely on market studies results that appropriately establish the quantities of water that may be distributed and billed. Present and future water requirements will be determined based on the analysis of actual operation data and on estimation of future trends in water consumption on national and international levels. The optimization calculation will use two target functions: total maximum efficiency and total electric power consumption required for transport of each cubic meter of supplied water, and cubic meter of sewage water, respectively. The mathematical methods may be improved by taking into account all active consumers in the network with simultaneous water requirements, at each moment of the day. Using several original mathematical algorithms, authors developed a computer program that calculates the functional parameters of the ensemble pumping station – hydrophore – pipe distribution network, as well as the available consumer parameters. This may be accomplished at each moment in time, depending on the number of active consumers simultaneously connected to the supply network, in the hypothesis of a minimum price of cubic meter of pumped water. This paper proposes a solution of the problem of reducing production costs for supplied domestic water, which directly affects the reduction of the electric power consumption.