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Heat transfer in solar energy equipment
Hylas, Martin ; Jegla, Zdeněk (referee) ; Babička Fialová, Dominika (advisor)
Photovoltaic panels are an efficient device for converting solar energy when exposed to high solar radiation intensity, which is, however, associated with a high ambient temperature. The high operating temperature of a photovoltaic panel has a negative effect on the efficiency and lifetime of the device. The first part of this thesis presents the current state of the art in the field of active and passive cooling methods for photovoltaic panels. The main metrics for evaluating the effectiveness of cooling systems are the cooling rate and the power gain of the photovoltaic module. The research shows that significant reduction of temperature effects can be achieved by support systems, but based on the experimental work to date there is no unified view on the applicability of the cooling devices in practice. Investment and operating costs are a significant barrier to the use of these systems by the general public. A possible solution to efficiently generate electricity and utilise otherwise wasted heat is to combine the functions of photovoltaic panels and solar thermal collectors into hybrid photovoltaic-thermal collectors. The tubular distribution system is an integral part of these installations. From a design point of view, these are simple systems, naturally subject to uneven distribution of the working medium, which results in a decrease in the efficiency of the entire device. In the second part of the thesis, the functionality of analytical models to predict the distribution of the working medium in a K-type distribution system is verified. The results of the comparison of predicted data with experimentally measured values show that the predictive ability of the analytical models is strongly dependent on the method of determining the value of hydraulic resistance (local losses).
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Detection of QRS complex in experimental ECG data
Brandejs, Jakub ; Harabiš, Vratislav (referee) ; Vítek, Martin (advisor)
In this paper, called Bachelor thesis, I proposed a QRS complex detector based on wavelet transformation where biorthogonal wavelet bior1.5 was applied with use of Matlab. The detector works with antisymmetry of the wavelet to detect minimum/maximum or maximum/minimum pairs and singularity between them. Results of this detector were evaluated on the CSE database. The detector was reworked to be able to detect experimental QRS complexes.
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Detection of QRS complex in experimental ECG data
Bucsuházy, Kateřina ; Ronzhina, Marina (referee) ; Vítek, Martin (advisor)
This Bachelor work deals with QRS complex detection. The theoretical part of the presented work is focused on summary of selected methods of QRS complex detection. There is described in detail wavelet transform, which is used for realization of QRS complex detector in Matlab. Specifically is used redundant dyadic discrete wavelet transform and biorthogonal wavelet with odd symmetry bior1.5. The algorithm was evaluated on the standard CSE database. The detector was modified to be able to detect QRS complexes in experimental data.
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Mathematical models for incompressible non-newtonian fluids with non-monotone dependence of shear stress on shear rate
Perlácová, Tereza ; Průša, Vít (advisor) ; Málek, Josef (referee)
We investigate recently developed implicit constitutive theory and its implication into the modelling of fluids. We base the work on the literature search that is focused on the S-shaped shear stress-shear rate experimental data. The materials that exhibit such a behavior are found to be colloidal suspensions and surfactant solutions. The work summarizes microscopical theories explaining the shear-thickening, the shear-thinning and the shear-banding phenomena that arise in these materials. The theories reveal that the unusual behavior is due to the separation of the fluid into various bands in shear stress-controlled measurements. The extracted experimental data from the literature are fitted with several one-dimensional implicit type relations. Finally, we propose an example of a fully three-dimensional implicit constitutive relation with focus on the normal stress differences effect. The work demonstrates benefits of the implicit constitutive theory for modelling of complex fluids. 1
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Simple Equipment for Measurement of Total Pressure Tested on Poly(ethylene glycol) + Water System.
Pavlíček, Jan ; Bogdanić, Grozdana ; Wichterle, Ivan
In this work, new equipment designed for total pressure determination in mixtures where one of component is not volatile, such as polymer + solvent systems, is presented. It enables measurement of pressure above solutions in a wider concentration range. The equipment has been tested and calibrated using vapour pressure of pure water. It consist of thermostat with temperature measurement (AΣΛ, model F250), 100 ml vessel for solution with magnetic stirrer with a very strong driver, and of heated manifold for charging, degassing and for pressure measurement. Pressure is measured with use of absolute heated capacitance unit MKS Baratron (pressure range 1000 Torr = 133 kPa). Mixtures were prepared by weighing to obtain volume of 50 ml, approx.
Fulltext: content.csg - PDF Plný tet: SKMBT_C22016090211390 - PDF
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