MASTER'S THESIS
on a theme:
"Optimization of operating characteristics
of low temperature heat-exchangers"
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Actuality
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Increase of consumption of fuel in connection with the wear of present power equipment, and also gradual and continuous his rise in prices causes the necessity of perfection of processes of burning, and also processes of utilization of heat of gaseous products of combustion. The common increase of economy of boilers is the vital task of energetic.
The increase of economy of technological process on modern power-stations is arrived by many ways. One of them, becoming usual for energy, consists in the use of heat of gaseous products of combustion for warming up of air, necessity for combustion of fuel. Warming up is carried out in air heaters. It is gas-to-gas heat-exchangers set in chimney of boiler.
The basic problem of exploitation of air heaters is low temperature corrosion of surfaces of heating. Corrosion is related to besieging on-the-spot, having a temperature below than the point of dew, sulphur and its combinations. Because of it, there is limitation on the range of working temperatures of air heater (70-110° C).
In connection with aforesaid, it is suggested to replace traditional tubular air heater on a similar device with intermediate heat-carrier and use of thermal pipes (thermosiphons). This operation will allow to localize corrosion of surfaces of heating, and to decrease its intensity on the whole due to diminishing of amount of pipes getting in corrosive dangerous area.
It prolongs longevity of work of air heater and the same reduces expenses on his exploitation (including permanent repairs).
Finally, for the increase of efficiency of the use of heat of products of combustion, it is planned to conduct optimization of the set device with the purpose of maximization of his thermal efficiency.
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Review of the executed works
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The huge amount of works is devoted to problems of optimization. In particular huge amount of books of Kafarov V.V. in the field of modelling heat-exchange and chemical processes, optimization heat-exchange processes, etc.
Separate attention is deserved by works of Kalafati D. are publications in collections of the advanced studies and technical magazines, optimizations of arrangement of pipes bunches sacred to the tasks, and also book, "Optimization of heat-exchangers on efficiency of heat exchange".
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Purpose of work
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The decision of task of receipt of maximal amount of heat transferable from gases to air by determination of optimum arrangement of air heater in chimney of boiler is the purpose of this work.
The amount of transferrable heat is limited to the value of the maximum thermal stream determined by the crisis of heat emission at the bubble boiling.
The value of this size concernes depending on thermophysical descriptions of products of combustion and air, parameters of work of boiler aggregate, geometrical descriptions of air heater and parameters of arrangement of pipe bunch in chimney of boiler.
Expression of amount of heat through the indicated descriptions is functional, search of ekstremum of which there is the basic task of this work. This task decides with the use of extreme methods for the tasks of optimization.
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Literature
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1. Иоселиани А.Н. и др. Методы оптимизации параметров теплообменных аппаратов АЭС. - Мн.: Наука и техника, 1981. - 144 с
2. Калафати Д.Д., Попалов В.В. Оптимизация теплообменников по эффективности теплообмена. - М.: Энергоатомиздат, 1986. - 152 с
3. Демидович Б.П., Марон И.А. Численные методы анализа. - М.: Наука, - 1967 г.
4. Пиоро И.Л. и др. Эффективные теплообменники с двухфазными термосифонами. - Киев: Наукова думка, 1991. - 248 с
5. Васильева С.А., Илющенко В.И., Гаркавый Е.Я. Устройство автоматического управления индивидуального отопительного прибора - "Автоматизація технологічних об'єктів та процесів. Пошук молодих. Збірник наукових праць VI Міжнародної науково-технічної конференції аспірантів та студентів в м. Донецьку 24-27 квітня 2006 р." - Донецьк, ДонНТУ, 2006 - с. 200-202.
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