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Temperature Profile in Reflow Soldering and Influence of Different PCBś and ComponentsThermal Capacities
Procházka, Martin ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This thesis mainly deals with the prediction of temperature on the components and the PCB during reflow soldering. The theoretical part describes the particular solder reflow process, types of heat transfer and temperature profiles. The practical part is divided into forecasting temperatures if the conveyor is stopped and the temperature predictions when the conveyor is in motion. In both parts of the measured temperature is compared with the predicted temperatures, which show the success rate of prediction. The last part of this work is part of the simulation, which helps in proper understanding of the issues discussed.
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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.
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Thermoproperties of foundry moulds in dependence on different used foundry sands
Šuráň, Jiří ; Rusín, Karel (referee) ; Cupák, Petr (advisor)
The project elaborated in frame of engineering studies is submitting the study of thermal properties of holding mixtures using different types of sand. Were tested a total of 5 sands: zirkon, ŠH22, chromite, olivine and dunite. Molding compounds were tested for thermal capacity, thermal conductivity and heat accumulation. The highest heat capacity was achieved in dunite sand. The largest heat accumulation had mixture with chromite sand and the best thermal conductivity was found in a mixture with olivine sand.
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Identification of Thermal Conductivity and Thermal Capacity of Building Materials by the "Hot Wire Method"
Průša, David ; Čermák,, Jan (referee) ; Šťastník, Stanislav (advisor)
This aim of task deals with study of heat dissipation mechanisms and the description of physical phenomena, which is accompanied by non-stationary measurement of thermal characteristics by the method "hot-wire method". In particular, we observe the coefficient of thermal conductivity and its dependence on various variables such as the temperature of the measured sample, its moisture state, the volume of the sample and its porosity. The above mentioned findings are used for the invention of the measuring device of a nonstationary gauge, which is based on regular heating and is dedicated to measuring the thermal conductivity coefficient and the heat capacity by the "hot-wire method" method. In the last part of the thesis is verified functionality of the proposed measuring device, the suitability of the created algorithm for the processing of the measured data and the evaluation of the results was verified. The reproducibility of the measurements was verified and the measured results were compared with the measurement methods, which are commonly used. the influence of humidity on the coefficient of thermal conductivity.
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Study of applicability of suitable materials for long-term storage of heat energy
Bukvová, Veronika ; Šot, František (referee) ; Šťastník, Stanislav (advisor)
This bachelor thesis deals with appropriate ways of storing thermal energy and selection of materials for a high capacity storage unit. The thesis describes technologies currently used for long-term storage of thermal energy, structural arrangement of the thermal unit, physical properties of the materials usable for construction of high-temperature storage units and the utilization of these materials. The thesis also describes the measuring procedure of the material characteristics and the method of evaluation.
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Model for the Cable Thermal Characteristic Calculation
Starý, Zdeněk ; Drápela, Jiří (referee) ; Orságová, Jaroslava (advisor)
The result of this assignment is the Model for the Cable Thermal Characteristic Calculation. Firstly, there is a prepared overview that is focused on the essential ideas of cable technology. The following part describes the simple possibilities of passaging the heat. Secondly,the physical essence of warming cables as well as the possibility to discover the methods how to calculate the warming cables are also mentioned in this task.There is an opportunity to find the methods for calculating the warming cables as well. The model was verificationed in the conclusion of my assignment. The measurement was done and the empirical results were compared with the results that were achieved by modeling.
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Creation of laboratory tasks for Selected topics from renewable energy sources and energy storage
Vaněček, Lukáš ; Vaněk, Jiří (referee) ; Bača, Petr (advisor)
This master‘s thesis contains a comprehensive laboratory task about saving a heat energy with a use of changing a state of matter. The thesis is written for the object Chosen passages of renewable resources and saving a heat energy. Part one presents a theoretical part of the topic, terminology and relations needed to make this laboratory work. It also contains a created procedure of partial tasks necessary to take laboratory measurements. The second part of the thesis is about measuring and evaluation of acquired values according to procedure described in the theoretical part of the thesis. Different variations considered during the creation of measuring procedure are also named here. The final part of the thesis describes a laboratory equipment necessary to complete the task and an example of filled protocol is attached.
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Calculation of temperature field of the busbar bridge
Měrka, Ivan ; Maxa, Jiří (referee) ; Vyroubal, Petr (advisor)
This term project’s aim is to theoreticaly analyze thermal phenomena and losses in electrical power devices, describe the design and application of UniGear ZS1 type switchgear, put together a computer simulation model for thermal calculations of current and optimized solution and finally to discuss obtained results and compare them with experimentally acquired values. The main objective of this project is to determine, whether simulation is a viable and reliable enough method, that it could replace the costly real life physical testing. Modelling of the progress of thermal processes in different parts of the examined busbar will be done in computer aided design program Solidworks and its simulation plugin Flow Simulation.
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Thermal characteristics of power conductors
Měrka, Ivan ; Novotný, Jan (referee) ; Orságová, Jaroslava (advisor)
This bachelor’s thesis aims to theoreticaly analyze thermal phenomena in power conductors and construct a simulation of thermal characteristics of conductor under load. First, power conductors and their classification is discussed. Following are elementary information in thermomechanics and ways of heat transfer. Next chapter talks about different ways of cable laying with respect to their steady temperatures and the design of conductor’s cross section. Further chapter focus on unsteady state of the heating conductor, analysis of Van Wormer’s method for acquisition of thermal characteristics and in this method the model for parameterized conductors is based. In conclusion the simulated results are verified and compared to the results of practical laboratory measurement.
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