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Počítačové modelování tepelného namáhání skleněné tabule při gravírování laserem
ZOUBEK, Tomáš
Computer modelling is often used to understand the nature or behaviour of physical phenomena. In this work, a three-dimensional computer model was created from a 25x30x4 mm (width x height x thickness) glass plate on which twenty dots with a radius of 371.54 ?m were burned using a laser engraving process. The distance between the dots was 1.25 mm. A computer simulation of the thermal stress of the laser engraving process was carried out on this model. The input parameters used were the laser travel time between points (0,5 s^(-1)), the duration of the laser discharge (0,5 s^(-1)), the laser power (30 W), the laser intensity and the laser density over a given area (given by equation 11), the heat flux coefficient of the glass sheet (5,7 Wm^(-2)K^(-1)) and the function controlling the firing of the laser beam at specific points and times (equations 5.4 and 5.5). The simulation was carried out for two variants that differed in the order of the fired points. For the first variant, the points were fired chronologically from left to right in rows, whereas for the second variant the points were fired in the order 1, 3, 5, 11, 13, 15, 7, 9, 17, 19, 2, 4, 12, 14, 6, 8, 10, 16 and 20. The second variant proved to be more optimal for the geometry and material studied. It resulted in less thermal stress, as lower temperatures were achieved with a defined laser beam, and at the same time there was a greater time delay between processes stressing the same locations.
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Design of a nitrogen Dewar vessel for electron microscopes
Brauner, Tomáš ; Voňka,, Jakub (referee) ; Urban, Pavel (advisor)
Observation of biological samples in electron microscopes in a state closest to the native state requires reaching cryogenic temperatures, most often with the use of liquid nitrogen (LN2). For this purpose a Dewar vessel with cooled copper thumb for cooling the sample holder and anticontamination shield inside the vacuum chamber of the scanning electron microscope (SEM) and focused ion beam (FIB) source was designed. Characteristics of the designed LN2 Dewar vessel were validated by measuring executed on the real functional sample. The reached temperature at the tip of the thumb under estimated heat load 2 W was 90,8 K. Corresponding refilling interval of LN2 is about 11 h. Experimentally measured data correlate with theoretically calculated characteristics. The designed Dewar vessel with a cooled thumb fulfills the required properties specified in the thesis assignment with a margin.
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Experimental equipment for testing of heat pipes efeciency
Vostřel, Vít ; Lošák, Petr (referee) ; Vlach, Radek (advisor)
This bachelor thesis deals with construction of a measuring apparatus for measuring efficiency of heat pipes. The thesis first discusses heat pipes and all components of the measuring apparatus in theoretical way and than it describes construction of the real model and all needed calculations. The apparatus contains a movable arm to which the measured heat pipes are attached. The Arm is able to move form 0° to 90°. The apparatus construction procedure is also described here. The whole apparatus is controlled from the computer using Excel, macros created in Excel and Data Streamer tool.
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Low temperature heat exchanger
Křivánek, František ; Toman, Filip (referee) ; Hejčík, Jiří (advisor)
The aim of this work is to design a low-temperature heat exchanger for a lyophilization device. The theoretical part of the work includes a basic description of lyophilization technology, a literature review of heat transfer at low temperatures with a focus on suitable construction materials and heat transfer fluids, and an overview of utilized heat exchanger designs. The practical part of the work deals with the actual design of the heat exchanger for indirect cooling in two variants, one of which utilizes a direct vaporization system of the heat transfer fluid, while the other focuses on purely liquid cooling.
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Feedwater heater design
Holčapek, Josef ; Tomáš,, Zdeněk (referee) ; Skála, Zdeněk (advisor)
This diploma thesis deals with the design of a feedwater heater. The aim of the work is to perform thermal, hydraulic and stress analysis. A preliminary technical documentation is also part of this work. The first part contains a summary of basic types of heat exchangers and processes of heat transfer. The main part is focused on thermal analysis to determine the main parameters of the heat exchanger. Next part is followed up by hydraulic analysis to determine the pressure drop of the heating water. After that is created design of heat exchanger with stress analysis of the proposed wall thicknesses of the shell, water chambers and tubesheet. Achieved results are summarized and evaluated at the end of the diploma thesis.
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Ventilation and air conditioning of a car cabine
Viščor, Petr ; Hejčík, Jiří (referee) ; Fišer, Jan (advisor)
In this work are described kinds and functions of air-conditioning systems which are used in cars. Further is described heat transfer between car cabin and ambient environment and issue of reduction of air-conditioning energy consumption. Last part of the work contains numerical simulation made by the THESEUS-FE 2.1 software package. This simulation was done on a model of the Toyota Prius car and was focused on effect of glazing on a temperature of the air inside the car cabin during hot summer days.
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Spent fuel storage casks thermal and physical properties investigation
Hlatký, Pavel ; Martinec, Jiří (referee) ; Šen, Hugo (advisor)
This work deals with questions of spent fuel storage casks thermal and physical properties investigation. Foundations of mathematics which are necessary for describing field of temperature are included. The work itself contains calculation methods which are split into two parts. The first one deals with simplified analytic solution and the second part solves the whole problem by the numerical computation.
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Airflow inside of a passenger car
Bělka, Miloslav ; Štětina, Josef (referee) ; Charvát, Pavel (advisor)
This bachelor thesis deals with hearting, air-conditioning, air distribution and airflow in a cabin of a passenger car. Ventilation of the cabin is needed for acceptable level of indoor air quality. The air supplied into the cabin is conditioned by heating or air conditioning system in order to achieve an appropriate level of thermal comfort of the passengers. Various arrangements of automotive heating and air-conditioning systems are described in the thesis. The thesis also includes the description and results of a set of measurements of air temperatures and air velocities inside of a passenger car cabin.
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