|
|
Cooling Concepts in Power Electronics
Hőhn, Matěj ; Súkeník, Jakub (referee) ; Toman, Marek (advisor)
This bachelor thesis deals with cooling concepts in power electronics and experimental measurements of thermal resistances in two different fan-cooled heat sink samples. In the first part of the thesis, calculations of losses in semiconductor switching devices are described. These are losses due to current conduction and switching between operating states. Then the basics of heat transfer theory such as conduction transfer, convection transfer, radiation transfer, and thermal-electrical analogy are described. In the third section, the procedure for calculating the required thermal resistance of the heat sink is described. Then, cooling concepts in power electronics are described, which include basic types of heat sinks, fan-cooled cooling and its operating characteristics, heat pipes, thermoelectric cooling and the use of liquid systems, such as cold plates and boiling liquid cooling. The last part of the thesis describes the preparation of a laboratory workstation for measuring the thermal resistance of two different fan-cooled coolers and comparing the measured results.
|
|
|
Sleep quality depending on room environment
Veličková, Kateřina ; Pokorný, Jan (referee) ; Fišer, Jan (advisor)
The aim of this diploma thesis was to determine the thermal resistance of selected sleep assemblies (clothing, mattress, blanket, pillow) using measurements with a thermal manikin and subsequently to determine the appropriate ambient temperatures at which a balanced thermal equilibrium between the sleeping person and their environment would be maintained. Four different assemblies were selected for measurement purposes, differing in the type of blanket used (summer blanket, quilt, cover, and no blanket). The influence of the thermal manikin's position on the measured value was also investigated. It was proven that the influence of position on the overall thermal resistance is negligible, with measured values ranging from 1.12 clo (assembly without a blanket in the side position) to 2.05 clo (assembly with a summer blanket in the back position). Subsequently, appropriate ambient temperatures were determined using the PMV model, which ranged from 24.4 °C to 28.6 °C. The two-node model proved to be insufficiently sensitive for the addressed issue, and the heat flux maps derived from the equivalent temperature model were not calibrated for sleep but for mild activity while seated. Nevertheless, they provided interesting information about the perception of thermal comfort in different parts of the body.
|
|
|
Study of the thermal insulation effect of thermally reflective insulations
Skříček, Darek ; Vala, Jiří (referee) ; Čermák, Jan (referee) ; Šťastník, Stanislav (advisor)
The dissertation on the topic Study of the thermal insulation effect of thermally reflective insulations is focused on the issue of measuring the thermal resistance R of thermoreflective insulations and determining the most suitable layer with the best thermal insulation properties. By measuring thermoreflective insulations on the Hot-Box measuring chamber, it was proven that higher values of thermal resistance R are always achieved with aluminum foil, which has the highest possible reflection of the radiant component of heat, i.e. the lowest possible emissivity on the surface. For this reason, the reflectance was measured on the Mid-IR Integrat IR ™ measuring apparatus. To study the thermal insulation effect of thermoreflective insulations, ten samples of these insulations with different compositions of aluminum and bubble foils are used to measure the insulation properties. The suitability of using thermoreflective insulation for building insulation was proven by measuring these foils.
|
|
|
Study of utility properties thermal-reflective insulations in the buildings
Holeček, Dominik ; Skříček, Darek (referee) ; Šťastník, Stanislav (advisor)
The diploma thesis is partly dedicated to energetic efficiency of buildings and describes possibilities how to evaluate energetic efficiency of buildings in the Czech Republic. We also get to know with distribution of thermal insulators by material base and use in construction. There are also mentioned methods how to determine thermal insulations characteristics of heat insulations, so called heat conductivity coefficient. The last and the crucial chapter of theoretic part is dedicated to thermal-reflective insulations. There are mentioned some of the basic characteristics of insulations, material composition and heat transfer mechanism in their structure as well. Practical part describes measurement of thermal resistance of chosen samples of thermal-reflective insulations per measuring device on the principal of Hot Box method. In the next step was determined emissivity of aluminium foils which forms the surface of chosen samples of thermal-reflective insulations. In the end of thesis are defined possibilities of use thermal-reflective insulations in building structures especially in passive and low-energy buildings in climatic conditions of the Czech Republic.
|
|
|
Calculation of thermal resistance of finned heatsink
Kyanka, Radim ; Huták, Petr (referee) ; Toman, Marek (advisor)
This bachelor's thesis is focused on the problem with analytical calculations needed to define thermal resistance of finned heat sinks. First it describes how temperature proceeds at different boundary conditions at fin tip. Than it describes different mechanisms of heat transfer, equlation of heat resistance especially of natural and forced convection. To verify the results there is comparison between analytical equlations written in Matlab program and measuring results.
|
|
|
Operational Parameters of LED and their Modelling
Pavelka, Tomáš ; Novák,, Tomáš (referee) ; Gašparovský, Dionýz (referee) ; Baxant, Petr (advisor)
Doctoral thesis deals with parameters of LED light sources and their static and dynamic changes due to variable operational conditions. Firstly there is briefly described the history of light emitting diodes, that brought LED from unintentional observation of luminescence to light source, which is generally used through the whole area of lighting techniques. Thesis focuses on light parameters analysis, which are specific for semiconductor light sources and their mutual relations. These relations in compliance with understanding the principles of light emission in semiconductor light sources enable establishing of basic connections and effects usable for LED behaviour model. Mutual relations of LED parameters and influencing factors are verified by measurement of chosen testing samples. For deeper understanding of diode parameter influencing mechanisms there are analysed current degradation models including degradation of partial components. On the basis of these facts there is created a model of LED luminaire operating with LED parameters together with cooling system that represent the integral part of the luminaire. Impact of supply drivers is also studied, because they are necessary for LED operation. Designed model supports the area of static changes of light parameters, as well as the dynamic changes of output parameters. Presented model is verified by testing measurements at basic operational states and partially outside of the common operational limits. There are also presented the possibilities of real use of the model that involve the evaluation of designed luminaire for specific light sources, searching for optimal operational limits, optimization of luminaire heatsink or using public lighting systems for regulation of electricity grid load fluctuations.
|
|
|
Primary School
Forman, Daniel ; Manová, Ludmila (referee) ; Maceková, Věra (advisor)
Thesis Theme is a primary school, namely the outbuilding primary school Havlíčkův Brod, Konečná 1884. I suggest first grade pavilion and pavilion with school canteen with kitchens. Pavilions are based on the footings. Pavilions are designed as a two-way system from the wall HELUZ. Construction of ceiling are from ferroconcrete slabs are cross reinforced, single-layer roof is flat with a classic sequence of layers. In addition to construction and process layout I solved also the statics of building in specialize of concrete structures. The following are also evaluated heat and acoustic requirements and requirements for fire safety of buildings. New pavilions are solved as wheelchair accessible. Pavilion of the first grade has two floors with 5 classes of stem, 1 vocational and 2 classes are earmarked for after-school clubs. This pavilion is connected to the connecting neck between the former pavilon A and pavilion B. Dining pavilion has one floor, which is divided in the school canteen and kitchen is connected to the connecting neck leading to the gym. The land is mildly sloping to the south side. All consstructions comply with the applicable standards and recommendations ČSN.
|
|
|
Optimization of the printed circuit board for power LED
Schenk, David ; Klíma, Martin (referee) ; Ing. Josef Vochyán, Ph.D., ALCZ Jihlava (advisor)
This diploma thesis deals with the problems of heat transfer on printed circuit boards. The first part consists of a theoretical analysis of the principles of conduction of heat in different environments, comparing the properties of common type’s base materials for PCBs in terms of thermal properties and focuses on heat transfer from the chip. In the following part they are general information about the program ANSYS ® Workbench ™. Next part consists of the basic designs of PCBs and their improving. PCBs thermal properties for different configurations are verified with calculations, simulations and practical measurements. In the last part there are created design recommendations for PCBs design based on the comparison of the results of initial proposals and proposals to improvements.
|
|
|
Design of synchronous linear motor thermal network
Čech, Jan ; Toman, Marek (referee) ; Knebl, Ladislav (advisor)
The first part of this thesis deals with the study of linear motors. The introduction of the thesis deals with the brief description of the linear motor, including its accessories. This part explains principle of linear motors, their general advantages and disadvantages. The next section contains an overview and division of the currently used linear motors. The second part deals with the theoretical description of forms of heat transfer. The third part of the thesis deals with the design of an equivalent thermal circuit model of a linear iron-core linear motor with permanent magnet. Hereafter, the proposed design will be used to calculate the temperatures of the individual motor units. The temperatures are later compared with the results obtained with finite element method.
|
|
|
Sports complex
Touš, Jakub ; Pobořil, Lukáš (referee) ; Petříček, Tomáš (advisor)
The main focus of this thesis is to design the expansion and modernization of a sport complex "U Jezu" for a sport club TJ Roztoky. This thesis is consisted of a study for a territorial agreement. In this study, there are indicated a formation of two playing fields with the artificial surfaces, beach volleyball court proposing two building objects as a base for the entire complex, which consists of garages, storages and a main building. A more detailed design was created for the main building. As the supporting structure of the object, the transverse wall system completed with outdoor columns supporting the cantilevered portion of the ceiling tiles, which are mainly unidirectionally reinforced concrete floor slabs. The supporting structure is based on the strip foundations. The designed building object has two-above ground floors and a ground floor, which will be created by embedding the building object into the hill side. The ground floor is designed for the relaxation and the leisure purposes. Moreover, there is also a technological equipment necessary for the operation of the facility. On the first above ground floor, there are designed locker rooms for athletes, a club room with a kitchen and an accommodation unit for a manager of the complex. The second floor is for the accommodation. There are designed rooms with lounge and office of the president of the sport club. Part of the second floor consists of a terrace. For the roofing, a flat roof with a single-classic sequence of layers is designed. In this thesis, the static is partially solved. Furthermore, the object is evaluated in the terms of lighting, acoustic and thermal requirements as well as requirements for the fire safety of buildings.
|
guest ::
