Search

The paper presents an experimental analysis of the relationship between local thermal comfort and productivity loss in classrooms. The experimental investigation was performed in a real university classroom during the winter semester in Belgrade. Measurements were taken for four scenarios, with different indoor comfort conditions. Variations were made by setting the central heating system on/off, adding an additional heat source to provoke higher indoor temperatures, and measuring the radiant asymmetry impact. Innovative questionnaires were developed especially for the research, in order to investigate students' subjective feelings about local thermal comfort and indoor environmental quality. Local PMV and PPD indices were calculated using data measured in situ. The results were compared to existing models recommended in literature and European and ASHRAE standards. Student productivity was evaluated using novel tests, designed to fit the purposes of the research. Surveys were conducted for 19 days under different thermal conditions, during lectures in a real classroom, using a sample of 240 productivity test results in total. Using the measured data, new correlations between the PMV, CO2, personal factor and productivity loss were developed. The research findings imply that local thermal comfort is an important factor that can impact productivity, but the impact of the personal factor is of tremendous importance, together with CO2 concentration in the classroom. © 2018 Serbian Society of Heat Transfer Engineers.

Serbia is situated at Balkan Peninsula, and currently majority of the territory is under warm temperate fully humid climate type with warm summers (Cfb type, according to Koppen-Geiger Climate Classification). Observed changes in climate conditions since 1961 until present time show significant increase in temperature change and change in precipitation patterns. Disturbances in heat conditions, which are recorded to affect human health, agricultural production and forest ecosystem, are priority in climate change analysis and application in adaptation planning. Future change analysis show accelerated increase of temperature by the end of the 21st century, which proves the needs for immediate measures for mitigation of negative impacts. Temperature increase averaged over the territory of Serbia is 1.2 degrees C for the period 1996-2015 with respect to the period 1961-1980, with highest increase of maximum daily temperature during the summer season, 2.2 degrees C. Using high resolution multi-model ensemble approach for analysis of the future changes with respect to the base period 1986-2005, in compliance with Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (ARS), it is estimated that temperature may increase by 1.9 degrees C according to Representative Concentration Pathway 4.5 (RCP4.5) scenario and by 4.4 degrees C according to RCP8.5 by the end of the century. Spatial distribution of temperature increase, intensification of high precipitation events and decrease of summer precipitation, show intrusion of subtropical climate over the Serbia and increase of high temperature and high precipitation risks. Results presented in this paper, using high-resolution multi-model ensemble approach, provide climate change information for short term to long term planning in different sectors of economy and preservation of human health and environment.

Office buildings have high standards for lighting requirements, which greatly contribute to high lighting energy consumption. Daylight utilization is one of the means to reduce it. The goal of this paper is to evaluate daylight utilization po-tentials in Belgrade climate in order to generate initial design guideline for high-ly glazed small, individual office spaces. Daylight availability and its lighting en-ergy implications are analyzed using computer simulation tool DIVA for Rhino. Selected individual office space is modelled as a narrow rectangular space, sidelit and highly glazed. Parametric analysis was carried out for: four different glazing ratios (50, 60, 70, and 85%), four glazing types with different visible transmittance properties (80, 72, 62, and 54%), and four different major orienta-tions. Since this analysis is evaluating daylight utilization potentials, no shades or external obstructions were considered. The major results of this study indicate high potential for daylight utilization in office buildings in Belgrade. Daylight utilization in single offices is reaching its maximum in model with 70% window-to-wall ratio for all office orientations except north orientation, where daylight utilization is reaching its maximum at maximum window-to-wall ratio. Also, north orientated spaces have highest benefits from utilization of useful diffuse daylight. Direct sunlight and size and shape of façade aperture above working plane are determining factors for utilization of daylight in office spaces.

Thermal energy demand in the residential building sector represents a big challenge for Serbia. In order to understand how to reduce this demand, and thereby avoiding GHG gas emissions, a bottom-up simulation model was developed. The model built the business-as-usual and two decarbonization scenarios up to 2030. For each scenario, such results as useful and final energy consumption, associated CO2 emissions, energy costs, investment costs and others were prepared at each level of the building stock segmentation. To develop such a detailed model, the topology of the residential building stock was developed and used as an input. For each individual building type, three retrofit packages of different stringency were analyzed. The paper delivers several important messages for the decarbonization of Serbia. First, it argues that the level of thermal energy services consumed by Serbian households is inadequate to address their needs. Second, the households of Serbia are likely to consume more wood than it was reported by national energy balances. Third, thermal energy efficiency retrofits can significantly reduce household energy demand at the same time as offering higher thermal comfort. However, the required investments are high and therefore benefits beyond energy cost savings should also be considered in order to make the transition to the low energy building stock economically feasible.

Developing countries are facing numerous challenges in the process of providing adequate health care to often deprived and diminished social groups. Being a country made up of a mainland territory and five islands in Gulf of Guinea, almost entirely covered by tropical rainforest, with poor road infrastructure, Equatorial Guinea is a showcase of various obstructions in developing effective health care system. The paper explores guidelines for creation of model regional hospital, commissioned by Ministry of Health and Social Welfare, with the aim of achieving high level of replicability through minor program and site-specific adjustments. The demonstrated strategies are applied on a local hospital designed to provide all basic types of health services while retaining a high level of technical independence. The architectural concept was formulated aiming to maximize the use of natural ventilation, daylight and rainwater management, leaving the operation block, laboratory and intensive care unit practically the only parts of the structure that would need mechanical air conditioning. The potential and effectiveness of use of photovoltaic units in enhancing hospital's resilience through on-site energy production was explored. The structure was designed having in mind local climate, culture and customs, thus offering a possibility of strong integration with local community. The building technology was thought over to enable efficient and cost-effective construction and proper resilience for tropical rainforest environment. The result is a structure providing for contemporary, high quality medical service, interpreting local climatic and cultural contextual premises through modern architectural expression.

By harmonizing national legislation to European codes concerning energy efficiency in building sector, Serbia took commitment to improve energy efficiency of national government buildings. Following the Directive 2012/27/EU principles, refurbishment of this part of building stock is recognized as a leading example in long-therm process of applying energy efficiency regulations at national level. Initial steps in implementation of adopted energy efficiency principles were made in Serbia during 2015, when first energy certificates for three most valuable buildings of national authorities (Government building, The National Assembly, and the Palace of Serbia) were issued. This paper will present results obtained during energy-assessment and energy-certification process of this particular buildings, showing at the same time their specificity, that pretty much traces possible category and range of proposed energy refurbishment scenarios.

Using RES is one of the most important characteristics of the sustainable and resilient development. Nowadays, need to minimize CO2 emissions is obligatory, especially in the sector of urban and architectural planning, since in Serbia approximately 50% of produced energy is spent in buildings. The CO2 emission, in urban structures, can and must be reduced at the different levels: building level, block, and city level. For the city of Kragujevac, based on urban parameters defined in General Urban Plan, typical urban block was chosen and typical building structure developed. Calculation were made, based on recommendations developed by the Ministry of mining and energy and Serbian regulations, for the energy needed for domestic hot water preparation. In this paper, the influences of architectural and urban parameters on the use of solar thermal collectors at the typical building and urban block level is investigated. Recommendations are prepared for principles of urban and architectural design in order to enable the use of collectors for domestic hot water preparation and in that way CO2 emission reduction. Developed methodology for the city of Kragujevac can be applied in defining design principles in whole the country and Balkans region, not only for the use of solar thermal collectors but also for the use of other RES.

Activities related to buildings contribute to a large degree to environmental degradation. It is necessary to reduce the negative environmental impact and resource consumption throughout the life cycle of the building. The aim is to optimize building performances in accordance with the integrated design objectives. The building structure, along with other elements of architectural space, determines the performances of the building. The building structure should be designed and evaluated as a sub-system of the building, whose behaviour is directed towards the aim of system-building ecological quality. This paper deals with the analysis of structural design in accordance with integrated design objectives, which are derived from quantitative and qualitative indicators of ecological quality of building, within the criteria of environmental protection throughout the life cycle of the building. The overall objective is to reduce harmful emissions to the air, water and soil, as well as to increase the efficiency of resource use, that is, to reduce the intensity of their use. Based on subject analysis, the environmentally-based criteria for the design and evaluation of building structures are derived, in the function of creating the environmentally acceptable building solutions. The present analysis points to the necessity of applying a complex and systemic approach to structural design, in function of achieving the ecological quality of buildings.

Following the guidance set by the Directive on the energy performance of buildings (recast) (EPBD2), current regulations in Serbia which refer to the issue of energy efficiency and energy certification of buildings provides an opportunity of certification of selected unit of a building, such as a dwelling. This measure was set in order to make it possible for owners or tenants of the building or the building unit to assess and compare its energy performance. From the user's perspective this measure is very important since, apart from reviewing the quality or the deficiencies of space in which they live, it would be an important parameter of economic evaluation of the apartment in the future. As energy performance of the apartment is not a priori identical to that of the whole building, the paper will analyze and compare these values for different positions in a horizontal and vertical plan of the same apartment within the building. Comparison of the results obtained for individual dwellings and for a building as a whole, will provide insight into the extent to which the disposition and the orientation of the apartment affect its energy performance.

The aim of this research is to examine and analyse the thermal characteristics of the facade modular element. The possibility of optimization of the facade coating with vegetation is examined experimentally in this research, with the aim of improving the thermal characteristics of the facade wall. This element is made of perlite concrete in which the greenery is implanted. The scope of the research is experimental and theoretical testing the possibility for optimizing the facade coating with vegetation. The energy specificities of modular vegetation elements and their contribution to the improvement of the thermal properties of the facade wall are analysed in the experimental part of the research, the elements of vegetation are treated as the elements which influence the decrease in surface temperature of the facade coating. The modular elements in this research are placed on a reference wall surface facing the South. The methodology presented in this paper is based on the study of climate characteristics in city of Belgrade, experimental measurements of test models, and comparative analysis with the reference wall. During the experiment, the data on the external climate parameters and the coefficient of heat transfer through the wall were continuously measured. Conducted measurements and analyses show the vegetation influence on the reduction in surface temperature of the outer wall and the heat passage through the facade coating. The experiment used a modular model and several plant species. It is noticeable that vegetative walls with green areas covered by plant shells play an important role in the harmonization of the parameters of the microclimate in relation to the local environment.

Office buildings have high standards for lighting requirements, which greatly contribute to high lighting energy consumption. Daylight utilization is one of the means to reduce it. The goal of this paper is to evaluate daylight utilization potentials in Belgrade climate in order to generate initial design guideline for highly glazed small, individual office spaces. Daylight availability and its lighting energy implications are analyzed using computer simulation tool DIVA for Rhino. Selected individual office space is modelled as a narrow rectangular space, sidelit and highly glazed. Parametric analysis was carried out for: four different glazing ratios (50, 60, 70, and 85%), four glazing types with different visible transmittance properties (80, 72, 62, and 54%), and four different major orientations. Since this analysis is evaluating daylight utilization potentials, no shades or external obstructions were considered. The major results of this study indicate high potential for daylight utilization in office buildings in Belgrade. Daylight utilization in single offices is reaching its maximum in model with 70% window-to-wall ratio for all office orientations except north orientation, where daylight utilization is reaching its maximum at maximum window-to-wall ratio. Also, north orientated spaces have highest benefits from utilization of useful diffuse daylight. Direct sunlight and size and shape of facade aperture above working plane are determining factors for utilization of daylight in office spaces.

The electrostatic precipitator system of the lignite fired 350 MWe unit B1 of Thermal Power Plant Kostolac B has been modernized during 2014. The results of complex in site measurements, performed in the frame of performance control test at the beginning of the exploitation period of the upgraded electrostatic pre-cipitator proved that, under normal and guarantee working conditions of the boiler and precipitator, the emission of particulate matter do not exceed limiting value. After the period of precipitator further adjustments, five series of meas-urements in the frame of acceptance test were performed in accordance with rel-evant standards. This paper presents results of the investigation of particulate matter concentration, laboratory analysis of the lignite, fly and bottom ash sam-ples, working parameters of the unit and upgraded electrostatic precipitator as well as results of the calculations. The averaged mean particulate concentration at the exit of upgraded electrostatic precipitator of the unit B1 during Acceptance test was below guaranteed value. It is confirmed that adjustments of electrostatic precipitator electrical parameters have improved electrostatic precipitator effi-ciency, as well that electrostatic precipitatorcould work highly efficiently in en-ergy save mode with lower power consumption. © 2018 Society of Thermal Engineers of Serbia.

The paper presents an experimental analysis of the relationship between local thermal comfort and productivity loss in classrooms. The experimental investigation was performed in a real university classroom during the winter semester in Belgrade. Measurements were taken for four scenarios, with different indoor comfort conditions. Variations were made by setting the central heating system on/off, adding an additional heat source to provoke higher indoor temperatures, and measuring the radiant asymmetry impact. Innovative questionnaires were developed especially for the research, in order to investigate students' subjective feelings about local thermal comfort and indoor environmental quality. Local PMV and PPD indices were calculated using data measured in situ. The results were compared to existing models recommended in literature and European and ASHRAE standards. Student productivity was evaluated using novel tests, designed to fit the purposes of the research. Surveys were conducted for 19 days under different thermal conditions, during lectures in a real classroom, using a sample of 240 productivity test results in total. Using the measured data, new correlations between the PMV, CO2, personal factor and productivity loss were developed. The research findings imply that local thermal comfort is an important factor that can impact productivity, but the impact of the personal factor is of tremendous importance, together with CO2 concentration in the classroom. © 2018 Serbian Society of Heat Transfer Engineers.

Altering the surface cover of an area causes the change in the environment. By erecting buildings change in the flow of energy and matter through the urban ecosystems occurs creating multiple environmental problems. Built areas exert considerable influence over their local climate, amplifying problems such as heat waves, air pollution, and flooding. Greening the building envelope these problems can be partially mitigated. By combining nature and built areas in their designs, architects and urban planners can respond to these serious human health and welfare issues and restore the environmental quality of dense urban areas. Green living systems are not the only solution for new designs. Retrofitting existing buildings by altering the buildings' surficial properties can reduce buildings' energy consumption in case of older buildings with poor existing insulation. Implementation of green living systems in the building envelope, greening horizontal surfaces with intensive and extensive green roofs or using vegetation in vertical greening systems for façades, is a strategy that provides ecological, economic and social benefits. This review paper presents collected evidence of effects and explores the important role that the green living systems can play in the dense urban areas. Benefits such as heat island amelioration, reduction of buildings energy consumption, air quality and indoor and outdoor comfort conditions improvement, stormwater management and improved water run-off quality, will be mainly considered. © 2018 Serbian Society of Heat Transfer Engineers.

This paper presents the analysis and comparison of energy and environmental properties of various city bus systems: diesel and compressed natural gas internal combustion engines, trolleybus, and battery electric bus. It is based on experimental research on fuel and energy consumption of city buses with aforementioned propulsion systems carried out under similar driving conditions - on the same city bus lines in Belgrade and Novi Sad, and on evaluation of energy efficiency and CO2 emission of real electricity production in Serbia. In this way, "tank-to-wheel" and "well-to-wheel" energy consumption and CO2 emissions of considered bus driving systems have been evaluated and compared. The results show all complexity of the matter since benefits of application of different systems largely depends on bus exploitation conditions and even more of the conditions of electric energy production. The compressed natural gas internal combustion engine compared to the Diesel engine provides obviously benefit in harmful gas emissions. However, CO2 emissions are on a similar level, while energy efficiency is even less. Electric propulsion systems provide undoubtedly benefit in energy consumption, harmful gases and CO2 emissions if tank-to-wheel conditions are considered, but well-to-wheel characteristics strongly depend on the condition of electric energy production. © 2018 Society of Thermal Engineers of Serbia.

Lately, experimental methods and numerical simulations are equally employed for the purpose of developing incineration bubbling fluidized bed (BFB) facilities. The paper presents the results of the 2-D CFD model of liquid fuel combustion in BFB, applied for numerical simulation of a fluidized bed furnace. The numerical procedure is based on the two-fluid Euler-Euler approach, where the velocity field of the gas and particles are modeled in analogy to the kinetic gas theory. The proposed numerical model comprises energy equations for all three phases (gas, inert fluidized particles, and liquid fuel), as well as the transport equations of chemical components that are participating in the reactions of combustion and devolatilization. The model equations are solved applying a commercial CFD package, whereby the user submodels were developed for heterogenic fluidized bed combustion of liquid fuels and for interphase drag forces for all three phases. The results of temperature field calculation were compared with the experiments, carried out in-house, on a BFB pilot facility. The numerical experiments, based on the proposed mathematical model, have been used for the purposes of analyzing the impacts of various fuel flow rates, and fluidization numbers, on the combustion efficiency and on the temperature fields in the combustion zone.

Paper presents comparative analysis of residential indoor air pollutant concentration change over future specified time horizon, implementing building physical and thermal retrofit measures, thus creating pollution mitigation scenarios for existing Belgrade and Nis housing stock followed by greenhouse gas emission reduction scenarios up to 2050. Regarding specified mitigation scenarios, the set of typical housing unit models has been generated which define existing housing stock of Belgrade and Nis. Extensive monitoring of physical and thermal parameters as well as detailed socio-technical survey of selected households was performed and used as an initial modeling input. Relationship between environment pollution and building performances was investigated, with respect to indoor-outdoor sources of pollution, thermal and physical properties of the stock samples and occupant's behavior. As a final output, indoor pollutant concentrations for each of the modelled cases was obtained and validated against the available data. This housing modelling framework has been created in order to develop an assessment of present and future exposure and health impact quantity regarding single/multiple scenario interventions introduced to the housing stock. This paper provides each strategy guidelines for taking measures towards achieving the healthier indoor environments.

Primitive controllers used in the early version for HVAC systems, like the on-off (Bang-Bang) controller, are inefficient, inaccurate, unstable, and suffer from high-level mechanical wear. On the other hand, other controllers like PI and cascade controllers, overcome these disadvantages but when an offset response (inaccurate response) occurs, power consumption will increase. In order to acquire better performance in the central air-conditioning system, PIP-cascade control is investigated in this paper and compared to the traditional PI and PID, in simulation of experimental data. The output of the system is predicted through disturbances. Based on the mathematical model of air-conditioning space, the simulations in this paper have found that the PIP-cascade controller has the capability of self-adapting to system changes and results in faster response and better performance.

Air temperature changes on Earth in recent years are the subject of numerous and increasingly interdisciplinary research. In contrast to, conditionally speaking, generally accepted views that these changes are conditioned primarily by anthropogenic activity, more results appear to suggest that it is dominant natural processes about. Whether because of the proven existence of areas in which downtrends are registered or the stagnation of air temperature, as opposed to areas where the increase is determined, in scientific papers, as well as the media, the increasingly present is the use of the term climate changes instead of the global warming. In this paper, we shall try to present arguments for the debate relating to the official view of the Intergovernmental panel on climate change, as well as research indicating the opposite view.

Air temperature changes on Earth in recent years are the subject of numerous and increasingly interdisciplinary research. In contrast to, conditionally speaking, generally accepted views that these changes are conditioned primarily by anthropogenic activity, more results appear to suggest that it is dominant natural processes about. Whether because of the proven existence of areas in which downtrends are registered or the stagnation of air temperature, as opposed to areas where the increase is determined, in scientific papers, as well as the media, the increasingly present is the use of the term climate changes instead of the global warming. In this paper, we shall try to present arguments for the debate relating to the official view of the Intergovernmental panel on climate change, as well as research indicating the opposite view.

In the process of accession to the EU, Republic of Serbia will be obliged to achieve an appropriate share of renewable sources in primary energy consumption in addition to control the emission of carbon dioxide in order to comply with EUs energy policy. In this paper the potential of the production of the so called green electricity from biomass and waste in Republic of Serbia is shown with particular attention to the Electric Power Industry of Serbia, as the largest potential producer of electricity from renewable fuels. Based both on the available total quantity and heating value of non-hazardous solid waste material (municipal and industrial), the calculation of the total available energy potential of waste in Republic of Serbia (by regions) was performed for the state of the 2010th and the projections of waste quantity growth until 2020th. Also, for the same time period, the available amount of waste biomass suitable for (co-)combustion with coal was estimated, as the respective energy potential. The possible energy effects of (co-)combustion in power plants as well as reduced emissions of CO2 with significant financial impact are demonstrated. Actually, this paper demonstrates necessity and techno-economic justification (co-)combustion of renewable fuel with coal in thermal power plants in Serbia.

Paper presents comparative analysis of residential indoor air pollutant concentration change over future specified time horizon, implementing building physical and thermal retrofit measures, thus creating pollution mitigation scenarios for existing Belgrade and Nis housing stock followed by greenhouse gas emission reduction scenarios up to 2050. Regarding specified mitigation scenarios, the set of typical housing unit models has been generated which define existing housing stock of Belgrade and Nis. Extensive monitoring of physical and thermal parameters as well as detailed socio-technical survey of selected households was performed and used as an initial modeling input. Relationship between environment pollution and building performances was investigated, with respect to indoor-outdoor sources of pollution, thermal and physical properties of the stock samples and occupants behavior. As a final output, indoor pollutant concentrations for each of the modelled cases was obtained and validated against the available data. This housing modelling framework has been created in order to develop an assessment of present and future exposure and health impact quantity regarding single/multiple scenario interventions introduced to the housing stock. This paper provides each strategy guidelines for taking measures towards achieving the healthier indoor environments.

Air temperature changes on Earth in recent years are the subject of numerous and increasingly interdisciplinary research. In contrast to, conditionally speaking, generally accepted views that these changes are conditioned primarily by anthropogenic activity, more results appear to suggest that it is dominant natural processes about. Whether because of the proven existence of areas in which downtrends are registered or the stagnation of air temperature, as opposed to areas where the increase is determined, in scientific papers, as well as the media, the increasingly present is the use of the term climate changes instead of the global warming. In this paper, we shall try to present arguments for the debate relating to the official view of the Intergovernmental panel on climate change, as well as research indicating the opposite view.

In the process of accession to the EU, Republic of Serbia will be obliged to achieve an appropriate share of renewable sources in primary energy consumption in addition to control the emission of carbon dioxide in order to comply with EUs energy policy. In this paper the potential of the production of the so called green electricity from biomass and waste in Republic of Serbia is shown with particular attention to the Electric Power Industry of Serbia, as the largest potential producer of electricity from renewable fuels. Based both on the available total quantity and heating value of non-hazardous solid waste material (municipal and industrial), the calculation of the total available energy potential of waste in Republic of Serbia (by regions) was performed for the state of the 2010th and the projections of waste quantity growth until 2020th. Also, for the same time period, the available amount of waste biomass suitable for (co-)combustion with coal was estimated, as the respective energy potential. The possible energy effects of (co-)combustion in power plants as well as reduced emissions of CO2 with significant financial impact are demonstrated. Actually, this paper demonstrates necessity and techno-economic justification (co-)combustion of renewable fuel with coal in thermal power plants in Serbia.

Paper presents comparative analysis of residential indoor air pollutant concentration change over future specified time horizon, implementing building physical and thermal retrofit measures, thus creating pollution mitigation scenarios for existing Belgrade and Nis housing stock followed by greenhouse gas emission reduction scenarios up to 2050. Regarding specified mitigation scenarios, the set of typical housing unit models has been generated which define existing housing stock of Belgrade and Nis. Extensive monitoring of physical and thermal parameters as well as detailed socio-technical survey of selected households was performed and used as an initial modeling input. Relationship between environment pollution and building performances was investigated, with respect to indoor-outdoor sources of pollution, thermal and physical properties of the stock samples and occupants behavior. As a final output, indoor pollutant concentrations for each of the modelled cases was obtained and validated against the available data. This housing modelling framework has been created in order to develop an assessment of present and future exposure and health impact quantity regarding single/multiple scenario interventions introduced to the housing stock. This paper provides each strategy guidelines for taking measures towards achieving the healthier indoor environments.

Air temperature changes on Earth in recent years are the subject of numerous and increasingly interdisciplinary research. In contrast to, conditionally speaking, generally accepted views that these changes are conditioned primarily by anthropogenic activity, more results appear to suggest that it is dominant natural processes about. Whether because of the proven existence of areas in which downtrends are registered or the stagnation of air temperature, as opposed to areas where the increase is determined, in scientific papers, as well as the media, the increasingly present is the use of the term climate changes instead of the global warming. In this paper, we shall try to present arguments for the debate relating to the official view of the Intergovernmental panel on climate change, as well as research indicating the opposite view.

The paper deals with the development of mathematical models for detailed simulation of lateral jet penetration into the fluidized bed, primarily from the aspect of feeding of gaseous and liquid fuels into fluidized bed furnaces. For that purpose a series of comparisons has been performed between the results of in-house developed procedure -fluid-porous medium numerical simulation of gaseous jet penetration into the fluidized bed, Fluent's two-fluid Euler-Euler fluidized bed simulation model, and experimental results (from the literature) of gaseous jet penetration into the 2-D fluidized bed. The calculation results, using both models, and experimental data are in good agreement. The developed simulation procedures of jet penetration into the fluidized bed are applied to the analysis of the effects, which are registered during the experiments on a fluidized pilot furnace with feeding of liquid waste fuels into the bed, and brief description of the experiments is also presented in the paper. Registered effect suggests that the water in the fuel improved mixing of fuel and oxidizer in the fluidized bed furnace, by increasing jet penetration into the fluidized bed due to sudden evaporation of water at the entry into the furnace. In order to clarify this effect, numerical simulations of jet penetration into the fluidized bed with three-phase systems: gas (fuel, oxidizer, and water vapour), bed particles and water, have been carried out.

The paper deals with the development of mathematical models for detailed simulation of lateral jet penetration into the fluidized bed, primarily from the aspect of feeding of gaseous and liquid fuels into fluidized bed furnaces. For that purpose a series of comparisons has been performed between the results of in-house developed procedure fluid-porous medium numerical simulation of gaseous jet penetration into the fluidized bed, Fluents two-fluid Euler-Euler fluidized bed simulation model, and experimental results (from the literature) of gaseous jet penetration into the 2-D fluidized bed. The calculation results, using both models, and experimental data are in good agreement. The developed simulation procedures of jet penetration into the fluidized bed are applied to the analysis of the effects, which are registered during the experiments on a fluidized pilot furnace with feeding of liquid waste fuels into the bed, and brief description of the experiments is also presented in the paper. Registered effect suggests that the water in the fuel improved mixing of fuel and oxidizer in the fluidized bed furnace, by increasing jet penetration into the fluidized bed due to sudden evaporation of water at the entry into the furnace. In order to clarify this effect, numerical simulations of jet penetration into the fluidized bed with three-phase systems: gas (fuel, oxidizer, and water vapour), bed particles and water, have been carried out.

The paper deals with the development of mathematical models for detailed simulation of lateral jet penetration into the fluidized bed, primarily from the aspect of feeding of gaseous and liquid fuels into fluidized bed furnaces. For that purpose a series of comparisons has been performed between the results of in-house developed procedure fluid-porous medium numerical simulation of gaseous jet penetration into the fluidized bed, Fluents two-fluid Euler-Euler fluidized bed simulation model, and experimental results (from the literature) of gaseous jet penetration into the 2-D fluidized bed. The calculation results, using both models, and experimental data are in good agreement. The developed simulation procedures of jet penetration into the fluidized bed are applied to the analysis of the effects, which are registered during the experiments on a fluidized pilot furnace with feeding of liquid waste fuels into the bed, and brief description of the experiments is also presented in the paper. Registered effect suggests that the water in the fuel improved mixing of fuel and oxidizer in the fluidized bed furnace, by increasing jet penetration into the fluidized bed due to sudden evaporation of water at the entry into the furnace. In order to clarify this effect, numerical simulations of jet penetration into the fluidized bed with three-phase systems: gas (fuel, oxidizer, and water vapour), bed particles and water, have been carried out.

This paper includes comparative analysis of the environmental, energetic, and financial costs of different bus propulsion, possibly applied on the public transport in the city of Belgrade. It considers the modern diesel bus, the trolleybus, the natural gas bus with the spark ignition engine, the electric bus using LiFePO4 battery, and the electric bus with ultra-capacitor. The results are presented according to the real data and the real electro-energetic situation in Serbia, with the dominantly used lignite coal as primary fuel. This model gives the exact exhaust emission of electric vehicles at the thermal power plant, enables its comparison to the internal combustion engine vehicles. The result in analysis shows that the natural gas bus is the most cost efficient in economical way with overall exploitation price of $87 per 100 km. The trolleybus is more economical then the natural gas powered bus only at high departures rate, higher than 230 per workday.

This paper, dealing with the problems of mathematical description of the tunnel fire development process with the use of experimental data, outlines the procedure of correction of the existing and obtaining of an improved CFD model package. The improved CFD model was developed on the basis of detailed analysis and comparison of experimental and numerical results, through consideration of the physical structure of all processes affecting combustion. During the analysis it was noticed that the existing CFD model in the part covering combustion based on the so-called steady laminar flamelet model, treats the combustion process almost as a direct correlation between the processes of mixing gasses and heat release rate. This potential deficiency has been overcome by correction of the model in the section defining boundary condition for the burning surface and by establishing a direct correlation between the measured value of the fuel mass change rate and the amount of heat released from burning surface. In this way a modification of complex stoichiometric combustion processes was avoided, while providing the model that better describes and predicts the course of events in this type of complex, anisotropic and turbulent flow of gases in the tunnel.

Expression "Development conditions and perspectives" became important for numerous analyses in various industrial and social areas. Several strategic documents and studies in last two decades analysed projects with topics on perspectives of future development in Serbia. Various tools are used for development of such documents, based on recent scientific and numerical solutions, thus providing reliable assessment for strategic decision making. Almost all analyses tried to implement the theories and practical experiences through the prism of "sustainable development", which included establishment of most important sitstainability parameters. Analysis and ranking presented in this paper considered the potential of the Stavalj coal deposit, near city of Sjenica in Serbia, and feasibility of construction project of new mine and thermal power plant. Basis for analysis was a hybrid assessment model which takes into account principles of sustainable development. The model incorporates quantified SWOT analysis, which applies to active underground mines in Serbia. Special attention was given to the parameters describing potential for development.

Flow through packed beds of spheres is a complex phenomenon and it has been extensively studied. Although, there is many different correlations there is still no reliable universal equation for prediction of pressure drop. The paper presents the results of experimental research of pressure drop in packed bed of monosized spheres of three different diameters, 8, 11, and 13 mm set within cylindrical vessel of diameter d(k) = 74 mm, and two different heights of packed bed, h(s) = 300 and 400 mm. It has been proposed modification of widely used Ergun's equation in the form of f(p) = [150 + 1.3(Re-p/(1 - epsilon))](1 - epsilon)(2)/(epsilon Re-3(p)) and new correlation f(p) = 1/[(27.4 - 25700d(h))/Re-p + 0.545 + 6.85d(h)] for pressure drop calculation in simple and convenient form for hand and computer calculations. For total number of 362 experimental runs the correlation ratio of the modified Ergun's relation was CR = 99.3%, and standard deviation SD = 12.2%, while novel relation has CR = 93.7% and SD = 5.4%.

High-temperature thermal process is a commercial way of regeneration of spent granular activated carbon. The paper presents results of thermal analysis conducted in order to examine high-temperature regeneration of spent activated carbon, produced from coconut shells, previously used in drinking water treatment. Results of performed thermogravimetric analysis, derivative thermogravimetric analysis, and differential thermal analysis, enabled a number of hypotheses to be made about different phases of activated carbon regeneration, values of characteristic parameters during particular process phases, as well as catalytic impact of inorganic materials on development of regeneration process. Samples of activated carbon were heated up to 1000 degrees C in thermogravimetric analyser while maintaining adequate oxidizing or reducing conditions. Based on diagrams of thermal analysis for samples of spent activated carbon, temperature intervals of the first intense mass change phase (180-215 degrees C), maximum of exothermic processes (400-450 degrees C), beginning of the second intense mass change phase (635-700 degrees C), and maximum endothermic processes (800-815 degrees C) were determined. Analysing and comparing the diagrams of thermal analysis for new, previously regenerated and spent activated carbon, hypothesis about physical and chemical transformations of organic and inorganic adsorbate in spent activated carbon are given. Transformation of an organic adsorbate in the pores of activated carbon, results in loss of mass and an exothermic reaction with oxygen in the vapour phase. The reactions of inorganic adsorbate also result the loss of mass of activated carbon during its heating and endothermic reactions of their degradation at high temperatures.

Results of experimental investigations of the turbulent swirl flow in three straight conical diffusers with various diffuser total angles are presented in this paper. All three diffusers have the inlet diameter 0.4 m and total divergence angles 8.6 degrees, 10.5 degrees, and 12.6 degrees. The incompressible swirl flow field is generated by the axial fan impeller, and for each diffuser several regimes were achieved by changing rotation number. Original classical probes were used for measurements. The distributions of the average main swirl flow characteristics along the diffuser are shown. Distributions of the inlet Boussinesq number, outlet Coriolis coefficient, ratio of the swirl and completely axial flow loss coefficients at conical diffuser on the inlet swirl flow parameter are also presented.

This paper presents modcation of the existing guided missile which was done by replacing the existing front part with the new five, while the rear part of the missile with rocket motor and missile thrust vector control system remains the same. The shape of all improved front parts is completely different from the original one. Modification was performed based on required aerodynamic coefficients for the existing guided missile. The preliminary aerodynamic configurations of the improved missile front parts were designed based on theoretical and computational fluid dynamics simulations. All aerodynamic configurations were tested in the T-35 wind tunnel at the Military Technical Institute in order to determine the final geometry of the new front parts. The 3-D Reynolds averaged Navier-Stokes numerical simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. Experimental results of the axial force, normal force, and pitching moment coefficients are presented. The computational results of the aerodynamic loads of a guided missile model are also given, and agreed well with.

This paper presents results of our own velocity field measurements in a straight pipe swirl flow. These studies were conducted using an originally designed hot wire probe. Due to the specially tailored shape of the probe, it was possible to get four measurement points in the viscous sublayer. The time-averaged velocity field and the statistical moments of the second and third order are calculated based on the measured velocity components. Mathematical and physical interpretations of statistical characteristics and structures of turbulent swirl flow in the time domain are presented. On the basis of these results, deeper insight into turbulent transport processes can be obtained, as well as useful conclusions necessary for turbulent swirl flows modeling.

This paper includes comparative analysis of the environmental, energetic, and financial costs of different bus propulsion, possibly applied on the public transport in the city of Belgrade. It considers the modern diesel bus, the trolleybus, the natural gas bus with the spark ignition engine, the electric bus using LiFePO4 battery, and the electric bus with ultra-capacitor. The results are presented according to the real data and the real electro-energetic situation in Serbia, with the dominantly used lignite coal as primary fuel. This model gives the exact exhaust emission of electric vehicles at the thermal power plant, enables its comparison to the internal combustion engine vehicles. The result in analysis shows that the natural gas bus is the most cost efficient in economical way with overall exploitation price of $87 per 100 km. The trolleybus is more economical then the natural gas powered bus only at high departures rate, higher than 230 per workday.

A thermal buckling analysis of functionally graded thick rectangular plates according to von Karman non-linear theory is presented. The material properties of the functionally graded plate, except for the Poisson's ratio, were assumed to be graded in the thickness direction, according to a power-law distribution, in terms of the volume fractions of the metal and ceramic constituents. Formulations of equilibrium and stability equations are derived using the high order shear deformation theory based on different types of shape functions. Analytical method for determination of the critical buckling temperature for uniform increase of temperature, linear and non-linear change of temperature across thickness of a plate is developed. Numerical results were obtained in MATLAB software using combinations of symbolic and numeric values. The paper presents comparative results of critical buckling temperature for different types of shape functions. The accuracy of the formulation presented is verified by comparing to results available from the literature.

This paper presents the techno-economic optimization of batch plant for production of rectified alcohol based on the concentration of ethanol in residue. The aim of the analysis was to determine the extent to which it is economically profitable to exhaust the residual liquid in boiler. The "profit production" criterion is used for calculations.

This paper pays attention to develop a variable-order fractal derivative model for anomalous diffusion. Previous investigations have indicated that the medium structure, fractal dimension or porosity may change with time or space during solute transport processes, results in time or spatial dependent anomalous diffusion phenomena. Hereby, this study makes an attempt to introduce a variable-order fractal derivative diffusion model, in which the index of fractal derivative depends on temporal moment or spatial position, to characterize the previous mentioned anomalous diffusion (or transport) processes. Compared with other models, the main advantages in description and the physical explanation of new model are explored by numerical simulation. Further discussions on the dissimilitude such as computational efficiency, diffusion behavior, and heavy tail phenomena of the new model, and variable-order fractional derivative model are also offered.

Computational fluid dynamics computations for two hypersonic flow cases using the commercial ANSYS FLUENT 16.2 CFD software were done. In this paper, an internal and external hypersonic flow cases were considered and analysis of the hypersonic flow using different turbulence viscosity models available in ANSYS FLUENT 16.2 as well as the laminar viscosity model were done. The obtained results were after compared and commented upon.

The paper presents high-speed stereo particle image velocimetry investigation of the NASA Common Research Model wing tip vortex. A three-percent scaled semi span model, without nacelle and pylon, was tested in the 32- by 48-inch In draft tunnel, at the Fluid Mechanics Laboratory at the NASA Ames Research Center. Turbulence investigation of the wing tip vortex is presented. Measurements of the wing-tip vortex were performed in a vertical cross-stream plane three tip-chords downstream of the wing tip trailing edge with a 2 kHz sampling rate. Experimental data are analyzed in the invariant anisotropy maps for three various angles of attack (0 degrees, 2 degrees, and 4 degrees) and the same speed generated in the tunnel (V-infinity = 50 m/s). This corresponds to a chord Reynolds number 2.68.10(5), where the chord length of 3" is considered the characteristic length. The region of interest was x = 220 mm and y = 90 mm. The 20 000 particle image velocimetry samples were acquired at each condition. Velocity fields and turbulence statistics are given for all cases, as well as turbulence structure in the light of the invariant theory. Prediction of the wing tip vortices is still a challenge for the computational fluid dynamics codes due to significant pressure and velocity gradients.

Experimental investigation of the free turbulent swirl jet behind the axial fan, by use of the three-component laser Doppler anemometry is presented in this paper. Axial fan generates Rankine swirl. Measurements have been performed in five vertical measuring sections downstream for one rotation number 1500 rpm. Time averaged velocity components and their profile transformation downstream were investigated. Statistical moments of the second, third and fourth order have been calculated and presented. The highest turbulence levels are reached in the central zone, more precisely - shear layer zone and in the injection zone. Skewness and flatness factors differ from normal Gaussian distributions. Turbulence swirl flow anisotropy is investigated by applying invariant maps. Most of the obtained results are positioned in the region of the three-component isotropic turbulence and axisymmetric expansion.

The work presented in this paper is dealing with numerical simulation of energy separation mechanism and flow phenomena within a Ranque-Hilsch vortex tube. Simulation of turbulent, compressible, highly swirling flow inside vortex tube is performed using RANS approach, with Favre averaged conservation equations. For turbulence closure, k-epsilon and k-omega shear-stress transport models are used It is assumed that the mean flow is axisymmetric, so the 2-D computational domain is used. Computations were performed using open-source CFD software Open FOAM All compressible solvers available within OpenFOAM were tested, and it was found that most of the solvers cannot predict energy separation. Code of two chosen solvers, which proved as the most robust, is modified in terms of mean energy equation implementation. Newly created solvers predict physically accepted behavior in vortex tube, with good agreement with experimental results. Comparison between performances of solvers is also presented

The paper presents a novel method for hypolimnetic oxygenation by electrolysis of water. The performance of the method is investigated by the laboratory and the field experiment. The laboratory experiment is conducted in a 90 L vessel, while the field experiment is conducted at the lake Biwa in Japan. In order to provide a better insight into involved processes, a numerical model for simulation of bubble flow is developed with consideration of gas compressibility and oxygen dissolution. The model simultaneously solves 3-D volume averaged two-fluid governing equations. Developed model is firstly verified by simulation of bubble flow experiments, reported in the literature, where good qualitative agreement between measured and simulated results is observed In the second part, the model is applied for simulation of conducted water electrolysis experiments. The model reproduced the observed oxygen concentration dynamics reasonably well.

Oxy-fuel coal combustion, together with carbon capture and storage or utilization, is a set of technologies allowing to burn coal without emitting globe warming CO2. As it is expected that oxy-fuel combustion may be used for a retrofit of existing boilers, development of a novel oxy-burners is very important step. It is expected that these burners will be able to sustain stable flame in oxy-fuel conditions, but also, for start-up and emergency reasons, in conventional, air conditions. The most cost effective way of achieving dual-mode boilers is to introduce dual-mode burners. Numerical simulations allow investigation of new designs and technologies at a relatively low cost, but for the results to be trustworthy they need to be validated This paper proposes a workflow for design, modeling, and validation of dual-mode burners by combining experimental investigation and numerical simulations. Experiments are performed with semi-industrial scale burners in 0.5 MW, test facility for flame investigation. Novel CFD model based on ANSYS FLUENT solver, with special consideration of coal combustion process, especially regarding devolatilization, ignition, gaseous and surface reactions, NOx formation, and radiation was suggested The main model feature is its ability to simulate pulverized coal combustion under different combusting atmospheres, and thus is suitable for both air and oxy-fuel combustion simulations. Using the proposed methodology two designs of pulverized coal burners have been investigated both experimentally and numerically giving consistent results. The improved burner design proved to be a more flexible device, achieving stable ignition and combustion during both combustion regimes: conventional in air and oxy-fuel in a mixture of O-2 and CO2 (representing dry recycledflue gas with high CO2 content). The proposed framework is expected to be of use for further improvement of multi-mode pulverized fuel swirl burners but can be also used for independent designs

Transient hot wire method is considered a reliable and precise technique for measuring the thermal conductivity of liquids. The present paper describes a new transient hot wire experimental set-up and its initial testing. The new apparatus was tested by performing thermal conductivity measurements on substances whose reference thermophysical properties data existed in literature, namely on pure toluene and double distilled deionized water. The values of thermal conductivity measured in the temperature range 25 to 45 degrees C deviated +2.2% to +3% from the literature data, while the expanded measurement uncertainty was estimated to be +/- 4%.

Transient hot wire method is considered a reliable and precise technique for measuring the thermal conductivity of liquids. The present paper describes a new transient hot wire experimental set-up and its initial testing. The new apparatus was tested by performing thermal conductivity measurements on substances whose reference thermophysical properties data existed in literature, namely on pure toluene and double distilled deionized water. The values of thermal conductivity measured in the temperature range 25 to 45 degrees C deviated +2.2% to +3% from the literature data, while the expanded measurement uncertainty was estimated to be +/- 4%.

Transient hot wire method is considered a reliable and precise technique for measuring the thermal conductivity of liquids. The present paper describes a new transient hot wire experimental set-up and its initial testing. The new apparatus was tested by performing thermal conductivity measurements on substances whose reference thermophysical properties data existed in literature, namely on pure toluene and double distilled deionized water. The values of thermal conductivity measured in the temperature range 25 to 45 degrees C deviated +2.2% to +3% from the literature data, while the expanded measurement uncertainty was estimated to be +/- 4%.