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Development of a mathematical model of deaeration of superheated water when it hits the rarefaction zone

Yu.E. Barochkin, G.V. Ledukhovsky, V.P. Zhukov, S.D. Gorshenin

Vestnik IGEU, 2018 issue 5, pp. 5—11

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Abstract in English: 

Background. Removal of dissolved gases by boiling superheated water, when it enters the rarefaction zone, called the initial deaeration effect, proceeds as a concomitant process in various types of heat and power equipment: dilators of condensates and purging water, steam condensers, and some types of heaters. There are also deaeration devices, whose principle of operation is based on the initial deaeration effect: cavitation-jet, centrifugal-vortex deaerators, drop deaerators of superheated water. The contribution of the initial effect to the overall deaeration efficiency, according to the published data, can reach 80 %, so it must be taken into account when calculating the equipment in question. However, at the present time there are no mathematical models that could calculate the initial deaeration effect with an accuracy acceptable for solving practical problems. All this makes it necessary to study water deaeration process in the considered conditions and to develop suitable mathematical models.

Materials and methods. We have used methods of thermodynamics, theory of similarity of heat and mass transfer processes, regression analysis, mathematical statistics, as well as published experimental data on the process of water deaeration due to the initial effect in deaeration devices of various types.

Results. Based on the existing mathematical model of phase transition in a superheated liquid and obtained experimental data, we have developed a closed mathematical description of deaeration of superheated water when it enters the rarefaction zone by using methods of the theory of similar heat and mass transfer processes. It has been found that the main factors determining the efficiency of water deaeration under the considered conditions are: decrease in water temperature in the device, initial water overheating relative to the saturation temperature, and hydraulic loading of the device.

Conclusions. The proposed mathematical description makes it possible to calculate the effectiveness of the deaeration effect with an accuracy that is acceptable for solving practical problems, which allows us to recommendit for use in the design and adjustment of heat and power equipment.

References in English: 

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Key words in Russian: 
термическая деаэрация, начальный эффект деаэрации, перегретая жидкость, десорбция растворенного кислорода, деаэрационное устройство, центробежно-вихревой деаэратор, кавитационно-струйный деаэратор, капельный деаэратор, математическая модель, фазовый переход
Key words in English: 
thermal deaeration, initial deaeration effect, superheated liquid, desorption of dissolved oxygen, deaeration device, centrifugal-vortex deaerator, cavitation-jet deaerator, drop deaerator, mathematical model, phase transition
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