Thesis for the Degree of Doctor of Sciences in specialty 01.04.14 – Thermophysics and Theoretical Fundamental of Thermal EngineeringKey words: heterogeneous medium, stochastic structure, combustion wave, percolation theory, high temperature heat transfer.
The aim of research: is determination and explanation of influence of heterogeneous media microstructure.
Research methods:Monte-Carlo technique, computer modeling, kinetic equations, percolation theory, the methods of fractal geometry, the methods of experimental thermal physics.
The results and their novelty. For the first time correlation has been obtained between fractal properties of percolation cluster and distribution of finite clusters by size near the percolation threshold. The influence of fluctuations of reagents spatial distribution during solid mixture combustion on limits of combustion wave propagation has been established and described. The existence of common energetic limit of extinction in heterogeneous systems has been theoretically predicted and proved experimentally. For the first time the existence of two regimes of combustion wave propagation - fast and slow - through heterogeneous mixture of reagents diluted by inert filler has been experimentally observed and theoretically explained. For the first time correlation between irremovable in real systems non-ideal mixing of powders in binary mixtures and observing in experiments shift of maximal velocity of combustion front out from the components stoichiometric relation has been founded. The combustion statistic model of mixture of solid fuel particles in gaseous oxidant has been developed. It takes into account the stochastic spatial distribution of solid particles and it allows for the first time to describe the experimentally observed shift of maximal velocity of combustion front into area of gas mixture enriched with fuel.
The existence of minimum of effective thermal conductivity of fiber materials at definite density and high temperatures has been observed experimentally.
The results obtained can be used for development of high temperature furnace equipment, synthesis of new materials in combustion wave, enhance of effectiveness of solid fuels burning.
Hemmasian Kashani Mohammad Mehdi
Keywords: numerical simulation, cooling tower, heat and mass transfer, thermal efficiency.
The Object of investigation is natural draft cooling tower, systems of aerodynamic flow control, cooling systems and heat exchangers.
Subject of research is thermal efficiency of natural draft cooling tower, the processes of heat and mass transfer in the tower, including the interphase heat and mass transfer, aerodynamic interaction between gas flow inside the cooling tower and the wind in the conditions of utilization of flow control design elements.
The aim of the study is to determine method that increase thermal efficiency of cooling towers, hydrodynamic optimization of cooling towers.
The methods of research: numerical simulation.
The scientific novelty: For the first time the effect of internal flow rotation in over-shower zone on heat and mass transfer and flow field of over-shower zone was studied. This investigation show that internal flow rotation increase homogeneity of internal flow field and improve heat and mass transfer. The effect of application of different design elements on efficiency and air mass flow rate of natural draft cooling tower subjected to cross-wind is investigated numerically. Three types of flow control elements (blade deflector in over-shower zone, deflectors in inlet window and windbreak walls in rain zone) were modeled. Comparative efficiency of natural draft cooling tower as a function of the parameters of the above-mentioned design elements was analyzed.
Field of application: the obtained results can be used for basic design of natural draft cooling tower and efficiency improvement of natural draft cooling tower under cross-wind. The model have ability to predict and simulate behavior of cooling tower under different ambient conditions. Optimization of natural draft cooling tower design parameters may be performed.
Thesis for the Degree of Doctor of Philosophy in specialty 01.04.14 – Thermophysics and Theoretical Fundamental of Thermal EngineeringKeywords:recovery, organic pollutants, porous media, volatile organic compounds, visbreacking, filtration combustion.
Цель диссертационной работы: установление основных закономернос- тей топочного процесса при сжигании твердого биотоплива в циклонно- слоевой топочной камере.
The object of this research is heat and mass transfer processes associated with utilization of organic pollutants of liquid, solid and gaseous substances by method of filtration combustion and heat recirculation, as well as systems and apparatus (reactors) of substances recovery utilizing filtration combustion, technical systems for control of the thermal and gasdynamic conditions, gas supply and combustion initiation.
Research subject - thermal and physic-chemical peculiarities of phase and chemical transformations during the process of purification of inert substances by means of filtration combustion, experimental modeling of combustion of organic components of liquid, solid and gaseous substances.
The thesis is dedicated to development of new and optimization of existing oxidation methods of organic pollutants in inert materials by using filtration combustion; to experimental modeling of processes of filtration combustion of organic components of liquid, solid and gaseous substances by the method of filtration combustion in porous media.
The methods of research: experimental investigation.
The scientific novelty: The new methods and schemes of apparatus for recovery of solid dispersed, liquid and gaseous substances recovery from pollutants are worked out. Which let one reduce pollutants content down to concentrations 20-50 times lower occupational exposure limit, by utilizing organic pollutants as a fuel for the process.
For the first time the method and apparatus for oil visbreaking is created utilizing filtration combustion. Which let one reduce viscosity of viscous oils up to 10 times and non-viscous oils - up to 2 times and utilize row oil as a fuel for the process.
Field of application. All the created and patented methods and apparatuses let one effectively recover polluted water, solid sorbents, gases from organic pollutions as well as implement oil visbreaking process by utilization of the row oil as a fuel. There are two acts of practical application of results of the work in industry.
Khodyko Yuliya Andreevna
Thesis for the Degree of Doctor of Philosophy in specialty 01.04.14 – Thermophysics and Theoretical Fundamental of Thermal EngineeringKeywords: evaporative cooling, colloidal precursors, supersaturation, coalescence, Brownian diffusion, thermophoresis.
The object of study - micron droplets and nanoparticles formed by the evaporative cooling of the droplets.
The subject of the study - the processes of heat and mass transfer in evaporative cooling of micron droplets.
The aim of the thesis - a theoretical study of heat and mass transfer in the preparation of nanoparticles by spray pyrolysis of micron droplets under low pressure. The method of research - mathematical modeling.
Obtained results and their novelty.
For the first time a set of models has been developed which allowed to explain the physical picture of the formation of nanoparticles from micron droplets of solutions under low pressure. It was revealed that, due to evaporative cooling of micron droplets, the supersaturated solution is formed inside them and nanoparticles grow due to precipitation of dissolved substances on colloidal precursors originally located in the droplet. It was shown that the final morphology of an ensemble of nanoparticles is determined by three processes - coalescence, Brownian diffusion and the rate of evaporation. The quantitative study of the influence of coalescence on the evolution of the size distribution function of nanoparticles was carried out. It was shown that the Brownian diffusion and slow droplet evaporation determine the morphology from the identical spherical nanoparticles, and the morphology of the «hollow» type is formed in rapid droplet evaporation when the Brownian diffusion has no time to uniformly distribute nanoparticles over the droplet volume, and they are concentrated near the surface. It was revealed that in high-temperature flow reactor the moving micron droplets are heated no more than by 20 К due to the evaporative cooling process.
Efficiency: The developed models enabled to simplify the design of the apparatus for producing nanoparticles from droplets of solutions and to improve its energy efficiency compared with foreign counterparts.
Field of results application: the calculation of the optimal parameters and devices for the production of nanoparticles.
Key words: solid biofuel, cyclone-bed combustion chamber, the coefficient of excess air, concentration, carbon monoxide, nitrogen monoxide, bottom blowing, tangential blowing, fuel bed.
The aim of the thesis: establishment of the main regularities of furnace process when burning solid biofuel in the cyclone-bed combustion chamber. Methods of research: in conducting the experiments were used: the pneumatic method of measuring the pressure and velocity, contact methods of temperature measurement, the electrochemical method of gas analysis. Summary of the main parameters of the swirling flow is performed based on the similarity theory of hydrodynamic processes. The methods of the theory of heat and mass transfer were used with development of methods for calculation of the velocity particles and active thermal insulation.
The obtained results and their novelty: for the first time the features of the hydrodynamics of a cyclone (cyclone-bed) chamber have been investigated when entering the tangential and bottom blowing, including the presence of granular bed on gas distributor. The modes of one - and two-phase flows were described. The equations for the calculation of the basic characteristics of a vortex flow are obtained. For the first time the features of burning of solid biomass fuels (wood, peat and their mixtures) in cyclone-bed combustion chamber are studied. Identified limits moisture content of wood chips and peat mass content in a mixture of «peat-wood chips» (moisture content per wet mass fuel - 45%, the share of bottom blowing - 50%) in which there is an unstable combustion. The temperature distribution in the cyclone- bed furnace depending on the fuel type and moisture content was set. The dependence emissions monoxides of carbon (CO) and nitrogen (NO) in exhaust gases from air excess, the diameter of the outlet, the share of the bottom blowing and capacity of the furnace during combustion chunks wood and crushed peat briquettes are studied experimentally. It was revealed that the organization of flow swirling in the combustion chamber to reduce the excess air ratio in comparison with straight- through grate furnaces. The effective scheme of active thermal insulation of furnaces were offered and the methods of its calculation were developed. The methods for calculation of the velocities of the small particles in the vortex chamber on the basis of the values of velocities of the gas was developed.
The degree of use: on the basis of the results of the study have been developed the technical documentation on the prototypes of the water-heating boiler capacity of 0.5 MW, equipped with a cyclone-bed furnace and the cyclone-bed furnace with fluidized bed capacity of 9 MW.
The field of application: power engineering, construction of the furnace installations for the combustion of solid biofuels.
Keywords: arc plasma torch, plasma furnace, heat transfer, waste processing, combustion, heat calculation.
Aim of research: determination of dependence of heat transfer parameters on thermotechnical characteristic of plasma low from plasma torch; development of method of plasma furnace thermal design and its application for reconstruction of complex of waste processing that is produced as a result of nuclear power station operation.
Method of investigation: experimental-statistic investigation thermal physics processes in plasma furnaces for waste processing and plasma torches. For the reason of thermal parameters measurement special automation complex was used. Development of methods and heat calculation of process of heat transfer in plasma furnaces was done
Obtained results and their novelty: Parameters of operation of plasma shaft furnace with electric power up to 100 kW (capacity up to 100 kg/h) were obtained. The dependence of Nusselt number vc function of specific flux of pulse that is carried in chamber by plasma flow was determined. Method of heat calculation of plasma furnace was designed. Recommendations for two chamber plasma furnace for low and intermediate level radioactive waste modernization with the purpose of exhaust gas afterburning and decreasing loading of gas cleaning system. The furnace is placed at Smolensk nuclear power station. DC arc plasma torch (power 50 kW) was modernized.
The rate of results use: plasma torch PDS50-03 is used in plasma furnace for radioactive waste processing at Complex of solid radioactive waste processing at Liquid and solid radioactive waste storage (LSWS) at Smolensk nuclear power station (SNPS). Results of heat calculations and recommendation for two chamber plasma furnace modernization ware used for design of project of reconstruction of Complex of solid radioactive waste processing LSWS SNPS.
Field of application: design and development of processes and apparatus for different kinds of waste (including low and intermediate level radioactive waste) processing with thermal plasma.
Keywords: thermal pump, refrigerating machinery, coolant, optimisation methods, heat exchange
The purpose of dissertational work: increase of efficiency of design and operation in off-design modes of steamcompressive transformers of heat on the basis of joint calculation of loop variables and heatexchange devices of a contour taking into account pressure losses in elements.
Research methods: mathematical modelling with carrying out of the computing experiment on the basis of the developed package of applied program.
The received outcomes and their novelty: the complex method of numerical analsis of steamcompressive working in stationary and non-stationary modes transformers of heat was developed. The method was realised in the form of the package of applied programs and allows to carry out the interfaced calculation of loop parameters and heat exchange equipment with taking into account irreversible losses, including ones in contour pipelines. On the basis of the computing experiment the specified data of the influences of pressure losses on the power efficiency of the considered thermal pumps, and also influence of the auxiliary heat exchange devices on the power characteristics of the refrigerating machinery were obtained with taking into account the work of the basic heat contour exchangers. The efficiency of cycles data of heat transformers with ozone-safe coolants were obtained. The area of optimum regime and constructive parameters of the heat transformers was revealed with taking into account the optimisation of air free-convective heat exchange devices of the contour.
Efficiency: the research results were used in at the in laboratory of properties and technologies of energycarriers (working environments) and the reference with a radioactive waste of JIPNR-Sosny of the National Academy of Sciences of Belarus at choice of powereffective coolants and implemented in the academic process at Belarus State Technological University. Results are used on CJSC «Oktyabrskhimmash>> at evaporator design with the bimetallic ridge pipes and on OJSC «LENNIICHIMMASH» when developing the evaporator of the thermal pump working in a mode of free convection
Field of the results applying: working out and designing of the power-efficient refrigerating machinery, thermal pumps, combined installations.