National Repository of Grey Literature 9 records found  Search took 0.00 seconds. 
Impact of Operation Parameters on Fine Combustion Particles Concentration in the Flue Gas of Biomass Boilers
Poláčik, Ján ; Masaryk, Michal (referee) ; Adamec, Vladimír (referee) ; Pospíšil, Jiří (advisor)
This work deals with the impact of operating parameters on fine combustion particles formation in the flue gas of biomass combustion device. The research part of the work describes the properties of fine particles, its basic division, impact on human health and the environment. The basic knowledge of the influence of biomass combustion process on fine particles production up to 1 µm in size is summarized. The main part describes the experimental setup for evaluating the size distribution of fine particles. The following section describes the experimental setup with measured results for various combustion parameters in laboratory combustion, automatic boilers, as well as in the manual wood-burning combustion device. The main parameters which were tested were combustion temperature, oxygen amount, type of fuel and geometry of the burned biomass. The impact of individual parameters on the formation of the fine particles is evaluated. The final part of the thesis summarizes the ways in which it is possible to significantly influence the emissions of fine particles by the appropriate choice of combustion operating parameters.
Thermoelectric Generators for Micro-CHP Units
Brázdil, Marian ; Navrátil, Jiří (referee) ; Masaryk, Michal (referee) ; Pospíšil, Jiří (advisor)
Small domestic hot water boilers burning solid fuels represent a significant source of air pollu-tion. It is therefore an effort to increase their combustion efficiency and to reduce the produc-tion of harmful emissions. For this reason, the operation of older and currently unsatisfactory types of household boilers has been legally restricted. Preferred types of boilers are low-emission boilers, especially automatic or gasification boilers. Most of them, however, in compar-ison with previous types of boilers, also require connection to the electricity grid. If there is a long-term failure in electricity grid, the operation of newer boiler types is limited. Wood and coal gasification boilers are currently available on the market and can be operated even in the event of a power failure, but only in heating systems with natural water circulation. In heating systems with forced water circulation, these boilers, fireplaces or fireplace inserts with hot-water heat exchangers cannot be operated without external battery supply in the event of a power failure. The dissertation thesis therefore deals with the question of whether it would be possible by thermoelectric conversion of waste heat of flue gases of small-scale low-emission combustion hot water domestic boilers to obtain sufficient electricity, to power supply their circulation pumps and to ensure operation in systems with forced water circulation independently of elec-tricity supply from the grid. In order to answer this question, a simulation tool predicting the power parameters of ther-moelectric generators was created. Compared to previously published works, the calculations and simulations include the influence of the generator on the boiler flue gas functionality. To verify the simulation tool, an experimental thermoelectric generator was built using the waste heat of the flue gas of an automatic hot water boiler for wood pellets. In addition to this genera-tor, there was also created an experimental thermoelectric fireplace insert and other equipment related to these experiments.
The Effective and Ecological Burning of Biomass
Špiláček, Michal ; Kolat, Pavel (referee) ; Masaryk, Michal (referee) ; Skála, Zdeněk (advisor)
This work deals with the creation of a numerical model of a biomass combusting chamber on a grate. The research part of this work describes the basic properties of biomass important for its combustion and the biomass combustion process itself. For this process which it is necessary to know the dynamics of the chemical reactions and the overall mechanism of a grate combustion of fuels. It also describes the production of harmful emissions that can be generated by combustion of biomass and the emphasis is mainly on the production of nitrogen oxides. In the next part is described the combustion device itself and the basic mathematical model which incorporates the mechanisms of heat transfer, flow of fluids and transport of chemical species. The basic mathematical model is then extended to a complete mathematical model by determining the initial and boundary conditions. Subsequently, the results of the computer simulation of the mathematical model are presented and commented. The main focus are the emissions of nitrogen oxides and hydrocarbons. These results are used to design an improvement of the geometry of the combustion chamber.
Development of Simulation Tool for Semi-Hermetic Compressor with the Objectives to Improve Efficiency
Tuhovčák, Ján ; Masaryk, Michal (referee) ; Pavelek, Milan (referee) ; Jícha, Miroslav (advisor)
Compressors are widely used across the all technical fields and current pressure on ecology increases the demand for more effective compressor with economical operation costs. The reasons for inefficiencies must be identified during the development process of a new compressor, where simulation tools might become very useful. There are many different tools for compressor analysis and choosing the right one is mostly dependent on the level of detail that must be analyzed. Models based on energy balance seem to be appropriate when the global parameters of a compressor are demanded. These models offer quick results with reasonable degree of accuracy in terms of basic compressor characteristics. The goal of this thesis is to develop such a simulation tool for a reciprocating compressor. The tool can predict compressor behavior based on compressor dimensions and valve properties. The processes inside the cylinder and heat transfer between the components of a compressor are analyzed using energy balance equation. Simulation tools were verified and experimentally validated using two different types of compressors, therefore they might be used for any reciprocating compressor under some conditions. Mathematical solution was developed in Matlab and therefore it is possible to add new sub-models or to couple the actual model with other simulation tools. This work also contains an analysis of heat transfer models used to predict heat transfer coefficient inside the cylinder and comparison with complex numerical approach. Impact of heat transfer on the compressor efficiency was evaluated too.
Heat Transfer Evaluation on Falling Film Tube Bundle
Kracík, Petr ; Masaryk, Michal (referee) ; Kořista, Milan (referee) ; Pospíšil, Jiří (advisor)
Sprinkled tube bundles with a thin liquid film flowing over them are used in various technology processes where it is necessary to separate the vapour and liquid phases quickly and efficiently. The process occurs predominantly at low temperatures with a corresponding decrease of pressure around the tube bundle. Such a technology is represented for instance by an evaporator at absorption units or an evaporator for sea water desalination. In ideal conditions water boils at the whole surface of an exchanger, but in practice it must be considered that in original spots of contact between water and the exchanger wall the water will not boil at the tubes' surface but the cooling liquid will merely be heated-up. The presented dissertation thesis focuses on this issue. The objective of the thesis was to determine the heat transfer coefficient at the surface of sprinkled tube bundles of various geometries at atmospheric pressure as well as low pressure. For this purpose experiments have been carried out at tube bundles consisting of copper tubes of 12,0 mm diameter placed horizontally one above another that were heated by water. Three types of tubes (smooth, sandblasted and grooved) of four various pitches (15,0 to 30,0 mm by 5,0 mm increments) have been tested. Simultaneously individual bundles' geometries consisted of 4, 6, 8 and 10 tubes with identical surface finish. Based on the conducted experiments the mathematical model of heat transfer that involves mainly analogy criteria has been made more accurate. A temperature field at the sprinkled tube bundle surface has been scanned by a thermographic camera during the performed experiments. Influence of geometry and tube surface finish on flow mode and consequently also on heat transfer has been assessed in accordance with the compiled methodology.
Control System of Building using Modelling and Simulation
Mohamad, Mohamad Kheir ; Ostrý, Milan (referee) ; Masaryk, Michal (referee) ; Štětina, Josef (advisor)
Udržovaní vnitřních klimatických podmínek tak, aby byly v souladu s tepelným komfortem lidí, je klíčovou otázkou pro řízení systémů vytápění, větrání a klimatizace (HVAC systémy). Počítačové modelování nabízí virtuální prostředí pro simulaci vnitřních i vnějších podmínek a s jeho pomocí je možné navrhnout řešení pro řízení technických zařízení budov. Tento proces vyžaduje pochopení těchto prostředí z fyzikálního a matematického hlediska tak, aby bylo možné fyzikální procesy daných prostředí prezentovat pomocí vztahů a rovnic odrážejících jejích různé parametry. Simulační proces dále nabízí možnost popsat interakci mezi těmito modely a jejich chování v čase, dává výchozí reprezentace těchto prostředí, a umožňuje pochopení jejich chování před přenosem těchto modelů do reálných aplikací. Simulace umožnuje respektovat, a ovlivňovat jejích chování přes kontrolu navržených modelů. MATLAB/SIMULINK software má pokročilé schopnosti pro simulace systémů HVAC, a to vytvořením širokého pracovního prostředí pro designéry v závislosti na vývoji matematických modelů a jejích simulace pomocí SIMULINK, aby výsledky mohly být slučitelné s požadovanými výstupy. Tato dizertační práce se zaměřuje na proces modelování vnitřního prostředí v budovách, aby bylo možné pochopit chování klíčových parametrů, které mají vliv na tepelnou pohodu obyvatel či uživatelů, matematické modely vnitřního prostředí posluchárny byly navržené speciálně pro tři základní parametry: koncentrace oxidu uhličitého, teplota vzduchu a relativní vlhkost. Změny chování těchto parametrů v průběhu času jsou simulovány a poté strategie kontroly návrhu těchto parametrů může je udržet ve vhodných rozmezích komfortních pro obyvatele či uživatele, i když změny venkovního klimatu, tepelné a hmotnostní zatíží interiér. Pomocí matematických metod, některé optimalizační metody byly navrženy za účelem snížení spotřeby energie bez vlivu na mezní hodnoty těchto parametrů. Proces validace modelu se provádí porovnáním výsledků s reálnými výstupy monitoringu Honeywell Enterprise Buildings Integrator systémem (EBI) nainstalován v areálu univerzity.
Coupling of the Models of Human Physiology and Thermal Comfort
Pokorný, Jan ; Masaryk, Michal (referee) ; Kratochvíl, Zdeněk (referee) ; Jícha, Miroslav (advisor)
The thesis deals with car cabin environment and thermal comfort inside. A car cabin heat load model was developed in Dymola/Modelica to investigate influence of ambient environmental parameters. The model was validated on the data set of eight test cases measured in a climatic chamber and in a real traffic. The main objective of the thesis was to develop a human thermal comfort model suitable for non-homogenous environments and for a car cabin environment especially. The Coupled model of human physiology and thermal comfort was developed in Dymola/Modelica. The model allows predicting an overall human thermal comfort from local boundary conditions representing ambient and personal factors. The model was validated by 16 test cases taken from experiments in literature. Moreover three test cases were created in Theseus-FE to consider an asymmetrical heat load from Sun rays inside a car cabin. Prediction of the Coupled model was compared with Fiala model and experimental data. The Coupled model predicted mean skin temperature for moderate activities in neutral and warm environment well. In cold environment a predicted core temperature was very affected by ambient temperature and during high activity exercises, the predicted mean skin temperature was too high.
COMPUTING SOFTWARE AND METHODOLOGY DEVELOPMENT FOR REFRIGERATION MINICHANNEL CONDENSER EVALUATION
Pavlů, Jaroslav ; Masaryk, Michal (referee) ; Jaroš, Michal (referee) ; Pospíšil, Jiří (advisor)
Air cooled heat exchangers are used in many technology applications. Compactness, functionality and prize is decision maker for many future customers. Current development of compact heat exchangers is evident. Mostly used technology - expanded copper tube on aluminium fin is fluently changed by all aluminium heat exchangers with sophisticated heat exchange surface. Heating, Ventilating and Air-Conditioning with Refrigeration industry (HVAC-R) uses more and more extrude aluminium profiles as the main structure for all size heat exchangers. Similarly to Automotive industry HVAC-R uses minichannels as the basis of their products. It is not a new technology, it is technology proved through many years use in car industry. It is also true that current well known minichannel technology is not the last step. New designs and production lines are currently developed as well. All these new technologies have one unsolved thing together – how will be the new technologies easily computed through models. Current correlations which were used till now are obsolete, because of system miniaturization mainly. It is not easy to adapt old macro channel correlations on minichannel or microchannels where is not possible to diminish capillarity effects, different flow structures, etc. All these difficulties causes in model changes, software changes or iterative procedures upgrades. It is also evident that a lot of experimental exercises have to be done to examine heat exchanger behaviour ad characteristics. Because of precise computation of minichannel heat exchangers need or its geometry optimization is dissertation theme aimed to compare computation methodologies. PhD thesis is also aimed to check functionality of proposed computation system used simple similarity model. All proposed methods are compared to experimentally measured data and as the outcome of thesis are these data used to develop new computation basis.
Optimization of Cabin Environment in Small Transport Aircraft
Fišer, Jan ; Janotková, Eva (referee) ; Masaryk, Michal (referee) ; Patočka, Stanislav (referee) ; Jícha, Miroslav (advisor)
The thesis deals with design and optimization of environment in cabins of small transport aircrafts, especially in terms of thermal comfort and quality of ventilation. The design of air distribution systems and structural design were optimized and most important parts of cabin design with highest impact on the quality of thermal comfort and ventilation were identified based on literature research and experience of the author. The chosen modifications and their influence on the microclimate inside the cabin were investigated using the CFD model, which was validated by results obtained from measurements of flow and temperature fields in the cabin mock-up of small transport aircraft EV-55. Next optimizations were investigated: The type of air distribution system, The geometry of ducts of air distribution system, Thickness of thermal insulation and Emissivity of internal surfaces. Thermal comfort was assessed based on the methodology of the equivalent temperature and comfort zones diagram developed by H. O. Nilsson and for assessing the quality of ventilation the concept of based on index of the age of the air was used. Fifty cases were simulated in total and base of its results Modified mixing ventilation with original air ducts geometry have been evaluated as an optimum. The ducts geometry of Modified mixing ventilation system was suggested by author specially for the thesis. In combination with high thermal insulation of walls and high emissivity of the interior, then this system of ventilation ensures maximum thermal comfort and quality of ventilation for the investigated range of environmental and operational conditions.

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