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Multicriterial Tool for Analysis and Predict Human Thermal Stress
Řehák Kopečková, Barbora ; Soukup,, Radek (referee) ; Kolářová,, Jana (referee) ; Jícha, Miroslav (advisor)
The thesis is concerned with the development of a multi-criteria tool capable of determining, for given input conditions, the most appropriate model for predicting the thermal state of a person in a protective suit, based on developed objective decision scheme. Four heat stress indices or physiological models were selected for the development of this tool: PHS (Predicted Heat Strain), IPHS (Individual Predicted Heat Strain), Gagg's 2-node model and the FMTK model. The algorithms of PHS, IPHS and Gagge were implemented in Matlab. Subsequently, all 4 models were validated against the experimental results. Based on the results of the validations, the applicability of these models for predicting human heat stress was verified. For some models, the applicability conditions were possible to extend. The accuracy of rectal temperature prediction was the main criteria. Furthermore, based on the results of the validation studies, metrics were selected to build an objective decision system. This was used to select the most appropriate model for the given environmental conditions. In the cooperation with SÚJCHBO, the data for model validation were delivered: 140 tests were carried out for 4 protective suits (FOP, Tyhem, Tiger, OPCH) and 4 ambient temperatures (-10, 5, 25 and 35 °C). 12 test persons were involved, 6 male test persons aged 29-53 years, 170-187 cm tall and weighing 69-92 kg, and 6 female test persons aged 28-49 years, 158-176 cm tall and weighing 56-71 kg. In total, 1987 simulations have been carried out using selected models, for different initial values of rectum and skin temperature, and for different estimates of metabolic activity. A look-up table was created to find the most appropriate model for the given conditions according to the inputs to the multicriteria tool via a decision scheme, based on the evaluation of the results of the simulations against the experiments in terms of the MAE (Mean Absolute Error) and the difference between the predicted and measured rectal temperature at the end of the test. Finally, the resulting multicriteria tool was created in Excel, including a graphical interface for entering values.
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Modeling of Liquid Film Instabilities with Subsequent Entrainment of Droplets
Knotek, Stanislav ; Kozubková, Milada (referee) ; Čermák, Libor (referee) ; Jícha, Miroslav (advisor)
This dissertation deals with instabilities of thin liquid films up to entrainment of drops. Four types of instabilities have been classified depending on the type of structure and process on the liquid film surface: two-dimensional slow waves, two-dimensional fast waves, three-dimensional waves, solitary waves and entrainment of drops from the film surface. This thesis analyzes the physical principles of instabilities and deals with the mathematical formulation of the problem. Shear and pressure forces acting on the surface of the liquid film are identified as the cause of instabilities. Mathematical models for predicting instabilities are demonstrated using approaches based on solving the Orr-Sommerfeld equation and the equations of motion in integral form. Models of shear and pressure forces acting on the surface of the film and selected models of film thickness are presented. The work is focused on the prediction of the initiation of two-dimensional waves using the integral approach. Shear stress and pressure forces acting on the liquid film surface have been modeled using the simulation of air flow over a solid surface. Finally, criteria for drop entrainment are presented with their dependence on air velocity and film thickness.
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Aircraft windshield blowing: solution and design possibilities
Šamša, Petr ; Fišer, Jan (referee) ; Jícha, Miroslav (advisor)
My thesis is considering with aircraft windshield blowing for airplanes designed according to CS-23 regulation. The first part introduces the size of precipitation clearing area in connection with CS-23 regulation and report SAE AIR805C. Next chapter describes a few possible design solutions which can be potentially used for windshield precipitation. There are also other methods analysed in that part. There are not only the casual systems like windshield wipers but some more rare or new technologies too. It can be some fluid repellent surfaces or blowers in that category. The third part deals with jet blast system in detail. There will be a design calculation for airflow conditions which are important for the correct function. The last quarter of this thesis mentions the experiment what should compare the theoretical computations from the third part with the real values.
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Transport and Deposition of Aerosol in Human Respiratory Tract
Elcner, Jakub ; Kratochvíl, Zdeněk (referee) ; Volavý, Jaroslav (referee) ; Jícha, Miroslav (advisor)
One of approaches in treatment of respiratory system diseases is the use of drug particles suspended in air in the form of aerosol. It is a fast and non-invasive method for the delivery of medicine into tracheobronchial tree or bloodstream. Although the method of the medication dosage by means of inhalers or nebulizers is well known, the effectiveness of that approach is still an actual issue. A significant amount of drugs delivered with the use of the medication dosage never reaches its primary destination and the drugs deposit in antecendent areas of respiratory tract where their presence is not required. This thesis deals with a problem of the passage of monodisperse homogenous aerosol with micron-size particles through the upper parts of the respiratory tract. This work was created with the use of numerical simulations carried out by means of the finite volume method in the commercial code based on computational fluid dynamics. Turbulence was modelled using the Reynolds averaged Navier–Stokes equations with the two-equation eddy viscosity k-omega SST model. The main output of the thesis is the analysis of airflow in two respiratory regimes. Stationary and cyclic cases of the flow behaviour were considered and the validation of simulated results with experiments performed on similar geometries was carried out. Furthermore, the review of simplified lung models and their geometries was made and the acquired results were used for the calculation of air distribution in the respiratory tract. The last part of the thesis deals with the calculation of particle deposition and with the analysis of the results.
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A method for the solution of non-spherical (fiber) particles deposition by means of the Fokker-Planck equation for ODF in a laminar flow
Kopečková, Barbora ; Knotek, Stanislav (referee) ; Jícha, Miroslav (advisor)
The Bachelor's thesis deals with a deposition efficiency for a fibers by various mechanisms of a deposition. It explains deposition efficiency by diffusion, by sedimentation and by impaction. The implementation of Peterlin's analytical solution for calculation of the ODF, which is used for individual efficiencies solution, is also mentioned. Afterwards, the thesis summarizes formulas for calculation of particular efficiencies derived for spherical particles and recomputation appropriate parameters for fibers. The purpose of the thesis is to create graphs, which illustrate deposition efficiencies dependence by various mechanisms on the aspect ratio of fibers. Another goal is the graphs creation, which shows juxtaposition for various breathing modes for given deposition mechanisms. The software MATLAB is used for the whole calculation process and graphs plotting.
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Influence of boundary walls on the flow from the ventilation outlet
Molčan, Filip ; Jícha, Miroslav (referee) ; Jedelský, Jan (advisor)
The goal of this work is to experimentally assess the influence of limiting walls of Škoda Octavia 3 automobile cabin to the air jet flowing from the right-front situated automotive vent which is part of a car dashboard. The experiment is performed by the smoke visualization method. There is a single construction option measured for an experiment. The setup of the vanes direction and the air flow rate are modified for this option. The experiment is divided into two phases. In the first phase, the visualization of the free air flow is conducted. In the second phase, exit plates are constructed and consequently, the visualization of the wall-jet flow is conducted. The results of both are compared to each other. The results imply that the influence of the surrounding surfaces must be taken into account with the increasing flow rate for the vanes set in the direction of upper-right, middle-right, and middle-middle. There is a direct interaction between the flow and exit plates (the flow impact, the Coanda effect). The free flow does not contain the information about the mutual interaction between the flow and the exit plates, as it is in the case of the wall-jet flow. In the case of the wall-jet flow, the opening of the flow takes place due to the effect of the impact and the subsequential suction caused by the Coanda effect. The exit plates substituting the car dashboard and the front window contribute to the prevention of the air intake from surrounding space and consequently to earlier flow opening from the vent. The present work also contains the measurement methodology and the image evaluation, the comparison with previous free flow measurements (70% match) and the comparison to the measurement of hot-wire anemometry method.
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Method for the solution of conduction heat transfer in Phase change material with nanoparticles
Kopečková, Barbora ; Knotek, Stanislav (referee) ; Jícha, Miroslav (advisor)
This master thesis deals with problematic of the heat convection in phase change materials (PCM) and PCM with nanoparticles. The derivation of stationary and non-stationary equations for 1D, 2D and 3D heat convection are described in detail. The finite element volume method is used for solution to these equations, of which principle is described carefully. The aim of this thesis is model development for 2D solution to temperature distribution at heat convection in PCM and influence assessment of nanoparticle implementation into material on given temperature distribution. Software MATLAB was used for model development, solution and plotting graphs.
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Coupling of the Models of Human Physiology and Thermal Comfort
Pokorný, Jan ; Masaryk, Michal (referee) ; Kratochvíl, Zdeněk (referee) ; Jícha, Miroslav (advisor)
The thesis deals with car cabin environment and thermal comfort inside. A car cabin heat load model was developed in Dymola/Modelica to investigate influence of ambient environmental parameters. The model was validated on the data set of eight test cases measured in a climatic chamber and in a real traffic. The main objective of the thesis was to develop a human thermal comfort model suitable for non-homogenous environments and for a car cabin environment especially. The Coupled model of human physiology and thermal comfort was developed in Dymola/Modelica. The model allows predicting an overall human thermal comfort from local boundary conditions representing ambient and personal factors. The model was validated by 16 test cases taken from experiments in literature. Moreover three test cases were created in Theseus-FE to consider an asymmetrical heat load from Sun rays inside a car cabin. Prediction of the Coupled model was compared with Fiala model and experimental data. The Coupled model predicted mean skin temperature for moderate activities in neutral and warm environment well. In cold environment a predicted core temperature was very affected by ambient temperature and during high activity exercises, the predicted mean skin temperature was too high.
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