THE CONDENSATION OF WATER VAPOUR IN A MIXTURE CONTAINING A HIGH CONCENTRATION OF NON-CONDENSABLE GAS IN A VERTICAL TUBE

This paper deals with the condensation of water vapour possessing a content of noncondensable gas in vertical tubes. The condensation of pure steam on a vertical surface is introduced by the Nusselt condensation model. However, the condensation of water vapour in a mixture with non-condensable gas differs from pure vapour condensation and is a much more complex process. The differences for the condensation of water vapour in a mixture containing a high concentration were theoretically analysed and evaluated. In order to investigate these effects, an experimental stand was built. Experiments were carried out in regards to the case of pure steam condensation and the condensation of water vapour with a non-condensable gas mixture to evaluate the influence of the variable non-condensable gas content during the process. A non-condensable gas in a mixture with steam decreases the intensity of the condensation and the condensation heat transfer coefficient. A gradual reduction of the volume and partial pressure of steam in the mixture causes a decrease in the condensation temperature of steam, and the temperature difference between steam and cooling water. The increasing non-condensable gas concentration restrains the transportation of steam towards the tube wall and this has a significant effect on the decrease in the condensation rate

Utilisation of Solar Energy in a Family House

V Bakalářská práci se zabývám využitím sluneční energie v rodinném domě. Kdy se nejprve v teoretické části věnuji možnostem využití sluneční energie pro přípravu teplé vody na území České republiky. V praktické části pak provádím návrh a výpočet tepelné solární soustavy na přípravu teplé vody pro konkrétní rodinný dům obývaný 2 osobami. V závěru práce následně stanovuji měsíční a roční zisky soustavy, a dále navrženou tepelnou solární soustavu analyzuji z ekonomického a environmentálního hlediska.In the bachelor thesis I deal with utilisation of solar energy in a family house. In the first (theoretical) part I write about thermic solar panels and its possibilities of use for water heating in family houses in the Czech Republic. Then in the practical part I make calculation and design of the solar system for specific family house inhabited by 2 people. In the final part I analyze designed solar system from an economic and environmental point of view.361 - Katedra energetikyvýborn

Preparation of some application formula of antimicrobial substances

Táto práca sa zameriava na štúdium antimikrobiálneho pôsobenia extraktov z vybraných bylín, následnú enkapsuláciu týchto extraktov a enkapsuláciu lyzozýmu. V teoretickej časti bola spracovaná literárna rešerš zaoberajúca sa problematikou prírodných antimikrobiálnych látok, na základe ktorej boli vybraté testované bylinky. Extrakty pripravené z paliny pravej (Artemisia absinthium), materinej dúšky (Thymus serpyllum), koreňa echinacey purpurovej (Echinacea purpurea), sladovky hladkoplodej (sladkého drievka) (Glycyrrhiza glabra), nechtíka lekárskeho (Calendula officinalis) a plodov rakytníka rašetliakového (Hippophae rhamnoides) boli najskôr charakterizované na obsah polyfenolov, flavonoidov a celkovú antioxidačnú aktivitu. Ďalej boli tieto extrakty enkapsulované do lipozómov a rovnako bol enkapsulovaný aj lyzozým. Následne bola sledovaná stabilita týchto častíc vo vodnom prostredí. Antimikrobiálna aktivita týchto látok v enkapsulovanom aj neenkapsulovanom stave bola testovaná na bakteriálnych kmeňoch Escherichia coli, Serratia marcescens, Bacillus subtilis a Micrococcus luteus, voči ktorým, väčšina vybraných extraktov vykazovala antimikrobiálnu aktivitu.The main aim of this study is to determine antimicrobial activity of herbal extracts and also encapsulate these extracts and lysozyme to liposomes. The extracts were prepared from above ground part of wormwood (Artemisia absinthium), aerial part of breckland thyme (Thymus serpyllum), the root of purple coneflower (Echinacea purpurea), liquorice (Glycyrrhiza glabra), corolla of pot marigold (Calendula officinalis) and berries of sea buckthorn (Hippophae rhamnoides). In all extracts antioxidant activity and the amount of total polyphenols and flavonoids was determined. All of these extracts and also lysozyme were used for encapsulation to liposomes. Prepared liposomes were then tested for their stability. Further, encapsulated as well as free extracts were tested for their antimicrobial activity on Escherichia coli, Serratia marcescens, Micrococcus luteus and Bacillus subtilis. Extract from Echinacea purpurea showed the highest antimicrobial activity.

Energy Management of the Logistics Center

Diplomová práce se zabývá snížením spotřeby energie a zvýšením energetické nezávislosti logistické haly. Teoretická část je rozdělena do dvou částí, kdy se v první části řeší problematika fotovoltaiky a fotovoltaických systémů, v druhé části se řeší problematika kogenerace a kogeneračních jednotek. Praktická část diplomové práce je opět rozdělena do dvou částí. V první praktické části je proveden technický návrh a výpočet fotovoltaické elektrárny, která je následně zhodnocena z ekonomického a enviromentálního hlediska pomocí vztahů uvedených ve vyhlášce o energetickém auditu. V druhé praktické části je proveden opět technický návrh a výpočet kogenerační jednotky se spalovacím motorem, navržená jednotka je dále posouzena z ekonomického a enviromentálního hlediska.The thesis deals with the reduction of energy consumption and the increase of energy independence of the logistics hall. The theoretical part is divided into two parts, the first part deals with photovoltaics and photovoltaic systems, the second part deals with cogeneration and CHP units. The practical part of the thesis is again divided into two parts. In the first practical part, the technical design and calculation of a photovoltaic power plant is carried out, which is then evaluated from an economic and environmental point of view using the relationships listed in the decree on energy audit. In the second practical part, the technical design and calculation of a CHP unit with an internal combustion engine is again carried out, and the proposed unit is further assessed from an economic and environmental point of view.361 - Katedra energetikyvýborn

Theoretical and experimental study of water vapour condensation with high content of non-condensable gas in a vertical tube

This article deals with the possibility of separating water vapour from flue gases after oxyfuel combustion using condensation processes. Those processes can generally be described as condensation of water vapour in the presence of non-condensable gases. Hence, the effect of noncondensable gas (NCG) on the condensation process has been theoretically and experimentally analysed in this study. The theoretical model was developed on the basis of the heat and mass transfer analogy with respect to the effect of the NCG, the flow mode of the condensate film, the shear stress of the flowing mixture, subcooling and superheating. Subsequently, an experimental analysis was carried out on a 1.5m long vertical pipe with an inner diameter of 23.7mm. The mixture of vapour and air flowed inside the inner tube with an air mass fraction ranging from 23% to 62%. The overall heat transfer coefficients (HTC) from the theoretical model and experimental measurement are significantly lower than the HTC obtained according to the Nusselt theory for the condensation of pure water vapour. The overall HTC decreases along the tube length as the gas concentration increases, which corresponds to a decrease in the local condensation rate. The highest values of the HTC are observed in the condenser inlet, although a strong decrease in HTC is also observed here. Meanwhile, there is a possibility for an HTC enhancement through turbulence increase of the condensing mixture in the condenser outlet. Results also showed that the heat resistance of the mixture is several times higher than the heat resistance of the condensate film. The developed theoretical model based on heat and mass transfer analogy is in good agreement with experimental results with the standard deviation within +25% and −5%. The model is more accurate for lower NCG concentrations

Persistence of structural distortion and bulk band Rashba splitting in SnTe above its ferroelectric critical temperature

The ferroelectric semiconductor $\alpha$-SnTe has been regarded as a topological crystalline insulator and the dispersion of its surface states has been intensively measured with angle-resolved photoemission spectroscopy (ARPES) over the last decade. However, much less attention has been given to the impact of the ferroelectric transition on its electronic structure, and in particular on its bulk states. Here, we investigate the low-energy electronic structure of $\alpha$-SnTe with ARPES and follow the evolution of the bulk-state Rashba splitting as a function of temperature, across its ferroelectric critical temperature of about $T_c\sim 110$ K. Unexpectedly, we observe a persistent band splitting up to room temperature, which is consistent with an order-disorder contribution to the phase transition that requires the presence of fluctuating local dipoles above $T_c$. We conclude that no topological surface state can occur at the (111) surface of SnTe, at odds with recent literature.Comment: 26 pages, 8 figure

Field-induced ultrafast modulation of Rashba coupling at room temperature in ferroelectric α\alpha-GeTe(111)

Rashba materials have appeared as an ideal playground for spin-to-charge conversion in prototype spintronics devices. Among them, $\alpha$-GeTe(111) is a non-centrosymmetric ferroelectric (FE) semiconductor for which a strong spin-orbit interaction gives rise to giant Rashba coupling. Its room temperature ferroelectricity was recently demonstrated as a route towards a new type of highly energy-efficient non-volatile memory device based on switchable polarization. Currently based on the application of an electric field, the writing and reading processes could be outperformed by the use of femtosecond (fs) light pulses requiring exploration of the possible control of ferroelectricity on this timescale. Here, we probe the room temperature transient dynamics of the electronic band structure of $\alpha$-GeTe(111) using time and angle-resolved photoemission spectroscopy (tr-ARPES). Our experiments reveal an ultrafast modulation of the Rashba coupling mediated on the fs timescale by a surface photovoltage (SPV), namely an increase corresponding to a 13 % enhancement of the lattice distortion. This opens the route for the control of the FE polarization in $\alpha$-GeTe(111) and FE semiconducting materials in quantum heterostructures