Abstract:At this study an attempt for the theoretical approach of the Reynolds number effect of air flow to the particle collection efficiency of a fibrous filter with cylindrical section will be made. Initially, a report of the air filtration models to fibrous filter media will be presented along with an explanation of both the parameters and the physical quantities which govern the air filtration process. Furthermore, the resulting equation from the mathematical model will be applied to a real filter medium and the characteristic curves of filter efficiency will be drawn. The change of a filter medium efficiency with regard to the Reynolds number of air flow that passes through the filter, derived from the curves, will be studied. The general conclusion that we have is that as the Reynolds number of filtered air increases, the collection efficiency of the filter decreases.

The scope of the specific study is the statistical prediction of the annual carbon dioxide use emissions due to the operation of computed tomography (CT) scanners and magnetic resonance imaging (MRI) units in hospitals, health units and diagnostic centers, for the period between 2018 and 2030, in 120 countries across the world. The main sources of information for this study comprise statistical data from international organizations, scientific articles and measurements. The basic calculation tool of the study is a mathematical model, modified in such a way so that the calculations can be carried out using the available statistical data. In the final stage of the study, the functions that predict the carbon dioxide use emissions in relation to the years, will be extracted. Furthermore, all the errors and uncertainties of the mathematical model will be estimated. The conclusion, arising after implementation of the calculations, is that the carbon dioxide use emissions of CT scanners and MRI units are expected to grow by 30%, i.e., from 0.344 gigatonnes in 2018 to 0.497 gigatonnes in 2030.

The scope of the specific study is the extraction of mathematical relations which correlate the nominal capacity with capacity range of an inverter air conditioner unit with variable speed compressor under standard conditions, that is, measurements of minimum and maximum power of air conditioner under specific indoor and outdoor temperatures. Initially, the necessary statistical information for nominal minimum and maximum capacity will be collected from a sample of 544 different inverter air conditioner models. Furthermore, the regression analysis and the change curves of capacity range with regard to the nominal capacity for cooling and heating operation will be drawn. Also the change of turndown ratio with regard to the nominal capacity and capacity range of air conditioners will be studied. The conclusion that arises is that the maximum capacity and capacity range are varied linearly for cooling and heating operation. There is no clear indication for turndown ratio due to low correlation coefficient of the mathematical model.

Abstract:In the present study the two-dimensional computational simulation flow of hot exhaust gases which are passed inside an electrostatic precipitator will be carried out. Initially, the theoretical background and necessary equations from fluid mechanics will be described. These equations will be used by software for flow simulation. Furthermore, are presented the design of precipitator through which the exhaust gases are passed. In the next step follows the declaration of various parameters of simulation on the software and finally the necessary images of the computational simulation for two case studies will be extracted. The general conclusions that arise are that the maximum flow velocity of exhaust gases prevails only at the beginning of the entrance of the precipitation element. There are different velocities in all other parts of precipitation element. When the exhaust gases approach the collecting electrodes within the element, their velocity is decreased.