244 research outputs found

    Condensing steam turbine

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    Cílem této diplomové práce je návrh kondenzační parní turbíny o zadaných parametrech. Nejprve je proveden návrh a výpočet tepelného schématu, následuje termodynamický výpočet průtočného kanálu turbíny a návrh vyrovnávacího pístu axiálních sil. V poslední části je posouzen vliv změny teploty chladicí vody na poslední stupně parní turbíny. Součástí práce je rovněž konstrukční výkres podélného řezu parní turbínou.The aim of the master’s thesis is to design a condensing steam turbine based on given inputs. Firstly, a design and computation of heat balance is made, followed by thermodynamic calculation of steam turbine channel and a design of compensatory piston of axial forces. Last part of the thesis consists of a review of a change of cooling water temperature in condensator on last turbine stages. The structural drawing of longitudinal section of turbine is included as well.

    Natural gas

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    Cílem této bakalářské práce je vypracovat rešerši na téma zemní plyn, především se zaměřením na Českou republiku. Nejprve bude pojednáno o zemním plynu obecně, jeho vlastnostech, světových zásobách, způsobech těžby a možnostech jeho využití. Hlavní část práce se pak zabývá zásobováním zemním plynem a jeho akumulací na území České republiky. Následuje vyjmenování a stručný popis možností náhrad zemního plynu a jeho současných zdrojů. V poslední části se pak nachází porovnání ekonomiky využití klasického a kondenzačního kotle při vytápění rodinného domu a doporučení typu kotle na základě modelového příkladu.The aim of the bachelor thesis is to collect facts about natural gas, focusing mainly on the situation in the Czech Republic. Firstly, the thesis discusses the natural gas in general - its properties, world resources, ways of production and usage. The main part of the thesis deals with supply and accumulation of natural gas in the Czech Republic. Secondly, enumeration and brief description of possibilities of natural gas substitution is presented. Finally, comparison of usage of classic non-condensing and condensing boiler for a family house heating is introduced. Recommendation of boiler type based on the model example is included as well.

    Poly[di-μ2-chlorido-dichlorido(μ3-di­methyl sulfoxide-κ3 O:O:S)(μ2-di­methyl sulfoxide-κ2 O:S)ruthenium(III)sodium]

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    The structure of the title compound, [NaRuCl4(C2H6OS)2]n, comprises centrosymmetric [RuCl2(DMSO)Na(DMSO)Cl2Ru] units (DMSO is dimethyl sulfoxide, C2H6OS), with two Ru atoms, each lying on a crystallographic centre of inversion, connected via Na atoms, DMSO and chloride ligands into a two-dimensional (110) array. Both RuIII atoms are octa­hedrally coordinated by four chloride ligands in the equatorial plane and by two DMSO mol­ecules in apical positions within a RuCl4S2 donor set. The Na atom is surrounded by three chloride anions and three O atoms derived from three DMSO mol­ecules, with the resulting Cl3O3 donor set defining an octa­hedron. The crystal structure is further stabilized by inter­atomic inter­actions of the types C⋯Cl [C—Cl = 3.284 (2) Å], C—H⋯Cl [C⋯Cl = 3.903 (3) Å] and C—H⋯O [C⋯O = 3.376 (3) Å]

    6-(2-Methoxy­benzyl­amino)purine

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    The title compound, C13H13N5O, consists of discrete mol­ecules connected by N—H⋯N hydrogen bonds to form infinite chains, with N⋯N separations of 3.0379 (15) and 2.8853 (15) Å. The benzene and purine ring systems make a dihedral angle of 77.58 (3)°. The crystal structure is further stabilized by intra­molecular N⋯O inter­actions [2.9541 (12) Å] and inter­molecular C—H⋯C and C⋯C contacts [3.304 (2), 3.368 (2), 3.667 (2), 3.618 (2) and 3.512 (2) Å] which arrange the mol­ecules into graphite-like layers. The inter­layer separations are 3.248 and 3.256 Å

    Di-μ-hydroxido-bis­[hemiaqua­(N,N,N′,N′-tetra­methyl­ethane-1,2-diamine)­copper(II)] bis­(tetra­fluoridoborate)

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    The title compound, [Cu2(OH)2(C6H16N2)2(H2O)](BF4)2, consists of dinuclear centrosymmetric [Cu2(OH)2(tmen)2(H2O)]2+ complex cations (tmen = N,N,N′,N′-tetra­methyl­ethane-1,2-diamine) and tetra­fluoridoborate anions. In the cation, the CuII atom shows a slightly distorted square-pyramidal coordination geometry provided by a pair of μ-OH− anions and by the N atoms of a chelate tmen ligand in the basal plane. The apical position is statistically occupied by the O atom of a half-occupancy water mol­ecule. The F atoms of the anion are disordered over three sets of sites with occupancies of 0.598 (9):0.269 (6):0.134 (8). The crystal packing is governed by ionic forces as well as by O—H⋯F hydrogen bonds

    PIV and LIF study of flow and thermal fields of twine plumes in water

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    Flow and thermal fields of a pair of plane plumes in water are investigated by means of PIV and LIF experiments. The plumes are generated from thermal line sources, which are made out of electrically heated cylinders with a diameter of D = 1.21 mm. A cylinder-to-cylinder distance was 17.9 D. Either continuous or pulsating heating were used with the same heating input power. Because the cylinder-to-cylinder distance is moderately small, deflections of plumes from a vertical direction occur and the plumes are inclined together. This behavior is caused by a confined entrainment from a space between the both plumes. For a continuous heating, low frequency oscillations were identified and the natural frequency was evaluated as 0.5 Hz. Based on this finding, pulsating heating was used at the subharmonic frequency of 0.25 Hz. The maximum time-mean velocity magnitude at the continuous and pulsating heating were commensurable, approximately 0.007 m/s. On the other hand, pulsating heating achieves by 36 % higher velocity peaks. A very strong velocity oscillations were generated by pulsating heating at the distance approximately 8.3 D above the cylinders, where the velocity maxima oscillate along the time-mean value of 0.0057 m/s from −30% to +70 %. Temperature fields reasonably agree with this findings, despite a relatively fast equalization of the temperature field was concluded. The results demonstrate enhancement effects of pulsations in flow/thermal fields

    (μ-5-Carboxy­benzene-1,3-dicarboxyl­ato-κ2 O 1:O 3)bis­[bis­(2,2′-bipyridine-κ2 N,N′)copper(II)] 5-carboxy­benzene-1,3-dicarboxyl­ate 2,2′-bipyridine solvate trideca­hydrate

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    The asymmetric unit of the title complex, [Cu2(C9H4O6)(C10H8N2)4](C9H4O6)·C10H8N2·13H2O, comprises two formula units. The two CuII centres are bridged by a 5-carb­oxy­benzene-1,3-dicarboxyl­ate (Hbtc) ligand. Each of the metal centres is bonded to four N atoms of two bidentate 2,2′-bipyridine ligands (bpy) and one O atom of the Hbtc ligand in a highly distorted square-pyramidal geometry. The secondary structure is stabilized by a variety of O—H⋯O hydrogen bonds and π–π stacking inter­actions connecting the complex cations, Hbtc anions, bpy and water mol­ecules of crystallization. Three water molecules are disordered over two positions, with site occupancy factors of ca 0.8 and 0.2

    Bis(4,7-dichloro-1,10-phenanthroline-κ2 N,N′)bis­(dicyanamido-κN)copper(II)

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    In the title compound, [Cu(C2N3)2(C12H6Cl2N2)2], the CuII atom is coordinated by two chelating 4,7-dichloro-1,10-phenanthroline (4,7-Cl-phen) ligands and two dicyanamide (dca) ligands in a cis arrangement, forming a distorted octa­hedral geometry. The equatorial plane is occupied by three N atoms from two 4,7-Cl-phen ligands and one N atom from a dca ligand at shorter Cu—N distances. Due to the Jahn–Teller effect, the axial positions are occupied by a 4,7-Cl-phen N atom and a dca N atom at longer Cu—N distances. The dca ligands are nearly planar, with a maximum deviations of 0.006 (1) Å. The crystal structure is stabilized by weak C—H⋯N hydrogen bonds, with cyanide N atoms as acceptors, and π–π inter­actions between adjacent phenyl rings [centroid–centroid distance = 3.725 (3) Å]

    The impact of the solvent dielectric constant on A←NH3 dative bond depends on the nature of the Lewis electron-pair systems

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    The present work aims to determine to what extent the value of the dielectric constant of the solvent can influence the dative bond in Lewis electron pair bonding systems. For this purpose, two different systems, namely H3B <- NH3 and {Zn <-(NH3)}(2+), were studied in selected solvents with significantly different dielectric constants. Based on the results from state-of-the-art computational methods using DFT, constrained DFT, energy decomposition analyses, solvent accessible surface area, and charge transfer calculations, we found that the stability of the neutral H3B <- NH3 system increases with increasing solvent polarity. In contrast, the opposite trend is observed for the positively charged {Zn <-(NH3)}(2+). The observed changes are attributed to different charge redistributions in neutral and charged complexes, which are reflected by a different response to the solvent and are quantified by changes in solvation energies.Web of Science293

    Aqua­(4-methyl­quinoline-κN)[N-(2-oxidobenzyl­idene)glycinato-κ3 O,N,O′]copper(II) hemihydrate

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    The title complex, [Cu(C9H7NO3)(C10H9N)(H2O)]·0.5H2O, crystallizes with two independent formula units in the asymmetric unit; the solvent mol­ecule is located on a twofold axis of symmetry. The CuII atom is coordinated by one tridentate N-salicylideneglycinate Schiff base ligand, one 4-methyl­quinoline ligand and one water mol­ecule, leading to a slightly distorted square-pyramidal N2O3 geometry. In the crystal structure, the mol­ecules are linked by O—H⋯O hydrogen bonds into linear chains in the [100] direction. The structure is further stabilized by inter­molecular C—H⋯O inter­actions and C⋯C contacts with C⋯C = 3.3058 (2), 3.3636 (2) and 3.3946 (2) Å
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