Milan Šekularac

To develop a reliable method for modeling fire case scenarios within the road tunnels and observing the effects of the skewed velocity, experimental and numerical approach is used. Experimental results obtained from a laboratory tunnel model installation, are used to define geometry and boundary conditions. The result for the overall ventilation performance is compared to the available cases, for empty tunnel and stationary bi-directional vehicle traffic. For a unidirectional traffic road tunnel, in traffic loaded conditions, with a ventilation system based on axial ducted fans, the numerical simulation is used to determine the flow and temperature fields, the ventilation efficiency (efficiency of momentum transfer), and to assess the shape of the velocity distribution. The effect that a skewed velocity distribution can have on the resulting thermal and pollutant fields (CO2), smoke backlayering and stratification, is evaluated using numerical simulations, for the model-scale tunnel...

ABSTRACT:
Tehnike koje proizvode delove aditivnim metodama (postepenim dodavanjem čvrstog materijala) spadaju u brzu izradu prototipa. Brzo izradjivanje prototipa revolucioniralo je izradu prototipova sa ključnom razlikom u odnosu na konvencionalne metode – supstraktivne metode. Prototip je sastavni deo inženjerskog dizajna proizvoda i učestvuje u ukupnom procesu razvoja novog proizvoda. On predstavlja preliminarnu verziju krajnjeg proizvoda i njegova svrha je testiranje ili analiza principa rada kao i procenu dizajna. Korišćenje tehnologije 3D štampe za izradu prototipova značajno se smanjuju vreme i troškovi proizvodnje. 3D štampa omogućava prevazilaženje ograničenja sa kojima su se ranije suočavali inžinjeri pri dizajnu alata, tako da će se u ovom radu primenjivati CAD softver i 3DP. U ovom radu osvrt će biti na dizajniranju CAD, inžinjerstvu CAE, brzoj izradi prototipa RP i reverzibilnom inženjeringu RE male vetro turbine. Takođe, u radu je izvršeno i generisanje prototipa od realnog materijala, primenom tehnologija 3DP i laboratorijska ispitivanja odnosno određivanje snage na vratilu turbine.

Ključne reči: vjetro turbina, prototip, rapid prototyping, 3DP

Emissions from individual furnaces such as stoves and boilers in various central heating systems give a significant contribution to air pollution. In combination with specific meteorological conditions, primarily temperature inversions, pollutant concentrations can significantly exceed the permitted values over longer periods of time, which undoubtedly results in adverse health impacts. As an illustrative example, for the mentioned reasons, the city of Pljevlja in the north of Montenegro is the most polluted city in the country. In order to determine the actual contribution to air pollution of large central heating boilers (300 to 500 kW), two objects whose heating systems are most common in Pljevlja are selected for testing. Flue gases emissions measurements are carried out on selected boilers on the spot, in accordance with standard reference methods. Two sets of measurements were made on each furnace: first with coal firing, because coal is predominantly used today as a fuel, and then, after cleaning the furnace, with briquette firing, because briquette is considered as possible substitute fuel. This paper presents the results obtained during the comparative measurement. In addition to determining the actual contribution of large boiler rooms to the current air pollution situation, the aim of those measurements is to assess the potential for reducing pollutant emissions by replacing coal with briquettes. Despite numerous factors affecting the measurements, the results show that the total emissions are significantly lower when briquettes are used as fuel, in particular in terms of SO 2 , PM and heavy metals emissions.

Pljevlja is a city with the most polluted air in Montenegro. Emissions from individual furnaces and small city boilers give a visible contribution to air pollution. In order to determine their actual contribution, three manual coal fired boilers, which are most common in boiler rooms in Pljevlja, are selected for testing. Flue gas emissions measurements are carried out on selected boilers in accordance with standard reference methods. The aim of the study is to determine the quantities and contents of harmful and hazardous substances in the flue gases that occur in combustion process of coal in boilers, when they are operated in the usual regime. The paper presents the obtained results and describes the difficulties that we encountered during on field measurements.

KEY WORDS: emissions, flue gas, air pollution, coal fired boiler.

Abstract: Pljevlja is a town with the most polluted air in Montenegro. Emissions from individual furnaces
such as stoves and boilers in small central heating systems in family homes give a visible contribution to
air pollution. In order to determine their actual contribution, stoves and boilers, which are most common in
Pljevlja, are selected for testing. Flue gas emissions measurements are carried out on selected boilers, on
site, in accordance with standard reference methods. This paper presents the results obtained during the
testing of two individual furnaces. Two set of measurements were made on each furnace: first with coal
firing because coal is predominantly used today as a fuel, and then, after cleaning the furnace, with briquette
firing because briquette is considered as possible substitute fuel. The aim of those measurements is to
determine the contribution of individual furnaces to the current situation in terms of air pollution, as well
as to assess the possibility of reducing emissions of pollutants when coal is replaced by briquettes.
Keywords: emissions, flue gas, air pollution, coal, briquette.

Various approximate methods, and guidelines, are followed by tunnel-ventilation designers in the process of sizing the ventilation system. Of particular importance are the heat transfer coefficients used in prediction of the temperature distribution during a fire event. This strongly affects the ventilation exerted trust, and induces a chimney-effect pressure in sloped tunnels. For this purpose, a one-dimensional numerical solution approach is used in this work to evaluate their values. In addition, processing of a selected tunnel-fire-test from the literature data is also used in order assess the heat transfer coefficients values from realistic fire-tests. The results are discussed for final conclusions.

To investigate air flow in longitudinally ventilated traffic tunnels, a scaled model of a typical road-traffic tunnel with an appropriate ventilation system based on axial ducted fans, is designed and built in the Lab. The focus of this paper is the airflow in a bi-directional traffic, two-lane tunnel. At the scale ratio of approx. 1:20, at 20.52 m length it represents ≈ 400 m of a realscale tunnel. The model consists of two parallel tunnel tubes, where the main tunnel (with a hydraulic diameter of ℎ1 ≈ 0.4 m) has the geometry of a scaled road traffic-tunnel. The second tunnel (ℎ2 ≈ 0.16 m) has a smaller size and is circular in cross-section, used only to simulate airflow towards an evacuation tunnel tube. Thus the two tunnels are connected by the evacuation passages, equipped with adjustable escape doors. By a combination of experimental and numerical work, the air flow-field and the performance of the ventilation system are investigated. The velocity field and its turbulence properties exiting the fans were determined experimentally using hot-wire anemometry. These data were further processed to be used in the tunnel flow computations by CFD. The efficiency of momentum transfer (, Kempf factor) of the longitudinal tunnel ventilation is determined. The effect that the imposed boundary conditions and the level of their detail, have within a CFD computation of tunnel airflow, with respect to accuracy, velocity distribution and computed. Finally a traffic-loaded (traffic "jam") case of flow is studied through experiment and CFD. The difficulty in assessing the required thrust of the plant in traffic-jam tunnel conditions is discussed, and the ventilation efficiency is estimated. Based on later results, the two limiting shapes of axial velocity distribution with respect to height above the road, in this type of tunnel and traffic, are estimated. The last result can be used as a realistic boundary condition (as inlet b.c. and/or initial condition) for numerical studies of flow and fire scenarios in such tunnels with the traffic load critical for design.

One of the important factors influencing the thermal performance of buildings is the leakage of the envelope. When it comes to Montenegro, although there is a formal airtightness requirement, air permeability tests are not mandatory and therefore there is a lack of data in this regard. This paper reports the results of fan pressurization tests on a single apartment in a multi-family residential building before and after replacing the windows. The replacement of old wooden windows with new UPVC ones, provided that the installation is carefully supervised, proved to be an effective air tightening measure, as it resulted in a reduction of air change rate at the reference building pressure from 6.25 h−1 to 0.77 h−1, or by nearly 90%. The energy impact of air leakage was evaluated using the national software for calculating the energy performance of buildings based on the DIN V 18599 methodology. Calculations showed that by reducing infiltration, significant energy savings for heating ca...

Experimental installation as well as experimental and numerical investigations of the road tunnel ventilation are presented. Since recently, two modern single tube two-way traffic road tunnels, 4.2 km and 1.4 km long, are in use in Montenegro. In order to analyse the flow of the first one in detail, a smaller scale model corresponding to a 400m length of the real structure, has been constructed in the Laboratory of Faculty of Mechanical Engineering in Podgorica, Montenegro. It is equipped with a similar in geometry and function, scaled, ventilation system based on aircraft-modeling jet-fans powered by electric motors. The main tunnel tube is ventilated longitudinally, while the secondary (smaller evacuation tunnel) could be over-pressured with respect to the main tunnel, in the case of a hypothetic accident situation. Cross passages connect the two tunnels. The ventilation efficiency, pressure drop, and transient regime under changing air directions are experimentally and numericall...

To investigate traffic tunnel ventilation flows, a scaled model of a traffic tunnel with longitudinal ventilation system based on ducted fans is used. Flows in tunnels are influenced by tunnel geometry, fan characteristics, ventilation operation scenario, vehicle traffic, atmospheric factors, etc. To analyze flow fields of tunnels in detail, knowledge of tunnel jet-fan properties and turbulent flow characteristics at the fan exit are required, and can be used as input data for CFD boundary conditions of tunnel flow computation. For this purpose experimental measurements were done using the hot wire anemometry technique. The obtained results, trough ensemble-averaged and time averaged profiles of all velocity components, turbulence intensity, turbulent kinetic energy, integral flow length scales, available Reynolds stresses, Turbulent kinetic energy production rates and the fan thrust performance, are presented. These data allow us to analyze in more detail the influence of fan flow ...

In this paper a seasonal effect of a air-to-ground type geothermal heat exchanger is analyzed, in the climatic conditions of the city of Podgorica, for a period of heating and one cooling season, separately. A CFD analysis of the problem for the period of one heating and one cooling season separately has been conducted, within which the exchanger operates continuously (without daily interruption). The processed numerical data are presented in the form of characteristic temperature changes within one season and the system efficiency (COP). Exergy flow analysis for the system is given as well. Ovim radom analiziran je sezonski učinak geotermalnog razmjenjivača toplote zemlja-vazduh (engl. air-ground heat exchanger) za grejni i rashladni režim rada, u klimatskim uslovima Podgorice. Izvršena je CFD analiza problema za period jedne grejne sezone i posebno za period jedne sezone hlađenja, u toku kojih razmjenjivač radi bez prekida. Obrađeni podaci su prezentovani u formi promjena karakter...