Using Adiabatic Cooling to Reduce Energy Consumption

Práce se zabývá využitím nepřímého vypařovacího chlazení v zařízeních pro zpětné získávání tepla. Nepřímé vypařovací chlazení je identifikováno jako výhodná metoda nízkoenergetického chlazení větracího vzduchu vypařováním vody, bez přímého navlhčení větracího vzduchu. Výhodami tohoto způsobu chlazení jsou minimální energetický vklad i fakt, že touto metodou je možné chladit budovy i v době největších tepelných zátěží, které jsou pro nízkoenergetické chlazení často kritické. Práce si klade za cíl připravit základnu poznatků pro snadný transfer této technologie do nejběžnější technické praxe a na trh vzduchotechnických jednotek. V první části práce je celá myšlenka nepřímého vypařovacího chlazení popsána. Je uveden kontext problematiky a vytyčen současný stav poznání. Z rešerše literatury vyplývá, že na světě chybí jednoduchý popis děje ve skrápěném tepelném výměníku vzduch/vzduch, který nepřímé vypařovací chlazení zajišťuje. Tento děj je dosud popisován složitými modely a diferenciálními rovnicemi, chybí ale rychlý inženýrský nástroj pro výpočet parametrů vlhkého vzduchu za takovým výměníkem, na základě měřitelných nebo lehce dosažitelných vstupních údajů. V praktické části pak disertační práce míří k vytvoření takového nástroje. Je popsána cesta od získání experimentálních dat, přes složitý model vytvořený s pomocí teorie podobnosti, metody konečných objemů a mechaniky tekutin, k jednoduchému modelu, který je ověřen proti všem dostupným validačním základnám. Jednoduchý model je omezen na křížoproudé výměníky se svislými deskami, souproudem vody a sekundárního vzduchu a gravitačním pohybem vodního filmu po teplosměnné ploše. V těchto okrajových podmínkách model vykazuje velmi dobrou shodu jak s vlastními experimentálními daty, tak s experimenty a modely jiných autorů. Vyvinutý jednoduchý model je představen jako hledaný inženýrský nástroj, který z jednoduchých vstupních dat přímým výpočtem stanoví teplotu větracího vzduchu za zařízením nepřímého vypařovacího chlazení. V závěrečné části práce jsou shrnuty technické překážky v implementaci nepřímého vypařovacího chlazení do běžné vzduchotechniky a několik doporučení pro konstrukci těchto zařízení. Jsou tak komunikovány zkušenosti získané dlouhodobým experimentem. Potenciál nepřímého vypařovacího chlazení je uveden do kontextu klimatických dat a je i vyjádřena cena získaného chladu započtením spotřeby vody. Nepřímé vypařovací chlazení je shledáno jako výhodné po energetické, ekologické i ekonomické stránce.The work deals with the use of indirect evaporative cooling in heat recovery devices. Indirect evaporative cooling is identified as an advantageous method of low-energy cooling of the ventilation air by water evaporation, without direct humidifying of the ventilation air. The advantages of this method of cooling are the minimum energy input and the fact that this method can be used to cool buildings even during daytime of high heat loads, which are often critical for low energy cooling. The aim of the thesis is to prepare the basis of knowledge for easy transfer of this technology to the most common technical practice and to the market of air handling units. In the first part of the thesis, the idea of indirect evaporative cooling is described, including the paradox of the widespread name "Adiabatic Cooling", which in conjunction with this technology is not entirely correct. The context of the issue is described and the current state of knowledge is outlined. The literature research suggests that there is no simple description in the world of the process in a sprinkled air / air heat exchanger that provides indirect evaporation cooling. This process is still described by complex models and differential equations, but there is no quick engineering tool for calculating the parameters of moist air in a heat exchanger, based on measurable or easily obtainable input data. In the practical part, the thesis aims to create such an instrument. The way from obtaining experimental data, through a complex model created using the theory of similarity, finite volume method and fluid mechanics, is described to a simple model that is validated against all available validation bases. The simple model is limited to cross-flow heat exchangers with vertical plates, co-current of water and secondary air flow, and gravitational movement of water film over the heat transfer surface. In these boundary conditions, the model shows very good agreement with both experimental data and experiments and models of other authors. Developed simple model is presented as the searched engineering tool that provides a simple computation of supply air temperature after indirect evaporative cooling process, using only basic and obtainable input data. In the final part of the thesis there are summarized technical obstacles in the implementation of indirect evaporative cooling to common ventilation and several recommendations for the construction of these devices. Thus, the experience gained through a long-term experiment is communicated. The potential of indirect evaporative cooling is brought into the context of climatic data and the price of the obtained coolness is also expressed by counting the water consumption. Indirect evaporative cooling is found to be beneficial in energy, environmental and economic terms

Proučavanje Au/KCl sustava pomoću RHEED-A radi ocjene ovisnosti profila difrakcionih točaka o veličini čestica

The reflection high energy electron diffraction (RHEED) method has been used for the investigation of Au cluster growth on KCl substrate. The formation of three-dimensional particles was observed. The morphological parameters of the particles (i.e. diameter and density) were estimated ex-situ by transmission electron microscopy (TEM) and the results were compared with the RHEED spot profiles. Au particles were chosen, because they did not change their parameters by the reconstruction caused by oxidation during the preparation for TEM measurements.Primijenjena je refleksijska difrakcija elektrona više energije (RHEED) u istraživanju rasta Au nakupina na KCl podlozi. Opaženo je oblikovanje trodimenzijskih zrnaca. Oblici zrnaca naknadno su određeni transmisijskom elektronskom mikroskopijom i rezultati su uspoređeni s analizama RHEED profila točaka

BaTiO3 FILMS DEPOSITED ONTO TiNb AND Ti SUBSTRATES - AMOUNT AND STABILITY OF BARIUM

BaTiO3 films deposited onto TiNb and Ti substrates using hydrothermal synthesis method were studied in the presented work. These films are supposed to improve properties of bone implants due to their ferroelectric behaviour, because ferroelectrics induce improved bone formation. A great question is the chemical stability of the used material. It can be crucial for its biocompatibility and possible in vivo application. We studied chemical composition of prepared samples, especially concentration of Ba and Ti and trends of these concentrations stimulated by a solution saline action. The Ba and Ti concentrations were determined by XPS under ultra - high vacuum condition. The BaTiO3 films were investigated as received after the preparation procedure as well as after a long - time treatment in solution saline. Every sample was introduced to the solution saline at first for 1 and later for 3 weeks. Ti concentration almost does not change during our experiments while a meaningful Ba decrease is observed. Nevertheless, barium release seems to slow down with respect to the time of solution saline action. Stability of barium titanate films in a period of several months and an absolute amount of the released barium will be a subject of the next research

BaTiO3 FILMS DEPOSITED ONTO TiNb AND Ti SUBSTRATES - AMOUNT AND STABILITY OF BARIUM

BaTiO3 films deposited onto TiNb and Ti substrates using hydrothermal synthesis method were studied in the presented work. These films are supposed to improve properties of bone implants due to their ferroelectric behaviour, because ferroelectrics induce improved bone formation. A great question is the chemical stability of the used material. It can be crucial for its biocompatibility and possible in vivo application. We studied chemical composition of prepared samples, especially concentration of Ba and Ti and trends of these concentrations stimulated by a solution saline action. The Ba and Ti concentrations were determined by XPS under ultra - high vacuum condition. The BaTiO3 films were investigated as received after the preparation procedure as well as after a long - time treatment in solution saline. Every sample was introduced to the solution saline at first for 1 and later for 3 weeks. Ti concentration almost does not change during our experiments while a meaningful Ba decrease is observed. Nevertheless, barium release seems to slow down with respect to the time of solution saline action. Stability of barium titanate films in a period of several months and an absolute amount of the released barium will be a subject of the next research

Distribution of deep-water corals, sponges, and demersal fisheries landings in Southern California, USA: implications for conservation priorities

Deep-sea corals in Southern California are diverse and abundant but subject to multiple stressors, including bottom-contact fisheries using mobile and fixed gear. There is a need for more information on the distribution of these taxa in relation to the distribution of demersal fishing effort, and the distribution of marine protected areas, in order to improve spatial planning. There are many marine managed areas in Southern California, including essential fish habitat (EFH) areas, conservation areas, and a national marine sanctuary, but specific areas of overlap between bottom fishing and benthic epifauna are poorly known. Groundfish surveys were conducted by the National Marine Fisheries Service using a remotely operated vehicle throughout Southern California between 2003 and 2011 to document abundance and distribution of deep-water rockfish and flatfish to a depth of 500 m. Corals and sponges were also common in these images, providing an opportunity to examine these communities. Analyses of 34,792 still images revealed abundance and diversity of coral and sponge taxa, as well as frequency of fishing debris. The occurrence data were overlaid in a geographic information system with landings data for deep-water (>50 m) demersal fisheries to identify areas of spatial overlap. Corals or sponges were observed in 23% of images. A total of 15 coral genera and six sponge morphotypes were identified. A total of 70 species codes were targeted by deep-water demersal fisheries operating below 50 m for years 2007–2011. A novel priority-setting algorithm was developed to identify areas of high richness, abundance, and fishing intensity (RAFi). Several highly-ranked areas were already protected as EFH (Footprint, Piggy Bank). Other highly-ranked sites (West Catalina Island, San Clemente Island, 9-Mile Bank, Santa Rosa Flats) were encompassed by transient gear restrictions, such as Rockfish conservation areas, but are now recommended for permanent protection by the Pacific Fishery Management Council

Final surface modification for better wear resistance of ceramic coating on cast AlSi10Mg alloy

Using the design of experiment (DOE) method and the micro-arc oxidation (MAO) technique, ceramic layers on AlSi10Mg alloy were systematically prepared to design optimal process conditions for achieving the best tribological properties of the ceramic layers. The lowest concentrations of the applied 6 g/l NaOH and 12 g/l Na2SiO3 resulted in the preparation of uniform MAO layers with the lowest rated parameters Ra, Rz and thickness achieved under micro-arc discharge conditions at 500 V and 60 min. With the increasing thickness of the coatings, there was an increase of Si in the MAO coating. Full factorial DOE was used to optimize the tribological properties in a polyalphaolefin (PAO) environment at 80 degrees C. The most significant influence for the preparation of abrasion-resistant layers for the investigated factors was identified on the AlSi10Mg alloy by the NaOH content in the electrolyte. The friction coefficients of MAO coatings reached an average value of 0.15. Aero-lap polishing technology was applied for increased wear resistance requirements to eliminate the deficiencies of MAO coat-ings, leading to decrease wear track by almost double compared to polished silumin. Removal of the outer MAO layer by polishing led to a reduction in the high corrosion resistance of the MAO coating, demonstrating the influence of the outer layer not only on the tribological properties but also on the corrosion resistance of MAO coatings.Web of Science4824374473743

Hybrid coatings for orthopaedic implants formed by physical vapour deposition and microarc oxidation

This study is focused on the preparation of new hybrid layers intended for surface modification of Ti-6Al-4V alloys for potential orthopaedic and dental applications. Combination of the technology of physical vapour deposition (PVD) and subsequent micro-arc oxidation (MAO) was utilized for the deposition of Ti and ZrTi to form hybrid oxide layers. The oxide layers were prepared using an alkaline electrolyte with glycerol as an additive under micro-arc discharge conditions with different Si content on their surfaces. The hybrid ZrTi coatings with a Zr/Si structure achieved the best tribological properties described by a low friction coefficient of 0.3 and high abrasion resistance. There was also an increase in corrosion potential and polarization resistance of hybrid ZrTi coatings. Although the proliferation of human bone marrow mesenchymal stem cells was slower on these hydrophilic Ti and ZrTi coatings than both on uncoated Ti-6Al-4V and the reference tissue culture polystyrene dishes, both types of hybrid coating promoted greater osteogenic differentiation of these cells, indicated by approx. twice as high activity of alkaline phosphatase. The hybrid oxide layers newly developed in this study - especially the layers with Zr - are therefore promising for coating metallic bone implants.Web of Science219art. no. 11081

Ablation of single-crystalline cesium iodide by extreme ultraviolet capillary-discharge laser

Extreme ultraviolet (XUV) capillary-discharge lasers (CDLs) are a suitable source for the efficient, clean ablation of ionic crystals, which are obviously difficult to ablate with conventional, long-wavelength lasers. In the present study, a single crystal of cesium iodide (CsI) was irradiated by multiple, focused 1.5-ns pulses of 46.9-nm radiation delivered from a compact XUV-CDL device operated at either 2-Hz or 3-Hz repetition rates. The ablation rates were determined from the depth of the craters produced by the accumulation of laser pulses. Langmuir probes were used to diagnose the plasma plume produced by the focused XUV-CDL beam. Both the electron density and electron temperature were sufficiently high to confirm that ablation was the key process in the observed CsI removal. Moreover, a CsI thin film on MgO substrate was prepared by XUV pulsed laser deposition; a fraction of the film was detected by X-ray photoelectron spectroscopy.Web of Science65421020