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CFD analysis of thermal stress of a tubesheet
Vince, Tomáš ; Babička Fialová, Dominika (referee) ; Rebej, Miroslav (advisor)
This diploma thesis focuses on the phenomena of multiphase flow in a steam generator as a one of probable causes of tubes and tubesheet weld cracking. In the first part of the work, a research was carried out focusing on the boiling and the phenomenon of two-phase flow in technical applications, its characteristics and properties. The thesis continuous with an overview of available numerical multiphase models in the ANSYS Fluent 2021 R1 and a research of previously published works focused on two-phase flow with the presence of boiling. The research is followed by a description of the particular boiler, which is part of the nitric acid production plant in the chemical company DUSLO, a.s., its operating conditions and a more detailed description of the issue that is being addressed in this thesis. The second part of the work continuous with a description of the computational model, including a description of the geometry of the model and used simplifications, the computational mesh and the description of boundary conditions. Important part is the description of calculation setting of steady-state and transient CFD simulations in ANSYS Fluent. Finally, the results of the two-phase flow calculation are presented and then discussed in the conclusions.
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Refrigeration system with passive evaporator
Carbol, Marek ; Mauder, Tomáš (referee) ; Hejčík, Jiří (advisor)
This thesis is concerned with the design of a heat pump that does not use a ventilator during operation. In the introductory chapter, the functioning and the basic components of this device and other types of heat pumps are described. Properties of some commonly used refrigerants and oils as well as their classifications are stated. Due to the absence of a ventilator, a special heat exchanger was designed to achieve the required heat power. The choice of components in this refrigeration system takes into consideration the efficiency and functionality of the device.
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Heat flux calculation during boiling process – application for cooling of combustion chamber
Földváry, István ; Pačíska, Tomáš (referee) ; Vondál, Jiří (advisor)
There is a water-cooled combustion chamber at the Institute of Process and Environmental Engineering, which is used for testing of burners. Effective cooling is a particularly significant problem. It is also necessary to ensure accurate measurement of wall heat flux extracted by the cooling water. Therefore the main aim of the thesis is calculation of the minimum flow rate of cooling media required for safe operation of the combustion chamber. A comprehensive review of the heat transfer mechanisms was performed. Description is provided for the basic characteristics of phase changes with an emphasis on detailed analysis of mechanisms of boiling and evaporation. The presence of boiling at the water-side wall in the inner mantle was verified in the calculation part. Computation of the heat transfer coefficient was done by using the similarity methods. Temperature of the wall was then evaluated. A control on the presence of nucleate boiling was performed and the required minimum flow rate was determined for each section of the chamber.
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EVALUATION OF THE POSSIBILITY OF THE ORIGIN OF THE EXTERNAL SUFFOSION / HEAVE AND SOLUTION USING THE LIMIT STATE METOD
Hala, Mario ; Brouček,, Miroslav (referee) ; Bednárová,, Emilia (referee) ; Říha, Jaromír (advisor)
In the case of soil structures and/or subsoil of the water structures, filtration deformation can occur due to the effects of water seepage. One of the possible phenomena that can occur in water structures due to filtration deformation is external suffusion / heave, which ocure on the air side of the structure in the case of ascending external seepage, where soil particles are gradually subject to ascending seepage forces. The possibility of heave can be assessed using the method of partial factors, for which individual partial factors are needed, which are not specified in more detail in the literature. The aim of this work is to determine the partial reliability factor for failure due to heave based on the evaluation of laboratory experiments on uniform grain materials with non-uniformity number CU
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CFD analysis of thermal stress of a tubesheet
Vince, Tomáš ; Babička Fialová, Dominika (referee) ; Rebej, Miroslav (advisor)
This diploma thesis focuses on the phenomena of multiphase flow in a steam generator as a one of probable causes of tubes and tubesheet weld cracking. In the first part of the work, a research was carried out focusing on the boiling and the phenomenon of two-phase flow in technical applications, its characteristics and properties. The thesis continuous with an overview of available numerical multiphase models in the ANSYS Fluent 2021 R1 and a research of previously published works focused on two-phase flow with the presence of boiling. The research is followed by a description of the particular boiler, which is part of the nitric acid production plant in the chemical company DUSLO, a.s., its operating conditions and a more detailed description of the issue that is being addressed in this thesis. The second part of the work continuous with a description of the computational model, including a description of the geometry of the model and used simplifications, the computational mesh and the description of boundary conditions. Important part is the description of calculation setting of steady-state and transient CFD simulations in ANSYS Fluent. Finally, the results of the two-phase flow calculation are presented and then discussed in the conclusions.
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EVALUATION OF THE POSSIBILITY OF THE ORIGIN OF THE EXTERNAL SUFFOSION / HEAVE AND SOLUTION USING THE LIMIT STATE METOD
Hala, Mario ; Brouček,, Miroslav (referee) ; Bednárová,, Emilia (referee) ; Říha, Jaromír (advisor)
In the case of soil structures and/or subsoil of the water structures, filtration deformation can occur due to the effects of water seepage. One of the possible phenomena that can occur in water structures due to filtration deformation is external suffusion / heave, which ocure on the air side of the structure in the case of ascending external seepage, where soil particles are gradually subject to ascending seepage forces. The possibility of heave can be assessed using the method of partial factors, for which individual partial factors are needed, which are not specified in more detail in the literature. The aim of this work is to determine the partial reliability factor for failure due to heave based on the evaluation of laboratory experiments on uniform grain materials with non-uniformity number CU
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Refrigeration system with passive evaporator
Carbol, Marek ; Mauder, Tomáš (referee) ; Hejčík, Jiří (advisor)
This thesis is concerned with the design of a heat pump that does not use a ventilator during operation. In the introductory chapter, the functioning and the basic components of this device and other types of heat pumps are described. Properties of some commonly used refrigerants and oils as well as their classifications are stated. Due to the absence of a ventilator, a special heat exchanger was designed to achieve the required heat power. The choice of components in this refrigeration system takes into consideration the efficiency and functionality of the device.
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Heat flux calculation during boiling process – application for cooling of combustion chamber
Földváry, István ; Pačíska, Tomáš (referee) ; Vondál, Jiří (advisor)
There is a water-cooled combustion chamber at the Institute of Process and Environmental Engineering, which is used for testing of burners. Effective cooling is a particularly significant problem. It is also necessary to ensure accurate measurement of wall heat flux extracted by the cooling water. Therefore the main aim of the thesis is calculation of the minimum flow rate of cooling media required for safe operation of the combustion chamber. A comprehensive review of the heat transfer mechanisms was performed. Description is provided for the basic characteristics of phase changes with an emphasis on detailed analysis of mechanisms of boiling and evaporation. The presence of boiling at the water-side wall in the inner mantle was verified in the calculation part. Computation of the heat transfer coefficient was done by using the similarity methods. Temperature of the wall was then evaluated. A control on the presence of nucleate boiling was performed and the required minimum flow rate was determined for each section of the chamber.
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Numerická simulace separovaného dvoufázového proudění vařící se vody v kanálu o tvaru cívky
Novák, Aleš ; Hrubý, Jan
This work deals with a quasi-1D mathematical model of flow of a boiling liquid-vapor mixture in a coil-shaped duct heated from the outer side of the coil. The liquid and gas phases are allowed to flow at different velocities (stratified flow regime). The model simulates a modification of the laboratory steam generator built in Institute of Thermomechanics AS CR. The liquid is centrifuged to the heated wall thus enhancing the heat transfer. The model also includes heat conduction in the metal body of the steam generator.
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Nová laboratorní parní zkušební trať
Peukert, Pavel ; Hrubý, Jan
A novel laboratory steam test rig is being developed. It is intended primarily for the following purposes: i. development and testing of probes for sampling dry steam to determine heterogeneous nuclei in the steam, ii. study of liquid-vapor transport of admixtures in boiling, iii. study of heat transport in boiling and condensation processes, especially methods of heat transfer enhancement. The test rig allows accurate adjustment of the mass flow up to 0.25 kg per minute and adjustment of pressure up to 34 MPa and temperature up to 400°C. In the present stage, the pressure is limited to 4 MPa.
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