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ELECTROENERGETICS
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REACTIVE POWER IN THE LONG ELECTRICAL LINES
Authors: Berzan V., Rimschi V., Patsiuk V., Tîrsu M. Institute of Power Engineering of the Academy of Scienсes of Moldova
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Abstract: This paper presents a numerical method for the calculation of electric circuits with distributed parameters with losses that may vary over time. It is proposed to use the energy integral in order to estimate the accuracy of numerical solutions. The elaborated numerical scheme, named Albatross, is conservative with minimal dissipation and dispersion. These properties lead to the fact that the computational error does not accumulate, that gives the possibility to realize the transparent calculations of non stationary solutions without loss of accuracy at large time intervals corresponding to 300…500 electromagnetic wave runs along the line length right up to steady-state regime. The results of calculations for non-homogeneous circuits with distributed parameters are presented graphically. These results can be used as a model to develop new approximate methods for numerical solution of electrotechnical problems. The solutions of these problems have been obtained by means of operator method, complex amplitude method, Fourier method as well as by numerical method Albatross. The results of calculations for various modes in the half-wave transmission line are represented. The comparison between the physical and mathematical experiments in analyzing of different regimes in half-wave electrical transmission line is represented. The comparison of accuracy of the solutions obtained by proposed method, by Finite Difference Time Domain (FDTD) method and by Godunov’s scheme for telegraph equations is carried out. It is illustrated, that FDTD method has some limited application for solving the telegraph equations in spite of the fact that it is of second order of accuracy. |
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Keywords: long transmission line, telegraph equations, non-stationary currents and voltages, distributed and lumped parameters.
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HEAT AND POWER ENGINEERING
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POWER SUPPLY UNIT FOR COMMERCIAL GREENHOUSES
Authors: Sit Mikhail, Sit Boris Institute ofPower Engineering of the Academhy of Sciences of Moldova
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Abstract: The aim of the work is to develop the energy efficient schemes for energy supply of the industrial greenhouse designed for year-round production of plants that requires year-round maintenance of strongly prescribed temperature and humidity inside. We have been elaborated the complex "gas driven heat pump “water-air” – electric generator" (for use during the heating season) as well as the "gas driven heat pump “water-air” – electric generator – desiccant – evaporative chiller" (for use during the off-season). Proposed structures have a high energetic and economic efficiency as compared with conventional schemes (boiler - chiller). The proposed complex ensures year-round maximum COP of heat pump and maximum performance of gas engine. |
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Keywords: cogeneration, heat pump, gas engine.
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FLUOROETHERS AS A WORKING FLUIDS FOR LOW TEMPERATURE ORGANIC RANKINE CYCLE
Authors: Artemenko S.V. Educational and Research Institute of Refrigeration, Сriotehnology and Eco-Energetics Odessa National Academy of Food Technologies, Ukraine
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Abstract: Hydrofluoroethers as a new class of working fluids for the organic Rankine cycle have been considered to utilize the low-potential waste heat. Temperature range 300…400 K was chosen to provide energy conversion of waste heat from fuel cells. The direct assessment of the efficiency criteria for the Rankine cycle via artificial neural networks (ANN) was used. To create ANN the critical parameters of substance and normal boiling temperature as input were chosen. The forecast of efficiency criteria for the Rankine cycle as output parameter which reproduces the coefficient of performance with high accuracy and without thermodynamic property calculations was presented. |
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Keywords: working fluids, Organic Rankine cycle, coefficient of performance, artificial neural networks, hydrofluoroethers.
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PROCESSES OF HEAT-MASS-TRANSFER IN APPARATUS OF SOLAR ABSORBING REFRIGERATION SYSTEMS
Authors: Doroshenko A.V., Ludnitsky K.V. Educational and Research Institute of Refrigeration, Сriotehnology and Eco-Energetics Odessa National Academy of Food Technologies, Ukraine
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Abstract: Ideology of development of the solar refrigeration systems and systems of air-conditioning, based on the use of absorbing cycle and solar energy for the regeneration of absorbent solution, is presented in the article. The processes of joint heat-mass-transfer are considered in the direct and indirect types of evaporated coolers taking into account the phenomenon of re-condensation of aquatic steams at the low temperature evaporated cooling of environments. The pre-liminary analysis of possibilities of the solar systems is executed as it applies in relation to the tasks of cooling of envi-ronments and air-conditioning systems. |
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Keywords: the Solar systems, drainage of air, cooling of environments, air-conditioning systems, heat-mass-transfer apparatus, absorption, desorption, evaporated cooling.
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RESEARCH OF SHORT DIFFUSERS IMPLEMENTATION EFFICIENCY IN COMPACT HEAT EXCHANGERS
Authors: Yusha V.L., Vasilyev V.K., Filkin N.YU., Shipunova A.A. Omsk State Polytechnic University
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Abstract: Increasing of efficiency of air condenser with the help of cooling air distribution is considered. The relevance of research connected with preservation of the compact sizes of the heat exchange device is presented. The analysis of shortcomings of the existing designs on the basis of the tubular heat exchanger with the short diffuser is carried out. Various devices and recommendations about improvement of operation of the short diffuser are considered. The research objective consisting in an assessment of influence of a configuration of flowing part of the short diffuser on overall performance of the heat exchange device is formulated. The methodology of carrying out the engineering analysis of cooling equipment on the base of ANSYS CFX is developed. The calculation of tubular cooler characteristics with several alternatives of the inlet section is made, the analysis of results from the point of view of losses of pressure in the diffuser and amounts of the taken-away heat is carried out. The improvement in cooler work using guide rails for its inlet section is discovered. |
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Keywords: heat exchanger efficiency, short diffuser, air distribution, additional guide rails.
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EFFICIENCY OF MULTI-MODULE SOLAR COLLECTORS AS A PREFIX TO A BOILER
Authors: Denysova A.E., Mazurenko A.S, Denysova A.S. Odessa National Polytechnic University, Ukraine
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Abstract: Influencing factors on thermal and economic efficiency of the combined of heat supply installation are established. Constructive circuits of solar heat supply "prefix" interaction with boiler installation are worked out. Mathematical models of heat exchange processes in elements of combined heat supply system with the account solar engineering characteristics are developed. The techniques of analysis of efficiency of multi-modular system of solar collectors with compulsory circulation for water heating boiler allowing calculating of efficiency factor; heat removal factor and heat transfer factor with the account of construction and operation conditions of alternative heat supply system are presented. |
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Keywords: solar collector, efficiency, compulsory circulation.
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MATHEMATICAL MODEL OF THE «PISTON» DISPLACEMENT OF IMMISCIBLE LIQUIDS DURING FILTRATION IN A POROUS MEDIUM
Authors: Polozhaenko S. A., Lysenko N. A. Odessa National Polytechnic University, Ukraine
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Abstract: Mathematical model of the front displacement in porous media multicomponent systems, presents filterable immiscible (including abnormal) fluids. In real application tasks it is given a qualitative description of the process of displacement in a multicomponent system with an intermediate agent «piston». Mathematical model of a class of problems of the frontal displacement for multicomponent systems is formulated as a variation inequality and provides a simple numerical implementation. |
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Keywords: multicomponent systems, frontal expulsing, «stagnant zone», maximum gradient, mathematical model, variation inequality.
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DEVELOPMENT OF THE METHOD OF CALCULATION OF CHILLERS WITH THE COMBINED-COOLED CONDENSER
Authors: Fot A.N., Vasiliev V.K. Omsk State Polytechnic University, Russian Federation
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Abstract: Combined cooling of condenser ensures stabilization of the condensation pressure and significantly reduces the consumption of cooling water and electricity. Exisiting methods of calculus of condenseres are applicable for condensers with air or with water cooling and are not valid when designing a condenser with combined cooling. The economical and technical recommendations for calculus must be elaborated in dependence of part of the time of using water or air for condenser unit cooling throughout the year. The mathematical model describing the operation of all elements of the chiller, as well as their technical and economic performances has been elaborated. The model includes analysis of the chiller during the whole period of operation and determines what share of water and air for cooling of condenser is the best. The analysis takes into account the cost of cooling water, power, energy costs for transporting the cooling water, for compressor drive, as well as the capital and operating costs. |
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Keywords: combined cooling, condensing unit, water and air cooling, the environment, energy savings, the mathematical model, the chiller.
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THE EXPERIMENTAL RESEARCH OF THE SEASON-ACTING THERMAL STABILIZER OF SOIL
Authors: Evdokimov V.S., Maximenko V.A., Vasilyev V.K., Tretyakov A.V. Omsk State Technical University
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Abstract: The scope of the research is the solution of the problem of saving of the state of permanently frozen soil in conditions of northern construction. The soil thermal stabilizers are used for permafrost maintenance. We carried out the work which purpose is the research of dynamics of temperature regime of the soil around the thermal stabilizer in the winter and summer for a climatic zone of the South of Western Siberia. Temperature fields of the soil around the thermal stabilizer are experimentally obtained. The design results are confirmed with pilot research. For evaluation of the of the work of a vaporizing zone of the thermal stabilizer we have introduced a new parameter – the volumetric heat content, which takes into account not only the volume of frozen ground, but it’s temperature level. It was elaborated and tested the promising example of thermopile. |
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Keywords: termal stabilization of soil, temperature fields, thermopile, frozen soil.
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USE OF GAS BURNERS TYPE "DAVA" OPERATING UNDER VARIABLE LOAD TO PRODUCE HEAT AND HOT WATER
Authors: Daud V. National Agency for Energy Regulation of the Republic of Moldova
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Abstract: The article brings additional information referred to upgraded gas burners type "DAVA", which are characterized by high performance at variable load. Adaptation of burner operation is carried out automatically. There are presented design features that allow increase of the efficiency and the reliability of these burners at variable load, and reducing natural gas consumption. The range of variation of the coefficient of excess air affects the efficiency of the burner. The experimental results of the tests of gas burners of different power had confirmed the economic effect of the upgraded burners at heat production. It is proved that economic effect increases with increasing of burner output and of operation time during the season. |
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Keywords: burner, gas-air mix, variable load, efficiency.
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INFORMATION SYSTEM
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STEGANOGRAPHIC METHOD VERIFYING THE INTEGRITY AND AUTHENTICITY OF EMBEDDED INFORMATION
Authors: Kobozeva A.A., Kozina M.A. Odessa National Polytechnic University, Ukraine
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Abstract: The paper focuses on the steganographic method that carries out simultaneous effective solution for creation of covert communication channel within the channel for public use, check of the integrity and authenticity of the transmitted additional information. These tasks define the so-called three-pronged task (TT) that is of current interest, but today, according to the data available from the open press, has no satisfactory solution. This is connected with the complexity of TT and moreover a covert communication channel itself requires additional guaranteeing the reliability of perception and insensitivity of formed steganomessage against disturbing influences. The digital image stands as a container. The additional embedded information that is the result of pre-primary encoding of confidential information and the subsequent secondary coding using a secret key for authentication is represented as a binary sequence. Developed steganomethod for solving TT, ensures the reliability of perception of formed steganomessage, is resistant to attacks against embedded messages and allows to effectively decode the transmitted information even in the event of a breach of its integrity, that is evidenced by the results of a computational experiment. |
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Keywords: steganography method, integrity, authenticity, discrete Fourier transform, a digital image.
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RENEWABLE ENERGY SOURCES
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PLASMA GASIFICATION – THE WASTE-to-ENERGY SOLUTION FOR THE FUTURE
Authors: Birsan Nicolae Westinghouse Plasma Corp.
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Abstract: Plasma WtE is currently subject of extensive research and a number of companies across the globe are trying to develop a suitable, eco-friendly and efficient WtE technology for the future. While all of these companies are still working on concept designs or small-scale prototypes, there is one company already building large industrial scale plasma gasifiers around the globe to treat MSW, Industrial and Toxic waste all together. In 1999 in Japan, Hitachi Metals and Westinghouse Plasma Corp (“WPC”) built the World’s First commercial demonstration plasma WtE plant. Hitachi Metals operated the plant for one year on municipal solid waste and obtained a certification from the Japan Waste Research Foundation (JWRF). Subsequently, Hitachi Metals leveraged this success into the two commercial plants at Mihama-Mikata and Utashinai in Japan, both having at the very core the now proven Westinghouse Plasma gasification technology. For more than 20 years, Westinghouse Plasma Corp (WPC) has been leading the technology platform for converting the world’s waste into clean energy for a healthier planet. The WPC technology makes landfills obsolete and replaces Incineration as the primary process for WtE. The WPC technology already operates in three reference plants around the world and other three new commercial plants are under construction (two plants of 1000 tons/day in UK and a 650 tons/day in China), all three designed to convert municipal solid waste to electricity and district heat, in the most efficient and environmental-friendly manner. |
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Keywords: Plasma gasification, waste, energy.
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