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Analysis of effect of solar radiation concentration on the thermal insulation degradation in the flat roof construction
Židek, Ondřej ; Běžel, Jakub (referee) ; Žák, Antonín (advisor)
The master´s thesis analyzes influence of direct and reflected solar radiation to heat strain and degradation of thermal insulation in the flat roof construction. In many building was a problem in a significant degradation of thermal insulation made from expanded polystyrene in the vicinity of glass surfaces. To determine the causes of this problem, it was necessary to study and test the properties of building materials and the physical nature of the effect of solar radiation on the building structure. In the introductory section lists the cases of buildings with degradation of thermal insulation and existing knowledge on this issue. The theoretical part describes the technical properties of thermal insulating materials used in the flat roof construction, nature and division of solar radiation, optical laws of light reflection and physical theory to explain the technical thermal behavior of building materials and structures. The last part describes a practical model and analyzing measured data in thermal stress in the flat roof construction. The practical part also determines the importance of different influences configuration structures using to dynamic simulations. At the end of the practical part they are validated theoretical knowledge obtained by analyzing data from a practical model.
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Thermal conductivity measurements
Sklenář, Milan ; Bejček, Ludvík (referee) ; Beneš, Petr (advisor)
This thesis focus on measurment of thermal conductivity by transient point heat source method and heat diffusion through materiál. There is described exemplar, measurement procedure and used devices. Thesis focus on verification of teoretical equations and effects of variables, which can affect accuracy of measurement.
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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.
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Study of the behavior of insulating materials in a high humidity environment
Havelka, Jindřich ; Peterková, Jitka (referee) ; Zach, Jiří (advisor)
Extruded polystyrene (XPS) is presented as non-absorbent material and it is applied in building construction with high moisture, such as inverted roof. The reason for that is a very good ratio of thermal and mechanical properties and it is used in moisture-loaded applications due to the closed pore structure and high diffusion resistance factor, which are declared by the manufacturers. Long-term experience and studies show that XPS accumulates moisture during long-term exposure in an environment with high humidity. A long-term water absorption test at full immersion for 84 days has been proposed to better illustrate the trend of increasing water absorption. A total of 6 products from different manufacturers that are recommended for inverted roof application, were tested. All tested XPS products have reached high amount of water absorption. The main goal was to map the real properties of XPS at high humidity loads. It was found that each product showed a different degradation of thermal conductivity at the same volume moisture value. Furthermore, there was found the connection between the surface structure and amount of water absorption. Products with waffle structure had higher humidity than products with a fine structure.
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Validation options for increasing the thermal insulating properties of foam plastics
Smutný, Vojtěch ; Kopřivík, František (referee) ; Šťastník, Stanislav (advisor)
The thesis is devoted to the study of material properties of selected types of polystyrene, especially expression of the coefficient of linear thermal expansion. The work contains two main chapters, theoretical and practical. The theoretical part of the thesis deals with an overview of the thermal insulation in the Czech Republic, the description of phenomena related to heat transfer mechanisms and an overview of experimental methods for determining thermal insulating properties. The practical part presents results of measurements of samples with foamed polystyrene, which is modified by the addition of selected substances. The thesis describes the machine program, which is used to calculate the temperature in during the construction arrangement under the sunlight load.
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Temperature measurement in electric machines
Halfar, Ivo ; Huzlík, Rostislav (referee) ; Janda, Marcel (advisor)
The bachelor's thesis Temperature measurement in electric machines deals with beginning and exuding of the heat of electric motors and measuring of the temperature. The temperature is one of the most important values in diagnostic. High temperature could damage an isolation and it could tend to destroy of the whole machine. The temperature influences their magnetic properties on motors with permanent magnets. If you reach the Curie temperature it could come to its demagnetisation. Measuring of the temperature is important to verify allowable warming of motor or more precisely its spooling. The measuring of the temperature is needed for making motors with minimum of charges and its worth at the end. We could use two methods for measuring the temperature. It is contact and noncontact method. Warming and decomposition of the temperatures it is possible to appoint also with help of theoretic computations which are getting of the method of final elements. A lot of computer programs is using this method. Because of the existence of many sorts of electric motors, one of the viewpoints is the principle of working, another one is the construction. I concentrate on problems of asynchronous motors. In this bachelors thesis I have done theoretical calculation and contact and noncontact method of measuring of warming of the asynchronous motor.
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