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15 results on '"Rudonja, Nedžad"'

2. Numerical simulation of thermo-fluid properties and optimization of hot water storage tank in biomass heating systems

Author

Živković Goran S., Mirkov Nikola S., Dakić Dragoljub V., Mladenović Milica R., Erić Aleksandar M., Erić Milić D., and Rudonja Nedžad R.

Subjects
heat storage, numerical simulation, measurements, combustion, biomass, Engineering (General). Civil engineering (General), TA1-2040, Mechanics of engineering. Applied mechanics, TA349-359
Abstract

A 1.5 MW combustion facility burning large bales of soy straw has been built for the purpose of heating 1 ha of vegetable greenhouses located within the complex of Agricultural Plant PKB in Padinska Skela, Serbia. The paper addresses numerical and experimental study of temperature distribution in a cylindrical, 100 m3 (8 m high, 4 m in diameter) hot water storage tank. The water tank optimization, as well as optimization of the heating facility as a whole, were identified as the main goals of the study performed. Water temperature was measured by a temperature probe inserted in the tank. Measurements were conducted in 256 measurement points, both under steady and unsteady water flow conditions. Water tank optimization analysis was carried out utilizing both steady and unsteady state numerical simulation. The results obtained indicated good agreement between the experimental and computational data acquired.

Published
2010

4. EXPERIMENTAL AND NUMERICAL INVESTIGATION OF THERMAL IMPROVEMENT OF WINDOW FRAMES.

Author

GOJAK, Milan D., KIJANOVIĆ, Aleksandar I., RUDONJA, Nedžad R., and TODOROVIĆ, Ružica I.

Subjects
THERMAL conductivity, URETHANE foam, INSULATING materials, STAINLESS steel, VINYL ester resins
Abstract

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%. [ABSTRACT FROM AUTHOR]

Published
2021
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5. STUDY OF VACUUM AND FREEZE DRYING OF BEE HONEY.

Author

NEDIĆ, Nebojša M., GOJAK, Milan D., ZLATANOVIĆ, Ivan J., RUDONJA, Nedžad R., LAZAREVIĆ, Kristina B., DRAŽIĆ, Milan S., GLIGOREVIĆ, Kosta B., and PAJIĆ, Miloš B.

Subjects
HONEYBEES, FREEZE-drying, DRYING, HIGH performance liquid chromatography, COMMON sunflower, VACUUM, HONEY
Abstract

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 °C, -20 °C, and -40 °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°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 (8.26·10-7-9.51·10-7 m²/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. [ABSTRACT FROM AUTHOR]

Published
2020
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6. Побољшање преношења топлоте у акумулатору топлоте са фазно променљивим материјалом као испуном

Author

Rudonja, Nedžad R., Komatina, Mirko, Banjac, Miloš, Gojak, Milan, Antonijević, Dragi, and Živković, Goran

Subjects
нумеричко моделирање, парафин, phase-change material, numerical modeling, акумулатор топлоте, thermal energy storage, фазно променљив материјал, paraffin
Abstract

Отежано преношење топлоте у акумулаторима топлоте са фазно променљивим материјалом као испуном, које се јавља као последица мале топлотне проводљивости фазно променљивих материјала који се користе на температурском опсегу до 200 C° , представља главну препреку у примени акумулатора топлоте у којима се акумулација топлоте остварује на рачун промене фазе радног медијума. Поред типова акумулатора топлоте и прегледа потенцијалних, односно коришћених фазно променљивих материјала, разматране су методе за побољшање преношења топлоте, тј. за превазилажење проблема мале топлотне проводљивости материјала. Као најпоузданији метод за поспешивање преношења топлоте се показало повећање површи за размену топлоте, тј. површи која је у контакту са фазно променљивим материјалом. Као фазно променљиви материјал коришћен је парафин комерцијалног назива Е53. Побољшање преношења топлоте је праћено преко смањења времена топљења парафина, тј. повећања брзине промене фазе, односно временског периода у коме се достиже температура промене фазе парафина. За разлику од досадашњих истраживања, у којима је повећање оствареног побољшања преношења топлоте посматрано у функцији од броја ребара или неке карактеристичне димензије ребра (висина, пречник, дужина и сл.), у овом раду је побољшање доведено у корелацију са фактором оребрења. У оквиру дисертације је осмишљен физички модел акумулатора топлоте испуњеног фазно променљивим материјалом за три вредности фактора оребрења, тј. за три варијанте акумулатора топлоте. Уведени физички модел акумулатора топлоте описан је одговарајућим математичким моделом у који су имплементиране претпоставке неопходне за решавање дефинисаног система једначина... Impaired heat transfer in thermal energy storage (TES) with phase change material (PCM) as a filling, which occurs as a result of low thermal conductivity of the phase-change materials used for storing thermal energy up to 200 C° , represents a major obstacle in the implementation of the TES in which the heat accumulation is realized as a consequence of the working medium phase change. Beside review of present thermal energy storages types and potential one, respectively used PCMs, methods for enhancing heat transfer were considered, i.e. method for overcoming the problem of low thermal conductivity material. As the most reliable method for enhancing heat transfer, the increase of heat transfer surface was found, i.e. the surface that is in the contact with PCM. The commercial paraffin E53 was used as the PCM. The enhancement of heat transfer is accompanied by the decrease of the paraffin melting time, i.e. increase of the phase change rate, respectively the period in which the temperature of the phase change of the paraffin is reached. Unlike previous studies, where achieved heat transfer increase was analyzed as a function of the number of fins or some fin characteristic dimension (height, diameter, length, etc.), in this thesis the heat transfer improvement was into correlated with of the finned surface factor. Within this thesis the physical model of the thermal energy storage filled by PCM was conceived for three values of the finned surface factor, i.e. for the three variants of the TES. The introduced physical model of the TES was described by corresponding mathematical model in which the necessary assumptions for solving the defined system of equations were implemented...

Published
2016

7. GREEN ROOFS AND COOL MATERIALS AS RETROFITTING STRATEGIES FOR URBAN HEAT ISLAND MITIGATION: Case Study in Belgrade, Serbia.

Author

LALOŠEVIĆ, Marija D., KOMATINA, Mirko S., MILOŠ, Marko V., and RUDONJA, Nedžad R.

Subjects
URBAN heat islands, ROOF gardening, SUSTAINABLE buildings, RENEWABLE energy sources, METROPOLITAN areas
Abstract

The effect of extensive and intensive green roofs on improving outdoor microclimate parameters of urban built environments is currently a worldwide focus of research. Due to the lack of reliable data for Belgrade, the impact of extensive and intensive green roof systems on mitigating the effects of urban heat islands and improving microclimatic conditions by utilizing high albedo materials in public spaces were studied. Research was conducted on four chosen urban units within existing residential blocks in the city that were representative of typical urban planning and construction within the Belgrade metropolitan area. Five different models (baseline model and four potential models of retrofitting) were designed, for which the temperature changes at pedestrian and roof levels at 07:00, 13:00, 19:00 h, on a typical summer day, and at 01:00 h, the following night in Belgrade were investigated. The ENVI-met software was used to model the simulations. The results of numerical modeling showed that utilizing green roofs in the Belgrade climatic area could reduce air temperatures in the surroundings up to 0.47, 1.51, 1.60, 1.80 °C at pedestrian level and up to 0.53, 1.45, 0.90, 1.45 °C at roof level for four potential retrofitting strategies, respectively. [ABSTRACT FROM AUTHOR]

Published
2018
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8. Experimental investigation on accumulation of heat by phase change material in the thermal energy storage

Author

Rudonja, Nedžad R., Živković, Goran S., Komatina, Mirko S., and Repić, Branislav S.

Subjects
phase change, thermal energy storage, paraffin
Abstract

The paper includes a general discussion of reasons for the application of heat storage and phase change material as storage medium. A part of experimental results obtained by measuring during the process of paraffin phase change was presented. It was observed that in order to obtain lower temperature stratification during the heating process it is necessary to increase the number of volume heat sources in the thermal storage. .

Published
2012

9. Primena toplotnih pumpi u sistemima za sušenje prehrambenih proizvoda

Author

Zlatanović, Ivan, Rudonja, Nedžad, and Gligorević, Kosta

Subjects
heat pump, koeficijent grejanja, energetska efikasnost, toplotna pumpa, sušenje, drying, coefficient of performance, energy efficiency
Abstract

Heat pump drying systems application has great potential and provides economical and ecological benefit in food industry. Many researchers deal with a problem of investigating heat pump drying system performance. However, there have not been any massive applications of these systems on farms and in food industry in Republic of Serbia, considering huge effort of their promotion. This paper analyze performances of typical drying systems configurations from the COP and specific compressor work point of view, considering different outside influences and operating conditions. . Upotreba toplotnih pumpi obećava ekonomski i ekološki benefit i veliki broj istraživanja se bavi njihovom primenom u sistemima sušenja prehrambenih proizvoda. Međutim, do njihove masovnije upotrebe u Republici Srbiji na farmama i u industriji još uvek nije došlo uprkos uloženim naporima i promovisanju. U ovom radu analizirane su performanse rada tipičnih konfiguracija sistema sušenja sa stanovišta postizanja maksimalnog koeficijenta grejanja pod određenim spoljnim uticajima i u zavisnosti od željenog režima sušenja. .

Published
2011

10. Energy efficiency analysis of corn seed drying process in Maize Research Institute 'Zemun Polje' - Zemun

Author

Zlatanović, Ivan, Gligorević, Kosta, Radojičić, Dušan, Dražić, Milan, Oljača, Mićo V., Dumanović, Zoran, Mišović, Miloš, Manić, Nebojša, and Rudonja, Nedžad

Subjects
natural gas, ekologija, corn seed, energetska efikasnost, prirodni gas, sušenje, drying, corncob, ecology, semenski kukuruz, energy efficiency, oklasak
Abstract

In this paper actual parameter analysis of corn seed energy efficiency drying process was performed in Maize Research Institute 'Zemun Polje' in Zemun. Energy consumption data and performances of old - natural gas based system and new - corncob combustion based system were compared and analyzed. This paper deals with basic improvement measures, biomass usage and corncob usage validation in this type of industrial systems. . U ovom radu je analizirana i ispitana energetska efikasnost sušenja semenskog kukuruza u doradnom centru Instituta za kukuruz 'Zemun Polje' u Zemunu. Podaci o radu starog sistema sušenja koji je kao energent koristio prirodni gas, analizirani su i upoređeni sa energetskim parametrima novog sistema, koji kao energent koristi usitnjeni oklasak dobijen u procesu krunjenja semenskog kukuruza. Rad se takođe bavi i razmatranjem ekoloških aspekata korišćenja oklaska kao goriva i tehno-ekonomskom opravdanošću primene ovakvog sistema sušenja. .

Published
2011

11. Condensing dryer with full air recirculation for agriculture application

Author

Zlatanović, Ivan, Rudonja, Nedžad, and Gligorević, Kosta

Subjects
ekologija, efficiency, regulation, sušenje, drying, ecology, energija, efikasnost, regulacija, energy
Abstract

Condensing dryer for agriculture application has notable advantages comparing with traditional drying methods, within fact that drying process is at low-temperature regime. Negative influence of dried fiber structure is minimized with full air recirculation. This technology is 'eco-friendly' and has no considerable effect on environment and ecology in negative meaning. Basics principles of most applied standards in food industry are mentioned in this paper. Kondenzaciona sušara ima i prednost u odnosu na druge metode sušenja u činjenici da je kod nje proces sušenja na niskotemperaturskom režimu što je veoma pogodno kod sušenja sirovine gde zahteva minimalan uticaj samog procesa na strukturu vlakana u negativnom smislu. Ova tehnologija sušenja spada u 'eco-friendly' ekološki prihvatljive tehnologije, što znači da nema bitnog uticaja na životnu sredinu i okruženje u kome se nalazi. U radu su predstavljene osobine ovakvog načina sušenja sa aspekta primene osnovnih principa strogih standarda prehrambene industrije.

Published
2010

12. HEAT TRANSFER ENHANCEMENT THROUGH PCM THERMAL STORAGE BY USE OF COPPER FINS.

Author

RUDONJA, Nedžad R., KOMATINA, Mirko S., ŽIVKOVIĆ, Goran S., and ANTONIJEVIĆ, Dragi Lj.

Subjects
*HEAT storage, *FINS (Engineering), *HEAT transfer, *HEAT flux, *NUMERICAL analysis
Abstract

Enhancement of heat transfer over a cylinder shaped thermal energy storage filled by paraffin E53 by use of longitudinal rectangular copper fins was analyzed. The thermo-physical features of the storage material are determined in separate experiments and implemented to FLUENT software over user defined function. Advanced thermal storage geometry comprehension and optimization required introduction of a parameter suitable for the analysis of heat transfer enhancement, so the ratio of heat transfer surfaces as a factor was proposed and applied. It is revealed that increase of the ratio of heat transfer surfaces leads to the decrease of melting time and vice versa. Numerical analysis, employing the 3-D model built in Ansys software, observed storage reservoir geometries with variable number of longitudinal fins. The adjusted set of boundary conditions was carried out and both written in C language and implemented over user defined function in order to define variable heat flux along the height of the heater. The comparison of acquired numerical and experimental results showed a strong correlation. Experimental validation of numerical results was done on the real thermal energy storage apparatus. [ABSTRACT FROM AUTHOR]

Published
2016
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15. Термодинамичка анализа, моделирање и оптомизација динамичког понашања система за климатизацију, грејање и хлађење у јавним објектима

Author

Manić, Dimitrije, Komatina, Mirko, Banjac, Miloš, Živković, Branislav, Rudonja, Nedžad, and Vučićević, Biljana

Subjects
енергетске перформансе зграда, термички омотач, КГХ системи калибрисана симулација, мере за уштеду енергије, емисија гасова стаклене баште, building energy performance, thermal envelope, HVAC systems, calibrated simulation, energy saving measures, greenhouse gasses emission
Abstract

У контексту повећања ефикасности и одрживости енергетског сектора, један од најзначајнијих проблема представља рационализација и оптимизација потрошње енергије у зградама, јер oко 32% глобалне потрошње енергије је у сектору зграда [1]. Значајни напори на глобалном и ло- калном нивоу улажу се у повећање енергетске ефикасности у зградама, укључујући унапре- ђење индустријских стандарда, међународних уговора, законске регулативе и инвестирање у енергетске санације постојећих зграда и енергетски ефикасне технологије... In contexts of sustainability and energy efficiency, one of the most important topics is rationalization and optimization of building energy consumption, since about 32% of total energy consumption in the world is from the building sector [1]. Significant efforts and resources on global and local level are invested in order to increase energy efficiency of the buildings, including improving industrial standards, international agreements, legislation and investment in energy efficient technology, and energy retrofits of existing buildings...

Published
2021

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