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Heat transfer by thermal radiation
Budovec, Michal ; Svoboda, Josef (referee) ; Foral, Štěpán (advisor)
This bachelor’s thesis deals with heat transfer, specifically with thermal radiation heat transfer by convection. The work is divided into theoretical part and calculations. The theoretical part describes basic thermomechanical notions and all kinds of heat transfer with the emphasis on heat transfer by radiation with convection. Heat conduction chapter describes the basic types of heat conduction. In chapter Heat transfer by convection are given criterion equations and examples for determining dimensionless numbers. Radiation heat transfer chapter focuses on heat transfer between two bodies and the radiation factor. With this equations and dimensionless numbers are quantifying variables in the calculation part. In the theoretical part is wrought calculation for a given case of heat transfer in the air and vacuum. The calculation is experimentally verified, from which is wrought protocol with the measurement and comparison with calculation and measurement in the air and vacuum.
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Electric arc heating
Kahoun, Karel ; Zelenka, Michal (referee) ; Šimek, David (advisor)
This bachelor's thesis deals with an arc heating in industrial applications. In this paper, there is described laboratory equipment for the generation of electric arc. Thesis also contains theoretical analysis of heat transfer from the arc to nearby object. The main part of the thesis is devoted to experimental measurement of heat transfer from the arc to the nearby object in relation to the electrical power and the surface finish of the object.
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Affecting the function of thermal release of circuit-breakers for different connection systems
Lednický, Ján ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Right function of securing electrical installations is one of the most important factors preventing people, animals and electrical devices themselves from being electrocuted. Circuit breakers with an overcurrent tripping unit work with bimetal. When the bimetal is warmed up enough, it causes disconnection of circuit. This prevents people and animals from being harmed. To make overcurrent tripping unit work the right way, we have to minimise unnecessary disfunction factors caused by thermal thaw and Joule´s heat. This thesis is aimed at gaining general knowledge of heat transmission and transition of electrical current into heat. There are going to be made temperature-rise curves using all available connection sets to evaluate the impact of each one on the tripping unit. Then, a temperature profile of the circuit breaker will be made using a simulation made using SoildWorks Flow Simulation program. Finally, critical places of the current path will be observed.
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Analysis of thermal field in electrical machines
Korta, Tomáš ; Makki, Zbyněk (referee) ; Deeb, Ramia (advisor)
The main objective of this work is familiarization with the design and functions of asynchronous motor and computing of the thermal analysis of this motor using program ANSYS Workbench. A 3D model of asynchronous motor is created using Autodesk Inventor program, then the thermal transient analysis of the motor is computed according to the finite element method. The motor temperature is measured using both contact and contactless methods in the case of no load of motor operation. A comparison of computed and measured results is performed. Finally different cooling methods of electrical machines are presented.
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Actual trends in heat exchangers production
Wajda, Jakub ; Mauder, Tomáš (referee) ; Jaroš, Michal (advisor)
The bachelor thesis is focused on the content of heat exchangers in the automotive industry, the latest developments of trends and the potential direction of development of this branch of industry. The first part deals with the heat transfer and distribution of heat exchangers according to various criteria. The second section describes the types of cooling auto parts, together with the applicable types of heat exchangers. Follow developments in this area, including economic data about products and anticipated market developments.
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Apparatus for measuring the thermal resistance of the gloves
Pelikán, Jakub ; Fišer, Jan (referee) ; Hejčík, Jiří (advisor)
This thesis deals with common problem health protection at work. Namely hand protection during the work in very cold environment. It’s an analysis of materials suitable for apparatus used for measuring the thermal resistance of the gloves. There was analysed a range of materials. Every single sample was tested for heat conductivity and afterwards was assessed the suitability of materials. Heat was generated by electricity. Ocured heat fields was assessed with thermocamera. After performed experiments of carbon fiber we haven’t reached any satisfying results which we could use for manufacturing of this device. On the other hand kapton film has given very interesting results which we would recommend eventually. Kapton film needs to be modify according to the method listed in the conlusion. This thesis gives us a clear overview and inspiration for additional research of this device. It finds it’s place in research facilities and companies manufacturing protective clothing.
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Designing of a hot water heater
Zdražil, Pavel ; Frömel, Zdeněk (referee) ; Baláš, Marek (advisor)
This thesis processes design of hot water heater. It was done thermal, hydraulic and basic strength calculations in the work and from their outcomes was set up a design of heat exchanger, which was afterwards modelled and drawn. In the beginning of the work is reader introduced to heat exchanger types and characteristics and also to its thermal processes. Then the work continues with thermal design of the heat exchanger, where the most important outcome is heat transfer surface with other geometric parameters, followed by hydraulic design, where pressure loss on water side was calculated. The calculations are finished up by basic strength design, calculating thickness of shell and tube walls. The thesis is ended with evaluation of computed design and description of its basic features.
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Study of thermal properties of phase change materials
Křivánková, Kateřina ; Krouská, Jitka (referee) ; Zmeškal, Oldřich (advisor)
The diploma thesis studies the thermal properties of materials, heat storage based on phase transformation. The aim of this study was to measure the thermal properties of materials using a heat accumulation phase transformation, particularly a commercial material available from the Phase Change Material Products Ltd. under the name PlusICE A118. Such materials are referred to as PCM (from Eng. Phase Change Material), and are used for instance as heat insulators in construction. First described the phase transformation of substances in general, then was defined accumulation of thermal energy. We have also described methods for determining the temperature (thermal analysis, stationary and transietní methods). Finally defined thermophysical parameters (thermal capacity, thermal conductivity, thermal conductivity), which were determined transient step method.
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New Elements of Heat Transfer Efficiency Improvement in Systems and Units
Turek, Vojtěch ; Klemeš,, Jiří (referee) ; Odstrčil, Miloslav (referee) ; Jegla, Zdeněk (advisor)
Zvýšení efektivity výměny tepla vede k poklesu spotřeby energie, což se následně projeví sníženými provozními náklady, poklesem produkce emisí a potažmo také snížením dopadu na životní prostředí. Běžné způsoby zefektivňování přenosu tepla jako např. přidání žeber či vestaveb do trubek ovšem nemusí být vždy vhodné nebo proveditelné -- zvláště při rekuperaci tepla z proudů s vysokou zanášivostí. Jelikož intenzita přestupu tepla závisí i na charakteru proudění, distribuci toku a zanášení, které lze všechny výrazně ovlivnit tvarem jednotlivých součástí distribučního systému, bylo sestaveno několik zjednodušených modelů pro rychlou a dostatečně přesnou predikci distribuce a také aplikace pro tvarovou optimalizaci distribučních systémů využívající právě tyto modely. Přesnost jednoho z modelů byla dále zvýšena pomocí dat získaných analýzou 282 distribučních systémů v softwaru ANSYS FLUENT. Vytvořené aplikace pak lze využít během návrhu zařízení na výměnu tepla ke zvýšení jejich výkonu a spolehlivosti.
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COMPUTING SOFTWARE AND METHODOLOGY DEVELOPMENT FOR REFRIGERATION MINICHANNEL CONDENSER EVALUATION
Pavlů, Jaroslav ; Masaryk, Michal (referee) ; Jaroš, Michal (referee) ; Pospíšil, Jiří (advisor)
Air cooled heat exchangers are used in many technology applications. Compactness, functionality and prize is decision maker for many future customers. Current development of compact heat exchangers is evident. Mostly used technology - expanded copper tube on aluminium fin is fluently changed by all aluminium heat exchangers with sophisticated heat exchange surface. Heating, Ventilating and Air-Conditioning with Refrigeration industry (HVAC-R) uses more and more extrude aluminium profiles as the main structure for all size heat exchangers. Similarly to Automotive industry HVAC-R uses minichannels as the basis of their products. It is not a new technology, it is technology proved through many years use in car industry. It is also true that current well known minichannel technology is not the last step. New designs and production lines are currently developed as well. All these new technologies have one unsolved thing together – how will be the new technologies easily computed through models. Current correlations which were used till now are obsolete, because of system miniaturization mainly. It is not easy to adapt old macro channel correlations on minichannel or microchannels where is not possible to diminish capillarity effects, different flow structures, etc. All these difficulties causes in model changes, software changes or iterative procedures upgrades. It is also evident that a lot of experimental exercises have to be done to examine heat exchanger behaviour ad characteristics. Because of precise computation of minichannel heat exchangers need or its geometry optimization is dissertation theme aimed to compare computation methodologies. PhD thesis is also aimed to check functionality of proposed computation system used simple similarity model. All proposed methods are compared to experimentally measured data and as the outcome of thesis are these data used to develop new computation basis.
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