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Korišćenje energija iz obnovljivih izvora sve više zaokupira pažnju istraživača. Potreba za redukcijom potrošnje električne enegije u oblasti klimatizacije i čuvanja hrane upućuje na sisteme u kojima se, za postizanje rashladnog efekta, koriste solarna energija ili otpadna toplota. Pored apsorpcionih i ejektorskih uređaja, značajno mesto u ovoj oblasti sve više zauzimaju i adsorpcioni rashladni sistemi. I pored toga što solarno adsorpciono hlađenje predstavlja jednu od najnovijih tehnologija solarnog hlađenja, ona u sadašnje vreme uveliko prevazilazi faze pilot ili demonstracionih instalacija. Proširenje tržišta, klimatske promene i povećana ekološka svest, pokazuju značajan potencijal za razvoj upravo ovkavih sistema.

People's awareness of the importance of energy consumption in the industrial sector is growing due to the fact that the industrial sector is responsible for about third of the world's energy supply. The main challenge of each energy sector is reflected in increasing efficiency in each of its parts, which is directly related to the positive effects on human health, the environment and the economy of a country. Energy efficiency is often referred to as the "fifth fuel" (after gas, coal, nuclear and renewable energy) and can play a key role in meeting global power demand and mobility. This paper focuses on possible approaches and measures that lead to the reduction of energy consumption and the improvement of energy efficiency of various sectors in industry. In addition to improving energy efficiency in energy processes and the use of energy efficient technologies to reduce energy consumption in the industrial sector, it is necessary to provide energy efficient strategies that improve the functioning of the industrial sector, especially for developing countries.

The paper deals with an analysis of existing thermal comfort models based on exergy approach and the impact of models’ input parameters to the calculation results. The aim of this paper is to present the results of the application of five different thermal comfort models based on the exergy analysis, to compare them, and to determine if they coincide with the results obtained by using Fanger’s model. While models that are the most commonly used to evaluate and predict thermal comfort conditions are based on the first law of thermodynamics, a handful of authors used both the first and the second law of thermodynamics in order to develop new thermal comfort models. Even though the optimal comfort conditions according to these models may not differ by large margin from the optimal thermal comfort conditions according to Fanger’s model, it is concluded that justification of using models based on the exergy analysis to evaluate thermal comfort is very dependent on the input parameters, which should all be taken into consideration separately.

The use of carbon dioxide (CO2) refrigeration systems is increasingly present in modern supermarkets. Compared to conventional systems with freons, these systems use a natural and environmentally friendly refrigerant, but their energy efficiency is lower. However, with the advent of new technologies and better understanding of carbon dioxide, space has been created for system improvement and the introduction of new technical solutions. Also, one of the useful methods for improving the operation of the transcritical CO2 system is the determination of the optimum high side pressure in the gas cooler. In this paper, two transcritical CO2 systems (1st generation) are presented, which represent a potential technical solution for the system that will be carried out in the Laboratory for Thermal Science at the Faculty of Mechanical Engineering in Belgrade. In order to maintain the maximum coefficient of performance (COP) with optimum high side pressure, a thermodynamic analysis was carried out for one selected system. In addition to the influence of the ambient air temperature, the possible affecting parameters on COP and optimum high side pressure was also considered. Finally, a proper control equation is given.

Residential sector is considered one of the largest consumers of primary energy in the world. The main part of total energy consumption in buildings refers to heating. The study presents a thermodynamic sustainability assessment of different energy sources for residential building heating. The paper presents universal methodology, which can be applied to energy and exergy analysis for all types of buildings. Various options of energy sources were studied, namely: coal, natural gas, electricity, district heating, air-water heat pump, biomass and district heating with a cogeneration. Energy and exergy analyses were conducted and appropriate efficiencies were determined. The calculation of an environmental impact factor and exergetic sustainability index for all types of considered energy sources was performed. The results showed that exergy efficiency was very low in all analyzed cases except for biomass, which leads to poor thermodynamic compatibility of energy quality from the supplied side and the energy used for building heating. It was shown that the highest exergy efficiency was in the case of biomass utilization (about 29%), due to the energy used from renewable energy sources. The minimum environmental impact factor (2.48) and maximum exergetic sustainability index (0.403) were found for the case of biomass utilization.

У раду је приказан развијени софтверски систем за прорачун топлотних шема постројења са парним турбинама и припадајућим моделима за одређивање радних параметара појединачних компоненти оваквих постројења. У току развоја оваквог система анализиране су различите методе доступне у литератури. На основу развијених модела и целокупне методологије прорачуна, написан је рачунарски програм са графичким интерфејсом, широког спектра примене. Програм је конципиран и развијен на начин да поседује флексибилност у погледу конфигурисања прорачунаване топлотне шеме постројења, те се може примењивати за различите типове турбопостројења, с тим да се у оквиру топлотне шеме различите компоненте се могу неограничено додавати. За сваку од компоненти развијен је одговарајући математички модел који омогућава процену њених геометријских карактеристика (дизајн мод), као и развијени модел који омогућава симулацију њеног рада при промени радних услова (анализа мод). Радни услови постројења могу бити унапред задати или су резултат мерења у току рада реалног погона на основу аквизиције и обраде података. Програм је робустан и захтева кратко време за спровођење прорачуна. Имплементирани модели и целокупна метода прорачуна су вишеструко валидирани поређењем са резултатима термотехничких пријемних и погонских испитивања парних турбина и турбопостројења спроведених од стране Лабораторије за топлотне турбомашине и термоенергетска постројења Машинског факултета. Тиме је постигнут висок степен поузданости добијене методологије и тачности резултата, како при пројектовању нових постројења, тако и при анализи рада постојећих погона. За валидацију су коришћени резултати испитивања турбопостројења снаге од 120 до 665 MW, са поткритичним и наткритичним параметрима свеже паре. Развијени систем је више пута успешно примењен за анализу рада постројења планираних за изградњу, као и приликом разматрања модернизације постојећих блокова. Такође, систем уз неопходна проширења и интеграцију са мерним системом електра, The thesis presents a developed system for calculating heat balance diagrams of steam turbine plants and models for the simulation of the behavior of plant components. During the system's development, various models for the components that were available in the literature were analyzed. The adopted models for the calculation have been multiply validated by the conducted thermal tests of steam turbines and steam turbine plants performed in the previous period by the Laboratory for Thermal Turbomachines. In this way, a high degree of reliability of the methodology and accuracy of the results when designing new plants or analyzing existing plants' operation is achieved. During the validation, the test results of steam turbine plants with a 120 - 665 MW capacity with subcritical and supercritical parameters of fresh steam were used. Based on the developed models and systems, a computer program with a graphical interface was written, which can be used for a wide range of applications. The model for the calculation of new plants has been successfully used in the analysis of the operation of power plants that have yet to be built and the analyzes in the modernization of plants in operation. The developed program is robust, and with the short time required to perform calculations. The developed model and program for calculating heat balance diagrams of steam turbine plants are flexible, and various components can be added without restrictions. A mathematical model was developed for each component with equations that enable the calculation of the component geometry (design mode) and the simulation of operation, that is, the calculation of the component behavior under different operating conditions (analysis mode). With the necessary extensions, the developed system has been applied to monitor and analyze the operation of steam turbines, which determines the current operating characteristics of the complete plant and all its components in real-time. The system detects deviati

Methodology using the thermodynamic equilibrium composition calculation to optimise the high-temperature organic waste treatment in thermal plasma was developed. The methodology was demonstrated in the case of high-temperature treatment of polychlorinated biphenyl (PCB) in a thermal plasma reactor using two different working media, air and water vapour. Calculated results obtained in this analysis show composition of combustible and harmful chemical species formed in the PCB oil decomposition process. Optimisation of the composition of the combustibles can suggest the most economical parameters of the process. Toxic substances emissions are one of the limiting factors in the process of optimization. This analysis can be considered as the first step towards defining optimal operating parameters of the pilot-plasma facility for waste treatment from the ecological and economical aspects.

Nowadays increasing energy needs are experienced, while facing environmental issues as air pollution, global warming and acid rains. Due to many disadvantages of fossil fuels biomass is considered as a possible replacement. For energy purpose biomass could be used in direct combustion or in biogas and biodiesel production. This paper provides a review of different direct biomass combustion technologies, with emphasis on agricultural residual biomass as an energy source. Properties of biomass being used directly affect design of combustion furnace and operating parameter. Many agricultural raw materials which might be considered as a potential waste in fact have a great energy potential and when used for combustion this waste management problem can be reduced or even solved. With biomass usage potential issues are present as storage, high moisture contents, lower heating values and possible high emission of NOx during the combustion. New promising technologies and conventional combustion systems have been considered, among which are furnaces with combustion on grade, pulverized combustion, combustion in the fluidized bed and combustion in pushing furnace. Different agricultural biomass types are contemplated, alongside with applied technologies. Systematic comparison of described technologies is given in accordance with several different criteria, including overview of advantages and disadvantages. To achieve sustainable energy development, new technologies are necessary as well as advancement of the existing ones. In order for that to be achieved, it is important to systematize and categorize biomass combustion technologies.

In this study it has been presented performance analysis, from the point of First and Second Law of Thermodynamic, of an ORC for working fluids: R113, R245fa and R600a. Two heat sources were used- geothermal hot water from Vranjska Banja and wood biomass. Properties of the working fluids were obtained from Reference Fluid Properties (Refprop) and simulation was made with our own code. R600a showed better performance than R245fa with turbine power output 3.39 MW , thermal efficiency 14.01% and exergy efficiency of 33.3%.

The way to reaching the lowest value of thermal conductivity of thermal insulation materials is highly relevant for issues of energy efficiency. In order to improve thermal characteristics of traditional and new thermal insulation materials, intense research has been conducted with the goal of creating materials that are economically cost effective, and at the same time have the lowest value of thermal conductivity. Furthermore, it is also about reducing harmful effects on the environment and designing buildings with close to zero energy consumption. The paper provides an overview of characteristics of available and future thermal insulation materials, citing their advantages and disadvantages. The goal is to research which thermal insulation materials are on the way to reaching the lowest values of thermal conductivity, and their lowest possible values. Nevertheless, even though the lowest value is reached, that does not mean that these materials fulfill all requirements of sustainable and green buildings, so it is crucial to be knowledgeable about their limitations.

Nowadays people face challenges of rising energy consumption, energy costs, environmental impacts, consequence of global warming etc. All trends are directed to reduce those negative effects. In terms of energy consumption, the main goal of any production is to reduce energy consumption per product unit. At the goat farm and dairy Beocapra, located in Kukojevci in Serbia, energy was used for technological processes that include heating and cooling different types of working mediums as well as for heating and cooling spaces of the dairy. In this article the structure of used energy, energy quantities, temperature regimes and quantities of mediums and power consumption of the biggest systems were presented. The measures for improving energy efficiency and possibilities of using renewable energy sources for covering a part of energy demands were proposed. At the end of the article benefits of using proposed renewable energy sources were given.

The paper presents results of theoretical numerical research dealing with CO and NOx emission performed in the process of optimization of the performance of low-power atmospheric burners. The theoretical part of this paper, whose main goals were better understanding of the complex issues of methodology and establishment of performance prediction and optimization of low-power atmospheric gas burner included numerical variation of independent parameters, such as burner geometry, the coefficients of primary and secondary air and different gaseous fuels including biogas. The findings of theoretically obtained performance prediction and optimization of atmospheric burners were experimentally investigated in purpose built test rigs for a number of variable parameters. The obtained results fully justified the proposed models of performance prediction and burner optimization.

Održivi razvoj energetskih sistema ne sastoji se samo u korišćenju obnovljivih energetskih resursa, već i u povećanju njihove efikasnosti, što omogućava društvu da maksimizira dobrobite njihovog korišćenja. Proizvodnja električne energije iz čistih i obnovljivih izvora doprinosi smanjenju iscrpljivanja fosilnih goriva i utiče na smanjenje štetnog uticaja na životnu sredinu. Ovim se postiže globalni cilj održivog razvoja - stvaranje ravnoteže između potrošnje resursa i sposobnosti prirodnih sistema da zadovoljavaju potrebe budućih generacija. U žiži interesovanja je zaštita životne sredine. Naime, kada se procenjuje održivost energetskih sistema, pored procene ekološke održivosti (na osnovu analize životnog ciklusa - LCA), potrebno je obratiti pažnju i na smanjenje kvaliteta energije u energetskim procesima (gubitak eksergije). U ovom radu je izložen termodinamiki pristup procene održivosti energetskih sistema primenom eksergijske analize životnog ciklusa (LCEA). Naglasak je na proceni sistema koji koriste obnovljive izvore energije, i to: vetroturbini i samostalnom fotonaposnkom solarnom sistemu., The sustainable development of energy systems does not only involve the use of renewable energy resources but the increase in their efficiency as well, enabling society to maximise the benefits of their consumption. The production of electrical energy from clean and renewable sources contributes to lowered fossil fuel exploitation and the reduction of its damaging effect on the environment. This is a way to reach the global target of sustainable development - striking a balance between resource consumption and the achievable natural cycle regeneration. Environmental protection is in the focus of attention. Namely, when energy system sustainability is assessed, in addition to the ecological sustainability assessment (based on life cycle analysis - LCA), attention should be paid to the decrease in energy quality in energy processes (exergy loss). This paper presents the thermodynamic approach to energy system sustainability assessment by applying life cycle exergy analysis (LCEA). The key issue is the assessment of systems which use sustainable energy sources: the wind turbine and the stand-alone photovoltaic solar system.

This article presents experimental and numerical determinations of thermal transmittance performed on three different types of window frames (vinyl, aluminium, and wooden) within the same insulated glass unit. Good agreement between experimental and numerical results was attained. Using the numerical models, thermal improvement techniques of the frames and their influence on thermal transmittance of frames were studied. The first thermal improvement technique was using the insulation materials inserted inside large air cavities. By filling the cavity of vinyl frame with the polyurethane foam, thermal transmittance of vinyl frame was lowered by 10%. The second technique was based on repeating the procedure with materials installed inside frames with the materials that have lower thermal conductivity. This technique can be applied on thermal breaks and on steel profiles inside cavities. The result of this thermal improvement (attained by replacing thermal break material with material that has lower thermal conductivity) was certain reduction of the thermal transmittance of frames, by 9%. Using stainless steel instead of the oxidized steel was reduction of the thermal transmittance of vinyl frame by 3%. For the case of wooden frames the influence of shifting glazing unit deeper into profile upon the thermal transmittance of the frame was analyzed. Installing the glass unit by 5 mm deeper into the wooden frame reduced glass thermal transmittance by 5%.

U radu je prikazan razvijeni softverski sistem za proračun toplotnih šema postrojenja sa parnim turbinama i pripadajućim modelima za određivanje radnih parametara pojedinačnih komponenti ovakvih postrojenja. U toku razvoja ovakvog sistema analizirane su različite metode dostupne u literaturi. Na osnovu razvijenih modela i celokupne metodologije proračuna, napisan je računarski program sa grafičkim interfejsom, širokog spektra primene. Program je koncipiran i razvijen na način da poseduje fleksibilnost u pogledu konfigurisanja proračunavane toplotne šeme postrojenja, te se može primenjivati za različite tipove turbopostrojenja, s tim da se u okviru toplotne šeme različite komponente se mogu neograničeno dodavati. Za svaku od komponenti razvijen je odgovarajući matematički model koji omogućava procenu njenih geometrijskih karakteristika (dizajn mod), kao i razvijeni model koji omogućava simulaciju njenog rada pri promeni radnih uslova (analiza mod). Radni uslovi postrojenja mogu biti unapred zadati ili su rezultat merenja u toku rada realnog pogona na osnovu akvizicije i obrade podataka. Program je robustan i zahteva kratko vreme za sprovođenje proračuna. Implementirani modeli i celokupna metoda proračuna su višestruko validirani poređenjem sa rezultatima termotehničkih prijemnih i pogonskih ispitivanja parnih turbina i turbopostrojenja sprovedenih od strane Laboratorije za toplotne turbomašine i termoenergetska postrojenja Mašinskog fakulteta. Time je postignut visok stepen pouzdanosti dobijene metodologije i tačnosti rezultata, kako pri projektovanju novih postrojenja, tako i pri analizi rada postojećih pogona. Za validaciju su korišćeni rezultati ispitivanja turbopostrojenja snage od 120 do 665 MW, sa potkritičnim i natkritičnim parametrima sveže pare. Razvijeni sistem je više puta uspešno primenjen za analizu rada postrojenja planiranih za izgradnju, kao i prilikom razmatranja modernizacije postojećih blokova. Takođe, sistem uz neophodna proširenja i integraciju s, The thesis presents a developed system for calculating heat balance diagrams of steam turbine plants and models for the simulation of the behavior of plant components. During the system's development, various models for the components that were available in the literature were analyzed. The adopted models for the calculation have been multiply validated by the conducted thermal tests of steam turbines and steam turbine plants performed in the previous period by the Laboratory for Thermal Turbomachines. In this way, a high degree of reliability of the methodology and accuracy of the results when designing new plants or analyzing existing plants' operation is achieved. During the validation, the test results of steam turbine plants with a 120 - 665 MW capacity with subcritical and supercritical parameters of fresh steam were used. Based on the developed models and systems, a computer program with a graphical interface was written, which can be used for a wide range of applications. The model for the calculation of new plants has been successfully used in the analysis of the operation of power plants that have yet to be built and the analyzes in the modernization of plants in operation. The developed program is robust, and with the short time required to perform calculations. The developed model and program for calculating heat balance diagrams of steam turbine plants are flexible, and various components can be added without restrictions. A mathematical model was developed for each component with equations that enable the calculation of the component geometry (design mode) and the simulation of operation, that is, the calculation of the component behavior under different operating conditions (analysis mode). With the necessary extensions, the developed system has been applied to monitor and analyze the operation of steam turbines, which determines the current operating characteristics of the complete plant and all its components in real-time. The system detects deviati

Interes za korišćenjem rashladnih sistema, pokretanih energijom Sunca, počeo je da raste u sve većoj meri, početkom sedemdesetih godina prošlog veka. Jedan od razloga je i činjenica da konvencionalni rashladni sistemi pogonjeni kompresijom pare ili gasa, i transformacijama električne energije (sa svim problemima koje to donosi), uglavnom su na putu suprotnom od koncepta održivog razvoja. Kako se po istim principima, pored korišćenja solarne energije, mogu da koriste i različiti oblici industrijske otpadne toplote, ovakvi sistemi mogu da pomognu da se smanje problemi povezani sa štetnim uticajem na okolnu sredinu.

Researchers are becoming growgly interested in the development of solar-driven ejector cooling systems, primarily due to their potential to be used as renewable energy sources. Absorption and adsorption refrigeration systems not only involve considerable investment but are also much less reliable than the ejector refrigeration systems, which do not contain any movable parts. In addition, ejector refrigeration has the advantage of low capital cost, simple design, reliable operation, long lifespan and almost no maintenance. The only weakness of this system is the low efficiency and its intolerance to deviations from design operation condition.The paper develops a mathematical model with an algorithm which is based on the laws of thermodynamics and the principles of mass and momentum conservation. Based on the obtained model, the influence of temperature on the basic system parameters for two working fluids, R134a and R290, is presented. The working fluid temperature ranges are 80-100°C in the generator, 5-15°C in the evaporator and 33-40°C in the condenser. The important performance indicators are the characteristic ejector area ratio Ar (as a geometrical ejector parameter), ejector entrainment ratio, ejector efficiency and the COP. The results indicate that ejector geometry and working fluid type have a major impact on the ejector cooling system’s performance.

In this article is presented thermodynamic analysis of a cascade heat pump system designed for using in high-temperature heating systems The own thermodynamic model was built by using properties of working fluids from the Coo/Prop base. The cascade heat pump was designed to use ambient air as heat source with temperature t(amb )= -20 degrees C and for heating water in the high-temperature heating system up to 70 degrees C. The projected heating capacity of the cascade heat pump was 100 kW. The coefficient of performance (COP) of the cascade heat pump system due to use of different working mediums combinations in cycles of the cascade heat pump was investigated. For the best combination of working fluids (mediums) sub-cooling super-heating pressure loss in compressor's suction line, as well as exergy efficiency of the heat pump were analysed as a function of the temperature of the cascade heat exchanger.

The aim of this research is to study the drying kinetics of vacuum-dried and freeze-dried bee honey produced from two different varieties: Sunflower honey (Helianthus Annuus L.) and Acacia honey (Robinia pseudo acacia L.). Vacuum drying treatments were carried out with the honey samples' initial temperatures of +25 degrees C, -20 degrees C, and -40 degrees C. Water content, total soluble solids, as well as the water activity of fresh and dried honey samples were determined. Freeze-drying of bee honey with initial sample temperature of -40 degrees C has resulted in shorter drying time (7-9 hours), moisture content (10%-12%), water activity (0.405-0.427 aW) and effective moisture diffusivity coefficient (8.26.10-7-9.51.0-7 m(2)/s). The high-performance liquid chromatography method was used when analyzing the impact that drying pre-treatments had on honey quality. The application of pre-treatments has led to an increase in hydroxy-methyl-furfural by 39-71%, and a decrease in diastase activity by 17-36%, all compared to fresh honey samples. The solutions of Verma model proved to be the best fit with the experimental results.

More than one third of the world's primary energy demand refers to residential sector. Heating is considered as one of the main part of the energy consumption in buildings. In this study, a thermodynamic sustainability assessment analysis of different energy sources for heating of residential building, with net floor heated area of 162 m2, for Belgrade weather data, was presented. Five options of energy sources were studied, namely: coal, natural gas, electricity, district heating and air-water heat pump. Energy and exergy analyses were conducted and appropriate efficiencies were determined. Energy and exergy flows in boundaries of the building and in the whole chain from primary to final values were analyzed. The environmental impact factor and exergetic sustainability index were determined for all considered energy sources. The exergy efficiency is very low in all analyzed cases, which further implies poor thermodynamic compatibility of energy quality from the supplied side and the energy used for building heating. It was shown that the highest exergy efficiency is for the case of heat pump utilization (about 6%), due to the energy used from environment. The minimum environmental impact factor (15.37) and maximum exergetic sustainability index (0.065) were found for the case of heat pump utilization.

U radu je prikazan matematički model rada solarnog sistema za zagrevanje vode. Analizirani solarni sistem sadrži ravne solarne kolektore, dva akumulaciona rezervoara za vodu, spoljašnji razmenjivač toplote i dopunski izvor energije. Primenjeni model omogućava simulaciju rada i određivanje odgovarajućih energetskih pokazatelja rada sistema i njegovih elemenata za različite lokacije (klimatske uslove), orijentaciju kolektora, termičkih karakteristika komponenata sistema, kao i različitu dinamiku korišćenja tople vode. Rezultati simulacije su prikazani za dane tipične meteorološke godine za Beograd i dnevni profil korišćenja tople vode. Prikazana je analiza energetskih karakteristika sistema. Rezultati dobijeni numeričkom simulacijom su poređeni sa rezultatima dobijenim primenom f-chart metode proračuna., The paper presents a mathematical model of the solar water heating system. The analyzed solar system consists of flat collectors, two water storage tanks, outer heat-exchanger and a source of auxiliary energy. The implemented model enables simulation of system operation and determination of appropriate energy characteristics of the system and its elements for different locations (climatic data), orientations of collectors, thermal characteristics of system components, as well as different dynamics of hot water consumption. Results of the simulation are presented for the days of a typical meteorological year for Belgrade and the daily profile of hot water consumption. The analysis of the energy performances of the system is presented. The results obtained by simulation were compared with the results obtained with the -chart method of calculation.

According to the energy balance for Republic of Serbia for 2017, the total final energy needs for 2017 for Re-public of Serbia are estimated as 8429 Mtoe, with a share of 48% estimated for households, agricultural, public and commercial sectors. In the structure of final energy consumption by fuel for 2017 in Serbia, the renewable energy sources are participating with a share of 12% (only geothermal energy and biomass). In order to provide better under-standing of all important aspects of energy usage, beside the quantitative (energetic) analysis, it is necessary to perform also qualitative (exergetic) analysis, together with the analysis of different fuels usage impact on environment. Fuel costs should take into a consideration the value of usable part, with other words the quality of their energy, namely exergy. The paper presents thermodynamic and economic analysis of different fuels usage, for residential building, with net heated area cca 160 m2, for Belgrade weather data. Results are presented as a comparison between different fuels used for heating and domestic hot water preparation, such as: electricity, natural gas, district heating, coal and renew-able energy sources. The comparison is shown for primary energy consumption, CO2emission, exergy consumption and energy and exergy costs for different fuels.

This paper aims to explain importance of emissivity in non-contact measurement. The significance and methods of contactless temperature measurement, as well as the physics of non-contact measurement, are presented. Non-contact temperature measurement method is based on the laws of radiation. The temperature value that will be measured by this method depends on the temperature and the emissivity of the object. To understand the importance of emissivity for accurate temperature measurement, first of all the term of emissivity is explained more closely. Furthermore, the parts of the laboratory equipment, which was used to experimentally determine the influence of the object’s emissivity on the accuracy of temperature measurement, are explained. The body with known emissivity was heated and its temperature was measured using an infrared sensor. In order to predict impact of emissivity of body on accuracy of temperature measurement emissivity was varied from 0.7 to 1.0 by the software. Six body’s temperature points were used for analysis. The measured temperature values are shown, as well as the deviations of the measured temperature from the actual body temperature. The graphical representation is given for a better understanding of the measurement error caused by used wrong value of body emissivity.

U ovom radu se prikazuje originalno rešenje male, pokretne, univerzalne, ekološke, komorne, aktivne sušare za sušenje bioloških materijala, lekovitog, aromatičnog i začinskog bilja. Proces sušenja se ostvaruje solarnom energijom. Agens sušenja je smeša svežeg vazduha i izrađenog agensa sušenja. Svež vazduh se zagreva u ravnom solarnom prijemniku i transportuje se do komore za sušenje i kroz komoru za sušenje ventilatorom postavljenim na vrhu komore za sušenje. Promena položaja sušare i prijemnika omogućava optimalni prijem solarne energije tokom celog dana. PV moduli, postavljeni na krovu sušare, obezbeđuju potrebnu električnu energiju za pogon ventilatora, sistema za kontrolu i za punjenje dve akumaulatorske baterije.U radu su takođe prikazani i rezultati eksperimentalnih istraživanja kinetike procesa sušenja, koja su izvedena na prototipu solarne sušare. ., This paper presents an original design and construction of a small scale, mobile, universal, ecological, chamber, active, dryer for drying medicinal and aromatic plants and non-timber forest products. The drying process uses only solar energy. The drying agent is a mixture of hot pure air and already used drying agent from the drying chamber exhaust. Pure air is heated in flat plate solar collectors and it is pulled by an electrical fan placed on the top of the drying chamber. The mobility of the collectors and dryer provides optimal utilization of sun energy throughout the day. PV modules, placed on the roof of the dryer, generate all necessary electric power for the fan, the control system and charge a set of accumulators during the day. Experimental results and kinetics of the drying process obtained by the solar dryer prototype are also given.

The dissertation is dedicated to the local thermal discomfort impact on occupants’ productivity loss. The research was performed in real classroom, during the winter semester, for moderate climate conditions, involving voluntaries, students of the Mechanical engineering Faculty of Belgrade. The measurement had been performed for four weeks, on the different circumstances of thermal comfort conditions which had been provoked using four different scenarios and various methods. The local thermal discomfort is valuated using three scientific methods: experimental, statistical and numerical research. The improved methodology for measuring the physical parameters of the environment in real conditions was introduced. The local thermal discomfort is investigated using the key parameters: floor temperature, radiant asymmetry, vertical air difference and draught intensity. The student' skin temperature measurements are also presented, together with the results of thermal imaging camera recording used as a control method. The various statistical surveys were performed and valuable data regarding occupants’ thermal sensations and impact of local thermal comfort on working performances have been discussed. The statistical survey was conducted on young adult population, age between 20 and 25, predominantly male and healthy. The novel questionnaires had been developed, with special reference to the questions regarding local thermal comfort and occupants’ productivity loss. The productivity of the students was evaluated using the novel questionnaires and concentration test developed especially for this purpose. The productivity results were gathered based on 240 tests that had been performed. In numerical part of the survey, the novel models were developed and physical parameters were simulated using the commercial software for Computational Fluid Dynamics. The results were gathered for every point within the classroom model. These simulations can be used in a lack of measuring pos, Дисертација обухвата разматрање утицаја стања локалног топлотног дискомфора на смањење продуктивности корисника простора. Истраживање је спроведено у реалним условима, у учионици, у току зимског семестра, за умерено-континенталне климатске услове, укључујући добровољно учешће студената Машинског факултета Универзитета у Београду. Мерења су вршена током четири недеље, у различитим условима топлотног комфора, који је вариран у четири различитa сценаријa, коришћењем више метода. Локални топлотни дискомфор је оцењен анализом резулатата који су добијени коришћењем три научне методе истраживања: експерименталне, статистичке и нумеричке методе истраживања. Унапређена је методологија мерења физичких параметара унутрашње средине у реалним условима. Локални топлотни дискомфор је разматран на основу анализе више кључних параметара, као што су: температура пода, радијантна асиметрија, вертикална температурска разлика и интензитет промаје. Резултати мерења температуре површине коже студената и снимци термовизијском камером, који су коришћени као контролно мерење, су такође презентовани у раду. Различите статистичке анализе су спроведене и значајни подаци о утисцима корисника о утицају локалног топлотног комфора на смањење радне способности су разматрани. Статистичко истраживање је извршено на претежно мушкој, здравој популацији, која обухвата младе, одрасле људе, старости између 20 и 25 година. Нови упитници су развијени, са посебном пажњом усмереном на питања о локалном топлотном комфору и утицају на радну способност корисника. Продуктивност корисника је оцењена помоћу нових упитника и тестова концентрације који су развијени у оквиру истраживања. Резултати продуктивности корисника су обрађени на основу 240 тестова који су спроведени...

Истраживања у оквиру ове докторске дисертације посвећена су изучавању проблема простирања топлоте у подземном водоносном слоју, током једногодишњег рада отвореног система геотермалне топлотне пумпе (ГТП), како при континуалном, тако и при цикличном, радном режиму, као и њиховој упоредној анализи. Истраживања су спроведена помоћу нумеричког моделирања. Новоформираним нумеричко-математичким моделом обухваћена су дејстава чији утицај на температурно поље у подземном водоносном слоју до сада није детаљно проучаван: тродимензионалност развоја температурног поља, брзина струјања подземних вода, као и утицај слојевите хетерогености водоносног слоја. Истовремено, нумеричким моделом обухваћен је и утицај растојања између бунара, као и положај повратног бунара у односу на црпни бунар - низводан или узводан..., Research in the framework of the doctoral dissertation is devoted to the study of the heat transfer in the underground aquifer during the one-year operation of the open-loop ground source heat pump system (GSHP), both in the continuous and cyclical working regime, as well as in their comparative analysis. The research was carried out using numerical modelling. The newly formed numerical-mathematical model includes effects whose influence on the aquifer temperature field has not been studied in detail until now: three-dimensional development of the temperature field, the velocity of underground water flows, and the influence of the layered aquifer heterogeneity. At the same time, the numerical model also includes the influence of the distance between the wells, as well as the position of the return well relative to the pumping well - downstream or upstream...

An analysis of the absorption refrigeration system with a solution of LiBr -water as the working fluid driven by solar energy is presented in this paper. There are given the physi cal and mathematical models of the refrigeration system including two different types of solar collectors - vacuum and flat plate. Calculations of the dynamic characteristics of the system for July of the typical meteorological year for Belgrade are carried out and some of the most important technical and energy parameters are analyzed. It is shown that the application of the vacuum collectors provides many advantages over flat plate collectors.

This paper aims to present how temperature can be measured in the fastest and most accurate way using different types of sensors. It closely describes the use of simplistic temperature measurement via thermometer liquids and bimetallic thermometers, as well as the advanced measurements using thermocouples, NTC resistors, etc. Semiconductor materials which behave as ideal isolators at very low temperatures are depicted as the most slow rate response sensors, because of the time it takes for them to heat up. Whilst in most cases thermocouples type K have the quickest response time, and the most effective, due to the fact that their junction, when heated, generates thermoelectric voltage; this allows the measuring of the temperature. Also, the temperature measurement with thermistors resistance is very much explained using 2, 3, 4 -conductor connection. Furthermore, explained in detail is the main purpose which is to enable the documenting of characteristic curves via a 3 channel line recorder using measured values from the electrical temperature sensors and providing a response time through readings. In the finale stage of the paper experimental readings, calculations and measurement are shown and compered with one another according to the use of non protection tubes, tubes of high-grade steel and immersion tubes made of brass.

Istraživanja u okviru ove doktorske disertacije posvećena su izučavanju problema prostiranja toplote u podzemnom vodonosnom sloju, tokom jednogodišnjeg rada otvorenog sistema geotermalne toplotne pumpe (GTP), kako pri kontinualnom, tako i pri cikličnom, radnom režimu, kao i njihovoj uporednoj analizi. Istraživanja su sprovedena pomoću numeričkog modeliranja. Novoformiranim numeričko-matematičkim modelom obuhvaćena su dejstava čiji uticaj na temperaturno polje u podzemnom vodonosnom sloju do sada nije detaljno proučavan: trodimenzionalnost razvoja temperaturnog polja, brzina strujanja podzemnih voda, kao i uticaj slojevite heterogenosti vodonosnog sloja. Istovremeno, numeričkim modelom obuhvaćen je i uticaj rastojanja između bunara, kao i položaj povratnog bunara u odnosu na crpni bunar - nizvodan ili uzvodan..., Research in the framework of the doctoral dissertation is devoted to the study of the heat transfer in the underground aquifer during the one-year operation of the open-loop ground source heat pump system (GSHP), both in the continuous and cyclical working regime, as well as in their comparative analysis. The research was carried out using numerical modelling. The newly formed numerical-mathematical model includes effects whose influence on the aquifer temperature field has not been studied in detail until now: three-dimensional development of the temperature field, the velocity of underground water flows, and the influence of the layered aquifer heterogeneity. At the same time, the numerical model also includes the influence of the distance between the wells, as well as the position of the return well relative to the pumping well - downstream or upstream...

Предмет рада у овој дисертацији је истраживање термодинамичких процеса десалинизације морске воде методом реверзибилне осмозе..., The motivation of the research presented in this thesis was to investigate processes that appears during the desalination of seawater by reverse osmosis treatment. This research developed thermodynamic models which describes the influence of the following process operational parameters on the permeate water flux and energy consumption of seawater reverse osmosis systems: feed water pressure, feed water salinity, feed water temperature, recovery ratio and membrane permeability performance. Optimal operational conditions for the theoretical minimum energy consumption and minimum capital cost were determined. Laboratory pilot reverse osmosis skid was designed and built in order to achieve and measure all relevant reverse osmosis process parameters. Three types of membrane modules with different permeability and salt rejection properties and was tested. The chosen membrane modules were subjected to the operational parameters: feed water pressure in range 32×105 to 5 55×10 Pa, feed water stream salt concentration in range 27500 to 40000 mg/l (TDS), feed water temperature in range 15ºC to 30ºC and recovery rate of the system in range 42 to 51%. The results confirmed that the salt concentration of feed water and recovery rate have significant impacts on the energy consumption of the system, while on the other side the temperature of feed water significantly affects the quality of permeate water. It was discovered that appropriate selection of membrane modules, configuration of membrane elements and operating parameters could increase system energy efficiency and reduce specific energy consumption of produced permeate water volume. The results of thermodynamic model equation were compared with the experimental results and with the models of the other authors in order to be verified. Aspects of the integration of reversible osmosis water system with photovoltaic cells with purpose of further optimizing the energy consumption was presented.