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The majority of studies dealing with the correlation between human body exergy consumption and thermal comfort, use adopted, constant values of metabolic rate for appropriate activity level. Taking into account correlations between metabolic rate and the occupant’s exhaled CO2 volumetric flow rate, this study proposes a novel method for the calculation of metabolic rate using measured CO2 concentration in the indoor air. Using measured values of the air and radiant temperature, relative humidity and air velocity, and calculated values of metabolic rate, the human body exergy consumption rate and corresponding Predicted Mean Vote (PMV) are calculated. Moreover, a novel polynomial relation between them is proposed. Results show that metabolic rate values vary in the range of 0.97 to 1.54 met which leads to significantly wider range of PMV and human body exergy consumption rate comparing to the assumed value of 1.2 met for sedentary school activity. According to the obtained relation, the minimal value of the human body exergy consumption rate occurs for PMV = - 0.02. Results of this study imply that treating CO2 concentration as variable does have an impact on the thermal comfort assessment, providing enhanced correlations between thermal comfort and human body exergy consumption rate.

М60 М63

Regarding to the structure of final energy consumption in buildings and National Action Plans, the paper gives a short overview of energy consumption in buildings in Serbia, showing that the greatest potential for achieving savings lies in the implementation of measures which improve energy efficiency. Considering that over 60% of energy requirements for buildings is related to thermal energy, particular attention should be paid to the centralized heating systems, both during the design of a new system, and in the reconstruction of the existing one. Further discussed are the heat sources for the heating systems. The seasonal heat load duration curve for winter conditions in accordance to the Typical Meteorological Year for Belgrade is constructed and displayed. The analysis of the conventional system with a fossil fuel source, as well as the analysis of a hybrid heat source are conducted. The savings achieved in the primary energy, heating bills and CO emission reduction, which are attained by the use of a hybrid system, are shown in 2 comparison with the conventional systems. Collecting data on investment costs, as well as the prices of energy and fuels in Serbian market, enabled calculation of the payback period when replacing the conventional system by the new hybrid one.

Green roof systems have become an important part in creating sustainable cities. They can provide a wide range of economic, environmental, and social benefits. The goal of this research was to quantify the thermal performance improvements from a green roof with mineral wool substrate installed on a school building in a humid subtropical climate. In-situ measurements during a summer period included heat fluxes through the green and reference roof, vertical temperature profile through both roofs, the local air temperature above roofs, and local meteorological parameters. Furthermore, the summer thermal performance of green and reference roof and the green roof cooling effect were evaluated concerning meteorological parameters using the Pearson correlation analysis. The results indicate that the green roof layers have improved thermal performance of the roof with respect to reduced conductive heat flow by 57% and delayed heat transfer. The maximum and averaged reference roof to green roof outdoor surface temperature difference was 27.5 °C and 5.5 °C, respectively. It was found that ambient temperature and relative humidity have a dominant role on the thermal performance of the green and reference roof, while solar radiation and ambient temperature present the key meteorological determinants of the green roof cooling effect.

М30 М34

М30 М34

The systematically varying properties and generally coherent and predictable behavior of rare earth elements (REE) make them potential tracers for studying water/rock interaction and weathering processes. In this work, a compilation and analysis of REE data in mineral and thermal waters were performed, focusing on their content and distributions in different hydrogeological systems, to quantify the natural REE variability and to discuss the controlling factors of REE concentrations. Quantitative challenges presented by multiply censored data were addressed with nonparametric and multivariate statistical methods. Considering a regional character of the research the application of Q and R mode Hierarchical Cluster Analysis with spatial analysis was an important approach for meaningful interpretation of large data set. An efficient approach to analyze differences between obtained HCA groups (clusters) was using a plot of reference-normalized concentrations. The results showed that REE data along with anomalies of Ce and Eu and inter-element ratios were good indicators of the aquifer lithology (hydrogeological systems formed in granitoid and volcanic rocks of various age, two main types of hydrogeological basins, and carbonate aquifers). The important mechanisms controlling REE migration in water were hydrochemical conditions in aquifers. The significance of the applied statistical analyses was represented by defining specific hydrochemical fingerprints of identified hydrogeological systems with distinct geochemical characteristics where REE showed the necessity of understanding of complex geological and hydrogeological settings, geodynamic evolution, and hydrogeochemical processes in fluid flow systems.

The objective of this paper was to determine background values (BV) and anomalous values (AV) of U and Th in groundwater and to establish hydrogeochemical conditions which lead to the elevated concentrations of these elements in groundwater. The methodology included planning and collecting of water samples, laboratory work, and assessment of BV and AV concentrations in accordance with the dataset distribution, based on consideration of hydrogeochemical conditions in the hydrogeological system. Groundwater sampling included 144 occurrences of mineral and thermal water from Serbian territory, belonging to different hydrogeological systems. Field parameters were measured for temperature (T), pH, electrical conductivity (EC), oxidation–reduction potential (ORP), dissolved oxygen (DO), and carbon dioxide (CO2). Standard laboratory measurements were applied for the determination of major chemical components (Ca, Mg, Na, K, Cl, HCO3, and SO4) and U and Th concentrations were measured by ICP-MS. The first step for obtaining U and Th threshold values was based on non-parametric statistical analysis on the data sets. Further analysis of threshold values enabled establishing hydrogeochemical conditions influencing elevated concentrations of U and Th and setting up the logistic regression (LR) model. Differences in the hydrochemical properties of U and Th can be observed based on predictor variables from LR models. Physico-chemical parameters Eh and pH, groundwater type, and geochemical environment (cretaceous igneous rocks) were significant predictors for elevated uranium concentrations, while significant predictors in the thorium LR model were the pH value, the concentration of SO4 in the solution, and the water-bearing rocks (tertiary igneous rocks).

М60 М64

М30 М34

This paper presents a new laboratory set-up for the air-conditioning operation analysis in the Laboratory for Automatic Control at the Faculty of Mechanical Engineering, University of Belgrade. The new HVAC laboratory is designed to investigate different complex HVAC system working regimes and to provide desired space comfort. The emphasis is specially given to an impact on energy consumption. The laboratory set-up is designed to operate in the complex, dynamic regimes, when indoor environment parameters are intensively changed, together with a change of outdoor conditions. In order to minimize energy consumption, a new software and various automatic control algorithms are designed for automatic control of the air handlig unit.

М30 М34

М60 М64

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 city of 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 predicted mean vote and predicted percentage dissatisfied 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 predicted mean vote, 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. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. 33047 and Grant no. III 42008]

The paper deals with a comprehensive, three-dimensional numerical CFD analysis of temperature fields in Trombe wall and in the adjacent room for several days of a typical meteorological year (TMY) for a moderate continental climate. Construction of the Trombe wall is optimized, using different types of glassing on the outside of the wall. For summer day, the glass is considered to be covered with PV stripes during the daylight in order to prevent overheating. The central concrete core of the wall is covered with a layer of dark paint, on the outside, to improve absorptivity of the wall. The Trombe wall is oriented on south side of the house, and designed with openings with flaps in concrete core. Those openings are simulated in opened and closed positions. The U-values of the house envelope are considered according to passive house standards. Temperature fields in concrete core and in the room with Trombe wall are simulated, as well as velocity fields. According to these results, analysis of energy savings potential is performed.

М30 М34

This paper analyses the influence of time-predicted night ventilation applied during the summer season on the total energy consumption of airconditioning system. Analysis has been made on the basis of a computer program for dynamic simulation of air-conditioned rooms thermal behavior. The program was developed at the Department for Thermal Engineering at the Faculty of Mechanical Engineering, University of Belgrade. Air-conditioning operating modes without and with application of night ventilation, and different periods of night ventilation are analyzed. Cooling loads, fan energy consumption and overall energy consumption for summer conditions for Belgrade for the whole cooling season are given. The obtained results were compared, and hereupon a review is given of the energy savings for the whole cooling season.

Magnesium is chemical element commonly found in the environment and the main constituent of many types of minerals and rocks. This element is also essential to man. Owing to its abundance in nature, magnesium is present in all water resources and generally occur as the dominant cation, with calcium, in those that feature low TDS levels, whose origin is associated with large formations of sedimentary rocks (limestones, dolomites), and to a lesser extent with the degradation of silicate minerals that contain Mg. Magnesium concentrations in groundwater of Serbia vary over a wide range and their distribution is not uniform, but certain laws of nature do apply. The variation in the concentrations of this ion depends on the considered hydrogeological province, while within a single province it is a consequence of Serbia’s highly complex geology. The best examples are the Carpatho-Balkanides, with predominant karstified rock formations, and the Vardar Zone where ophiolites prevail but the makeup is much more complex than that of the Carpatho-Balkanides. [Projekat Ministarstva nauke Republike Srbije, br. 43004]

Multivariate statistical analyses are used for reducing large datasets to a smaller number of variables, which explain main hydrogeochemical processes that control water geochemistry. Factor analysis (FA) allows discovering intercorrelations inside the data matrix and grouping of similar variables, i.e. chemical parameters. In this way new variables are extracted, which are called factors, and each factor is explained by some hydrogeochemical process. Applying FA to a dataset that consists of 15 chemical parameters measured on 40 groundwater samples from Serbia, four factors were extracted, which explain 73.9% of total variance in the analyzed dataset. Interpretation of obtained factors indicated several hydrogeochemical processes: the impact of sea water intrusions and volatiles in previous geological periods, solutes diffusion from the marine clay, cation exchange and dissolution of carbonate and silicate minerals. [Projekat Ministarstva nauke Republike Srbije, br. 43004]

Twenty-one bottled mineral and spring waters from Serbia were analyzed for 16 inorganic chemical parameters, including lanthanides and yttrium which belong to the group of so-called rare earth elements (REE). REE concentrations in the bottled water samples varied over a broad range, from 5.39 to 1585.82 ng/L. Total concentrations in the bottled water samples were calculated taking into account the classification of lanthanides into heavy (HREE) and light (LREE), with yttrium added to the HREE group. The LREE concentrations ranged from 3.62 to 1449.63 ng/L, while those of the HREE were from 0 to 136.19 ng/L. Distinct REE signatures were observed in waters that drained specific rocks. The REE patterns in groundwater from granitic and related rocks showed LREE and HREE enrichment, while groundwater with mafic rock influence exhibited slightly LREE enrichment. Several bottled water samples featured naturally-occurring carbon dioxide, whose solutional capacity contributed to the highest REE concentrations in the analyzed samples. High REE concentrations are also a result of sudden changes in oxidation-reduction conditions, which particularly affect La, Ce and Eu. Aquifers developed in granitic and related rocks (methamorphic and sedimentary rocks) constitute favorable environments for HREE in groundwater, corroborated by the occurrence of HREE in bottled water samples. The bottled water samples largely exhibited a negative cerium anomaly and nearly all the samples showed a positive europium anomaly.

М60 М63

2/11 M20 М23

A new approach using hydrochemical characterization of mineral water in Serbia was applied in this paper. After field research and groundwater sampling, laboratory measurements were conducted. Trace and ultratrace elements in 174 samples of mineral water were analyzed using HR ICP–MS and methods to determine gross alpha/beta activities were applied. Hierarchical cluster analysis (HCA) was used on selected variables: major ions (Ca, Mg, Na, Cl, HCO3, SO4), Si, temperature, electrical conductivity (EC), pH and Eh. Results showed that variability of chemical characteristics, and diverse mineral and thermal water types were grouped into six clusters. Geochemical conditions of each cluster were considered in detail in terms of basic hydrochemical parameters, geological characteristics, and the contents of particular elements. There were certain regularities among the separated groups. Water differed in temperatures, dissolved mineral substances, pH, Eh values and gas content, which indicated different hydrogeological conditions. Variations among clusters in natural radioactivity, the content of essential elements and rare earth elements (REE) are also discussed.

In this paper, presented is the state of the art of Energy Efficiency (EE) of residential buildings in Serbia. Special attention is paid to energy efficiency in already existing buildings. The average energy consumption in residential buildings in Serbia is over 150 kWh/m2 per year, while in developed European countries it is about 50 kWh/m2 per year. In this paper examined is the contribution of ventilation losses, through the windows of low quality, regardless whether they are poorly made, or made from bad materials, or with no adequate glass. Besides ventilation losses, which are of major importance in our buildings, special attention is paid to transmission losses, which are consequence of the quality and energy efficiency of the facade. All of the above statements are proved by measurements obtained on a representative building of the Block 34 in New Belgrade, built in the eighties of the last century. In addition to measurements performed the calculation of energy consumption for heating during winter has been made. The results of two different methods of calculation of energy consumption for heating are compared with the values obtained by measuring.

For the present study, 172 groundwater samples (collected from wells and natural springs in Serbia) were analyzed for different chemical parameters including uranium. For each groundwater sample, information was compiled about the basic parameters of its chemical composition. Most of the samples were found to be of the Na – HCO3 and Ca, Mg − HCO3 water types, while only a few were classified as the Ca, Mg – SO4 or Na − Cl type. HR–ICP–MS is an analytical technique used for uranium determinations. The measured concentrations of uranium were in the range from 0.0005 μg/L to 25.34 μg/L.

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М60 М63

6 21 M20 М23

М30 М33