National Repository of Grey Literature 15 records found  previous11 - 15  jump to record: Search took 0.01 seconds. 
Experimental research of heterogeneous nuclei in superheated steam
Bartoš, Ondřej ; Kolovratník, M. ; Šmíd, Bohuslav ; Hrubý, Jan
A mobile steam expansion chamber has been developed to investigate experimentally homogeneous and heterogeneous nucleation processes in steam, both in the laboratory and at power plants using the steam withdrawn from the steam turbine. The purpose of the device is to provide new insight into the physics of nonequilibrium wet steam formation, which is one of the factors limiting the efficiency and reliability of steam turbines. The expanded steam or a mixture of steam with a non-condensable gas rapidly expands in the expansion chamber. Due to adiabatic cooling, the temperature drops below the dew point of the steam at a given pressure. When reaching a sufficiently high supersaturation, droplets are nucleated. By tuning the supersaturation in the so-called nucleation pulse, particles of various size ranges can be activated. This fact is used in the present study to measure the aerosol particles present in the air. Homogeneous nucleation was negligible in this case. The experiment demonstrates the functionality of the device, data acquisition system and data evaluation methods.
The influence of way and intensity of grassland exploitation on sward composition and crop yield
BARTOŠ, Ondrej
The aim of this work is to assess the influences of various methods of cultivating and making use of permanent grasslands in respect of their surface structure and productivity. At the same time we have to take into account the production and extra-production importance of permanent grasslands. That is affected by exploiting different pratotechnic methods (mowing, grazing, alternate ways of cultivation, absence of cultivation) which have an effect on the formation of vegetation structure of the grass growth. One of the consequent aspects is also fytocenologic and production characteristics of the grass growth. In the work there are also methods of assessment and classification of space types and the summary of the most widespread ones mentioned. The earning capability of various growth types and proper methods of their exploiting is also an important part of the work. Permanent grasslands are main component of fodder for livestock, and throught them we can make livestock farming more effective. For the best quality and profit of grasslands is necessary proper preparing a land, mainly by manuring and mulching. Well manured grasslands give higher crop yield than unmanured. Crop yield also dependson climatic conditions and soil qualities. Plant and grass biomass presents materials of identical origin, which can be used in various branches of agriculture and industry.Using appropriate pratotechnic procedures, corresponding with ecological and economical conditions, we can expect high-quality yield. Combination of mowing and grazing appears as the most convenient utilization of grasslands. Mulching is alternative and the cheapest way of farming on not used (by mowing or grazing) grasslands, because it prevents overgrowningUtilization of grasslands a grazings must be conected with enviromental protection and should be sustainable.
Nonequilibrium condensation processes in steam turbines in the light of new measurements of heterogeneous particles
Hrubý, Jan ; Kolovratník, M. ; Ždímal, Vladimír ; Bartoš, Ondřej ; Moravec, Pavel ; Jiříček, I.
In a steam turbine, droplets are formed either homogeneously or via heterogeneous nucleation on pre-existing heterogeneous particles. In a pioneering work, the present team developed a system to measure the number and size of heterogeneous particles down to diameter of 3 nm. This work reports on measurements at Power Plant Prunéřov II. For the first time, the data is at higher parameters (0.27 MPa, 250°C), and the diffusion battery was used to determine the size distribuition of the particles, showing count-mean diameter of about 13 nm.

National Repository of Grey Literature : 15 records found   previous11 - 15  jump to record:
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14 BARTOŠ, Ondrej
14 BARTOŠ, Ondřej
1 Bartoš, O.
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