Browsing by Author "Vestfálová Magda"

Now showing 1 - 9 of 9
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    Description of saturation curves and boiling process of dry air
    (EDP Sciences, 2018-01-01) Vestfálová Magda; Petříková Markéta; Šimko Martin
    Air is a mixture of gases forming the gas wrap of Earth. It is formed by dry air, moisture and other pollutants. Dry air is a substance whose thermodynamic properties in gaseous state, as well as the thermodynamic properties of its main constituents in gaseous state, are generally known and described in detail in the literature. The liquid air is a bluish liquid and is industrially used to produce oxygen, nitrogen, argon and helium by distillation. The transition between the gaseous and liquid state (the condensation process, resp. boiling process), is usually displayed in the basic thermodynamic diagrams using the saturation curves. The saturation curves of all pure substances are of a similar shape. However, since the dry air is a mixture, the shapes of its saturation curves are modified relative to the shapes corresponding to the pure substances. This paper deals with the description of the dry air saturation curves as a mixture, i.e. with a description of the process of phase change of dry air (boiling process). The dry air saturation curves are constructed in the basic thermodynamic charts based on the values obtained from the literature. On the basis of diagrams, data appearing in various publications are interpreted and put into context with boiling process of dry air.
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    Determination of the applicability limits of the ideal gas model for the calculation of moist air properties
    (EDP Sciences, 2018-01-01) Vestfálová Magda; Šafařík Pavel
    The submitted paper deals with the finding of such moist air states in which the components of moist air and hence the humid air itself can be described by the ideal gas model while maintaining a predefined accuracy. Both components of moist air (dry air and water vapor) can be described by a model of ideal gas at sufficiently low pressures and sufficiently high temperatures. In the paper, we are looking for such combinations of pressures and temperatures for both components, where the relative deviation in the density calculation using the ideal gas model does not exceed the desired value. In addition, on the basis of the mixture theory, such moist air conditions (characterized by pressure, temperature and specific humidity) are searched, on which the accuracy of the calculation meets the required conditions. Subsequently, diagrams are constructed that can be used to help identify the interface between a moist air area that can be described by a simple ideal gas model, and areas where it is necessary to use a more accurate model for one of the components.
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    Possibility of derivation of energetic state variables from simplified BWR thermal state equation for water and water steam
    (2017-01-01) Vestfálová Magda
    Thermal equation of state, along with the basic heat capacities are the most important documents needed to description the behavior of substances. Any other thermodynamic properties of a substance can already be deduced from these relations. The aim of this paper is to derive the dependence of energetic properties of water steam on the temperature and density from simple thermal equation of state based on original BWR thermal equation of state which describes the behavior of H2O in the gaseous phase in region of usual pressures and temperatures with sufficient accuracy.
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    TECHNIQUE FOR DETERMINATION OF PHASE CHANGES IN MOIST AIR FLOW IN A BLADE CASCADE
    (2018-01-01) Vestfálová Magda; Šafařík Pavel; Šimurda David
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    Thermal equation of state BWR for water and water steam
    (2016-01-01) Vestfálová Magda; Petříková Markéta
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    Thermodynamic properties of real gases and BWR equation of state
    (E D P SCIENCES, 17 AVE DU HOGGAR PARC D ACTIVITES COUTABOEUF BP 112, F-91944 CEDEX A, FRANCE, 2015-01-01) Vestfálová Magda
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    Thermodynamics of moist air
    (nakladatelství ČVUT, 2016-01-01) Vestfálová Magda; Šafařík Pavel
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    Tools for determination of humid air state for experimental and numerical investigation of equilibrium physical processes
    (2017-01-01) Vestfálová Magda; Šafařík Pavel
    The presented article deals with the solution of processes in humid air involving the particular elimination of moisture contained in the air. In the case that all of the moisture in the humid air is in the gaseous state, it is a homogeneous mixture. In the case that a part of the moisture in the humid air is in the state of liquid or solid, it is a heterogeneous mixture. In the presented paper processes, where the partial elimination of moisture from humid air (either as a liquid or as a solid phase) can appear, are studied. They are the processes, where the moist air mixture becomes heterogeneous. Based on the theory of ideal mixtures the computational methods enabling determination of the thermodynamic state of the beginning of the elimination of moisture are developed. The thermodynamic properties of dry air and water are applied. Subsequently there are designed diagrams that can be used as an aid to identify interfaces of homogeneous and heterogeneous humid air.