TY  - JOUR
AU  - Rudonja, Nedzad R.
AU  - Komatina, Mirko S.
AU  - Živković, Goran S.
AU  - Antonijević, Dragi Lj.
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1148
AB  - 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.
T2  - Thermal Science
T1  - Heat Transfer Enhancement Through Pcm Thermal Storage By Use of Copper Fins
VL  - 20
SP  - S251
EP  - S259
DO  - 10.2298/TSCI150729136R
ER  - 

@article{
author = "Rudonja, Nedzad R. and Komatina, Mirko S. and Živković, Goran S. and Antonijević, Dragi Lj.",
year = "2016",
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.",
journal = "Thermal Science",
title = "Heat Transfer Enhancement Through Pcm Thermal Storage By Use of Copper Fins",
volume = "20",
pages = "S251-S259",
doi = "10.2298/TSCI150729136R"
}

Rudonja, N. R., Komatina, M. S., Živković, G. S.,& Antonijević, D. Lj.. (2016). Heat Transfer Enhancement Through Pcm Thermal Storage By Use of Copper Fins. in Thermal Science, 20, S251-S259.
https://doi.org/10.2298/TSCI150729136R

Rudonja NR, Komatina MS, Živković GS, Antonijević DL. Heat Transfer Enhancement Through Pcm Thermal Storage By Use of Copper Fins. in Thermal Science. 2016;20:S251-S259.
doi:10.2298/TSCI150729136R .

Rudonja, Nedzad R., Komatina, Mirko S., Živković, Goran S., Antonijević, Dragi Lj., "Heat Transfer Enhancement Through Pcm Thermal Storage By Use of Copper Fins" in Thermal Science, 20 (2016):S251-S259,
https://doi.org/10.2298/TSCI150729136R . .

TY  - JOUR
AU  - Rudonja, Nedzad R.
AU  - Komatina, Mirko S.
AU  - Antonijević, Dragi Lj.
AU  - Živković, Goran S.
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7151
AB  - Precise understanding of heat transfer processes inside the latent thermal energy storage exposed to different initial and boundary conditions is crucial for development of optimized design and operating features of similar devices. The paper presents 3D numerical study of phase change material heat storage in the shape of vertical cylinder reservoir with axially placed heat source/sink equipped with variable number of conductance enhancing longitudinal rectangular fins. As the principally important observed is the case of vertically variable heat flux supplied to the phase change material during the melting process. The numerical modeling is based on the physical model of the process and is being carried out by Fluent software that uses finite volume method for solving continuity, momentum and energy equations. The coupling between pressure and velocity is based on the Semi- Implicit Pressure- Linked Equation (SIMPLE) algorithm. The results of numerical simulations are verified through the comparison with the own experimental results. Exemplary results for characteristic heat storage geometries and boundary conditions are presented and analyzed in the paper.
T2  - Bulgarian Chemical Communications
T1  - Numerical simulation of latent heat storage with conductance enhancing fins
VL  - 48
SP  - 199
EP  - 205
UR  - https://hdl.handle.net/21.15107/rcub_vinar_7151
ER  - 

@article{
author = "Rudonja, Nedzad R. and Komatina, Mirko S. and Antonijević, Dragi Lj. and Živković, Goran S.",
year = "2016",
abstract = "Precise understanding of heat transfer processes inside the latent thermal energy storage exposed to different initial and boundary conditions is crucial for development of optimized design and operating features of similar devices. The paper presents 3D numerical study of phase change material heat storage in the shape of vertical cylinder reservoir with axially placed heat source/sink equipped with variable number of conductance enhancing longitudinal rectangular fins. As the principally important observed is the case of vertically variable heat flux supplied to the phase change material during the melting process. The numerical modeling is based on the physical model of the process and is being carried out by Fluent software that uses finite volume method for solving continuity, momentum and energy equations. The coupling between pressure and velocity is based on the Semi- Implicit Pressure- Linked Equation (SIMPLE) algorithm. The results of numerical simulations are verified through the comparison with the own experimental results. Exemplary results for characteristic heat storage geometries and boundary conditions are presented and analyzed in the paper.",
journal = "Bulgarian Chemical Communications",
title = "Numerical simulation of latent heat storage with conductance enhancing fins",
volume = "48",
pages = "199-205",
url = "https://hdl.handle.net/21.15107/rcub_vinar_7151"
}

Rudonja, N. R., Komatina, M. S., Antonijević, D. Lj.,& Živković, G. S.. (2016). Numerical simulation of latent heat storage with conductance enhancing fins. in Bulgarian Chemical Communications, 48, 199-205.
https://hdl.handle.net/21.15107/rcub_vinar_7151

Rudonja NR, Komatina MS, Antonijević DL, Živković GS. Numerical simulation of latent heat storage with conductance enhancing fins. in Bulgarian Chemical Communications. 2016;48:199-205.
https://hdl.handle.net/21.15107/rcub_vinar_7151 .

Rudonja, Nedzad R., Komatina, Mirko S., Antonijević, Dragi Lj., Živković, Goran S., "Numerical simulation of latent heat storage with conductance enhancing fins" in Bulgarian Chemical Communications, 48 (2016):199-205,
https://hdl.handle.net/21.15107/rcub_vinar_7151 .

TY  - JOUR
AU  - Erić, Aleksandar
AU  - Komatina, M.
AU  - Nemoda, Stevan
AU  - Dakić, Dragoljub V.
AU  - Repić, Branislav
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/966
AB  - Modeling of transport phenomena in materials with porous bed features requires thermophysical properties, such as porosity, permeability and thermal conductivity be known. The paper presents experimental data obtained in the course of investigation focused on analysis of stagnant thermal conductivity of biomass. Experiments were conducted using a custom designed and constructed experimental setup and implementing original experimental procedure. Results obtained enabled stagnant thermal conductivity of biomass to be determined for different biomass porosity values. Analysis of the experimental data enabled functional dependence of stagnant thermal conductivity on porosity to be determined, with porosity varied in a range 0.50-0.85. Results obtained indicate that reduced bed porosity, down to the value of 0.65, causes stagnant thermal conductivity of the bed to be reduced. Further porosity reduction, below the value of 0.65, results in increased stagnant thermal conductivity of the bed. Experimental procedure developed shall be useful for gathering experimental data on different materials planned to be analyzed when examining transport phenomena occurring during combustion of biomass bales. In addition, data to be acquired shall be helpful in modeling the transport phenomena associated with combustion in porous beds. (C) 2015 Elsevier Ltd. All rights reserved.
PB  - Elsevier
T2  - Renewable and Sustainable Energy Reviews
T1  - Determination of thermal conductivity of baled agricultural biomass
VL  - 58
SP  - 876
EP  - 884
DO  - 10.1016/j.rser.2015.12.066
ER  - 

@article{
author = "Erić, Aleksandar and Komatina, M. and Nemoda, Stevan and Dakić, Dragoljub V. and Repić, Branislav",
year = "2016",
abstract = "Modeling of transport phenomena in materials with porous bed features requires thermophysical properties, such as porosity, permeability and thermal conductivity be known. The paper presents experimental data obtained in the course of investigation focused on analysis of stagnant thermal conductivity of biomass. Experiments were conducted using a custom designed and constructed experimental setup and implementing original experimental procedure. Results obtained enabled stagnant thermal conductivity of biomass to be determined for different biomass porosity values. Analysis of the experimental data enabled functional dependence of stagnant thermal conductivity on porosity to be determined, with porosity varied in a range 0.50-0.85. Results obtained indicate that reduced bed porosity, down to the value of 0.65, causes stagnant thermal conductivity of the bed to be reduced. Further porosity reduction, below the value of 0.65, results in increased stagnant thermal conductivity of the bed. Experimental procedure developed shall be useful for gathering experimental data on different materials planned to be analyzed when examining transport phenomena occurring during combustion of biomass bales. In addition, data to be acquired shall be helpful in modeling the transport phenomena associated with combustion in porous beds. (C) 2015 Elsevier Ltd. All rights reserved.",
publisher = "Elsevier",
journal = "Renewable and Sustainable Energy Reviews",
title = "Determination of thermal conductivity of baled agricultural biomass",
volume = "58",
pages = "876-884",
doi = "10.1016/j.rser.2015.12.066"
}

Erić, A., Komatina, M., Nemoda, S., Dakić, D. V.,& Repić, B.. (2016). Determination of thermal conductivity of baled agricultural biomass. in Renewable and Sustainable Energy Reviews
Elsevier., 58, 876-884.
https://doi.org/10.1016/j.rser.2015.12.066

Erić A, Komatina M, Nemoda S, Dakić DV, Repić B. Determination of thermal conductivity of baled agricultural biomass. in Renewable and Sustainable Energy Reviews. 2016;58:876-884.
doi:10.1016/j.rser.2015.12.066 .

Erić, Aleksandar, Komatina, M., Nemoda, Stevan, Dakić, Dragoljub V., Repić, Branislav, "Determination of thermal conductivity of baled agricultural biomass" in Renewable and Sustainable Energy Reviews, 58 (2016):876-884,
https://doi.org/10.1016/j.rser.2015.12.066 . .

TY  - JOUR
AU  - Mitrovic, Danica
AU  - Dokovic, Natasa
AU  - Zivotic, Dragana
AU  - Bechtel, Achim
AU  - Sajnovic, Aleksandra
AU  - Stojanovic, Ksenija
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7143
AB  - The origin of the organic matter (OM) and the characteristics of the depositional environment of lignites from the Upper Miocene Kovin deposit (hosting three coal seams) of Serbia were evaluated based on petrographic data, bulk organic geochemical parameters, biomarker analysis and stable isotope geochemistry (delta C-13 of individual biomarkers). Samples were collected from four boreholes, GD-601 and GD-603 (the A field), and KB-79 and KB-91 (the B field), representing different parts of coal seams I, II, and III. Investigated lignites are typical humic coals. The OM of lignites is derived from woody vegetation and herbaceous peat-forming plants, with prevalence of the former in most samples. Peat-forming vegetation is characterized by abundant decay resistant gymnosperm (coniferous) plants, followed by a low amount of angiosperms. Lignite forming plants mostly belonged to the gymnosperm families Cupressaceae, Taxodiaceae, Phyllocladaceae and Pinaceae. Slight input of ferns, fungi and aquatic macrophyta to lignite OM is also evident. Distributions of hopanoids and isotopic compositions of these biomarkers reflect the activity of various microbial populations represented by methanotrophic-, chemoautotrophic- and heterotrophic bacteria during diagenesis. Prominent C-28 28,30-bisnorneohop-13(18)-ene was observed for the first time in the lignite extracts. According to the delta C-13 value it was probably derived from chemoautotrophic bacteria. C28 28,30-bisnorneohop-13(18)-ene could be one of the possible precursors of a series of orphan aromatic hopanoids bearing an ethyl group at C-21, via progressive aromatization. Peatification proceeded in a fresh water environment under variable redox conditions, from anoxic to slightly oxic. All three coal seams are heterogeneous. The lower parts of the coal seams represent a topogenous fresh water peat mire with open water areas, which was subjected to inundations. The upper parts of coal seams represent a wet forest swamp with relatively stable conditions. Despite the observed variations in all three coal seams, the mean values of petrographic and organic geochemical parameters suggest general increasing of wetness and establishment of more stable conditions from seam III to seam I. Maceral and biomarker data indicate that rapid flooding of the bogs stopped peat growth in all three coal seams. Relatively frequent variations in all three coal seams, followed by repetition of lignite characteristics depict well the pronounced seasonality e.g. short term cycles of the climate during Late Miocene in investigated area. (C) 2016 Elsevier B.V. All rights reserved.
T2  - International Journal of Coal Geology
T1  - Petrographical and organic geochemical study of the Kovin lignite deposit, Serbia
VL  - 168
SP  - 80
EP  - 107
DO  - 10.1016/j.coal.2016.07.008
ER  - 

@article{
author = "Mitrovic, Danica and Dokovic, Natasa and Zivotic, Dragana and Bechtel, Achim and Sajnovic, Aleksandra and Stojanovic, Ksenija",
year = "2016",
abstract = "The origin of the organic matter (OM) and the characteristics of the depositional environment of lignites from the Upper Miocene Kovin deposit (hosting three coal seams) of Serbia were evaluated based on petrographic data, bulk organic geochemical parameters, biomarker analysis and stable isotope geochemistry (delta C-13 of individual biomarkers). Samples were collected from four boreholes, GD-601 and GD-603 (the A field), and KB-79 and KB-91 (the B field), representing different parts of coal seams I, II, and III. Investigated lignites are typical humic coals. The OM of lignites is derived from woody vegetation and herbaceous peat-forming plants, with prevalence of the former in most samples. Peat-forming vegetation is characterized by abundant decay resistant gymnosperm (coniferous) plants, followed by a low amount of angiosperms. Lignite forming plants mostly belonged to the gymnosperm families Cupressaceae, Taxodiaceae, Phyllocladaceae and Pinaceae. Slight input of ferns, fungi and aquatic macrophyta to lignite OM is also evident. Distributions of hopanoids and isotopic compositions of these biomarkers reflect the activity of various microbial populations represented by methanotrophic-, chemoautotrophic- and heterotrophic bacteria during diagenesis. Prominent C-28 28,30-bisnorneohop-13(18)-ene was observed for the first time in the lignite extracts. According to the delta C-13 value it was probably derived from chemoautotrophic bacteria. C28 28,30-bisnorneohop-13(18)-ene could be one of the possible precursors of a series of orphan aromatic hopanoids bearing an ethyl group at C-21, via progressive aromatization. Peatification proceeded in a fresh water environment under variable redox conditions, from anoxic to slightly oxic. All three coal seams are heterogeneous. The lower parts of the coal seams represent a topogenous fresh water peat mire with open water areas, which was subjected to inundations. The upper parts of coal seams represent a wet forest swamp with relatively stable conditions. Despite the observed variations in all three coal seams, the mean values of petrographic and organic geochemical parameters suggest general increasing of wetness and establishment of more stable conditions from seam III to seam I. Maceral and biomarker data indicate that rapid flooding of the bogs stopped peat growth in all three coal seams. Relatively frequent variations in all three coal seams, followed by repetition of lignite characteristics depict well the pronounced seasonality e.g. short term cycles of the climate during Late Miocene in investigated area. (C) 2016 Elsevier B.V. All rights reserved.",
journal = "International Journal of Coal Geology",
title = "Petrographical and organic geochemical study of the Kovin lignite deposit, Serbia",
volume = "168",
pages = "80-107",
doi = "10.1016/j.coal.2016.07.008"
}

Mitrovic, D., Dokovic, N., Zivotic, D., Bechtel, A., Sajnovic, A.,& Stojanovic, K.. (2016). Petrographical and organic geochemical study of the Kovin lignite deposit, Serbia. in International Journal of Coal Geology, 168, 80-107.
https://doi.org/10.1016/j.coal.2016.07.008

Mitrovic D, Dokovic N, Zivotic D, Bechtel A, Sajnovic A, Stojanovic K. Petrographical and organic geochemical study of the Kovin lignite deposit, Serbia. in International Journal of Coal Geology. 2016;168:80-107.
doi:10.1016/j.coal.2016.07.008 .

Mitrovic, Danica, Dokovic, Natasa, Zivotic, Dragana, Bechtel, Achim, Sajnovic, Aleksandra, Stojanovic, Ksenija, "Petrographical and organic geochemical study of the Kovin lignite deposit, Serbia" in International Journal of Coal Geology, 168 (2016):80-107,
https://doi.org/10.1016/j.coal.2016.07.008 . .

TY  - JOUR
AU  - Mladenović, Milica R.
AU  - Dakić, Dragoljub V.
AU  - Nemoda, Stevan
AU  - Mladenovic, Rastko V.
AU  - Erić, Aleksandar
AU  - Repić, Branislav
AU  - Komatina, Mirko S.
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4822
AB  - In this paper a method of examination of fuel suitability for fluidized bed combustion is presented. The research of combustion characteristics of low grade fractions of Lubnica brown coal in the fluidized bed by the aforementioned methodology has been carried out on a laboratory semi-industrial apparatus of 200 kW(t). Description of the experimental fluidized bed combustion facility is given, as well as experimental results, with the focus on furnace temperature distribution, in order to determine the location of the zone of intensive combustion. Based on investigation results, which are focused on combustion quality (combustion completion) as well as on satisfying the environmental protection criteria, it can be stated that the investigated coal is suitable for burning in bubbling, as well as in circulating fluidized bed.
T2  - Thermal Science
T1  - Combustion of Low Grade Fractions of Lubnica Coal in Fluidized Bed
VL  - 16
IS  - 1
SP  - 297
EP  - 311
DO  - 10.2298/TSCI1201297M
ER  - 

@article{
author = "Mladenović, Milica R. and Dakić, Dragoljub V. and Nemoda, Stevan and Mladenovic, Rastko V. and Erić, Aleksandar and Repić, Branislav and Komatina, Mirko S.",
year = "2012",
abstract = "In this paper a method of examination of fuel suitability for fluidized bed combustion is presented. The research of combustion characteristics of low grade fractions of Lubnica brown coal in the fluidized bed by the aforementioned methodology has been carried out on a laboratory semi-industrial apparatus of 200 kW(t). Description of the experimental fluidized bed combustion facility is given, as well as experimental results, with the focus on furnace temperature distribution, in order to determine the location of the zone of intensive combustion. Based on investigation results, which are focused on combustion quality (combustion completion) as well as on satisfying the environmental protection criteria, it can be stated that the investigated coal is suitable for burning in bubbling, as well as in circulating fluidized bed.",
journal = "Thermal Science",
title = "Combustion of Low Grade Fractions of Lubnica Coal in Fluidized Bed",
volume = "16",
number = "1",
pages = "297-311",
doi = "10.2298/TSCI1201297M"
}

Mladenović, M. R., Dakić, D. V., Nemoda, S., Mladenovic, R. V., Erić, A., Repić, B.,& Komatina, M. S.. (2012). Combustion of Low Grade Fractions of Lubnica Coal in Fluidized Bed. in Thermal Science, 16(1), 297-311.
https://doi.org/10.2298/TSCI1201297M

Mladenović MR, Dakić DV, Nemoda S, Mladenovic RV, Erić A, Repić B, Komatina MS. Combustion of Low Grade Fractions of Lubnica Coal in Fluidized Bed. in Thermal Science. 2012;16(1):297-311.
doi:10.2298/TSCI1201297M .

Mladenović, Milica R., Dakić, Dragoljub V., Nemoda, Stevan, Mladenovic, Rastko V., Erić, Aleksandar, Repić, Branislav, Komatina, Mirko S., "Combustion of Low Grade Fractions of Lubnica Coal in Fluidized Bed" in Thermal Science, 16, no. 1 (2012):297-311,
https://doi.org/10.2298/TSCI1201297M . .

TY  - JOUR
AU  - Erić, Aleksandar
AU  - Dakić, Dragoljub V.
AU  - Nemoda, Stevan
AU  - Komatina, Mirko
AU  - Repić, Branislav
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/5055
AB  - The paper presents the results of an experimental investigation conducted to determine the permeability coefficients and the stagnant thermal conductivity i.e. the thermo physical properties deemed to be the most important features of the bed material when considering combustion in pusher-type furnaces (i.e. combustion of biomass bales in cigar burners). The appropriate experimental methods have been developed and suitable experimental apparatus designed and constructed in order to determine permeability and stagnant thermal conductivity coefficient of the soybean straw bales. The experimental investigation conducted was aimed at examining the effects of relevant biomass bale parameters on the aforementioned coefficients. Based on the numerous measurements performed, correlations were obtained that are deemed highly important for optimization of the biomass bale combustion, as well as for modeling the transport phenomena occurring in the porous bed formed during biomass bales combustion in cigar burners. Data collected during the course of research investigation were used to develop a detailed CFD model of straw bales combustion in cigar burners. (C) 2012 Elsevier Ltd. All rights reserved.
T2  - Energy
T1  - Experimental determination thermo physical characteristics of balled biomass
VL  - 45
IS  - 1
SP  - 350
EP  - 357
DO  - 10.1016/j.energy.2012.02.063
ER  - 

@article{
author = "Erić, Aleksandar and Dakić, Dragoljub V. and Nemoda, Stevan and Komatina, Mirko and Repić, Branislav",
year = "2012",
abstract = "The paper presents the results of an experimental investigation conducted to determine the permeability coefficients and the stagnant thermal conductivity i.e. the thermo physical properties deemed to be the most important features of the bed material when considering combustion in pusher-type furnaces (i.e. combustion of biomass bales in cigar burners). The appropriate experimental methods have been developed and suitable experimental apparatus designed and constructed in order to determine permeability and stagnant thermal conductivity coefficient of the soybean straw bales. The experimental investigation conducted was aimed at examining the effects of relevant biomass bale parameters on the aforementioned coefficients. Based on the numerous measurements performed, correlations were obtained that are deemed highly important for optimization of the biomass bale combustion, as well as for modeling the transport phenomena occurring in the porous bed formed during biomass bales combustion in cigar burners. Data collected during the course of research investigation were used to develop a detailed CFD model of straw bales combustion in cigar burners. (C) 2012 Elsevier Ltd. All rights reserved.",
journal = "Energy",
title = "Experimental determination thermo physical characteristics of balled biomass",
volume = "45",
number = "1",
pages = "350-357",
doi = "10.1016/j.energy.2012.02.063"
}

Erić, A., Dakić, D. V., Nemoda, S., Komatina, M.,& Repić, B.. (2012). Experimental determination thermo physical characteristics of balled biomass. in Energy, 45(1), 350-357.
https://doi.org/10.1016/j.energy.2012.02.063

Erić A, Dakić DV, Nemoda S, Komatina M, Repić B. Experimental determination thermo physical characteristics of balled biomass. in Energy. 2012;45(1):350-357.
doi:10.1016/j.energy.2012.02.063 .

Erić, Aleksandar, Dakić, Dragoljub V., Nemoda, Stevan, Komatina, Mirko, Repić, Branislav, "Experimental determination thermo physical characteristics of balled biomass" in Energy, 45, no. 1 (2012):350-357,
https://doi.org/10.1016/j.energy.2012.02.063 . .