TY  - CONF
AU  - Ilić, Milica
AU  - Stevanović, Vladimir
AU  - Petrović, Milan M.
AU  - Milivojević, Sanja
PY  - 2023
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/7090
AB  - This paper deals with current status and possibilities for feasible improvement of the flexibility of power generation fleet consisting of aged coal-fired power plants and hydro power plants. The analyses are done by use of well-established deterministic metrics - the normalized flexibility indicator for each power unit is evaluated accounting for ramp up and ramp down power rates as well as the unit operating range. The method is applied to the case of the Electric Power Industry of Serbia (EPS). As expected, hydro power units are highly flexible with normalized flexibility indicator reaching the values as high as 0.78 (on the scale from 0 to 1). The units in power plants fired with lignite are of low flexibility - especially the units with the greatest power where the flexibility indicator is well below 0.2. This issue can represent a serious constraint for operation of these units in conditions of variable demand and future implementation of renewable energy sources with intermittent power generation. 
In units of lignite fired power plants the operating range (formulated as difference between maximal and minimal net electric power) is a stronger limitation than the value of ramp up / down rate. Therefore, the efforts for flexibility enhancement focus on lowering of minimal or increase of unit maximal power. In literature various technical measures are considered for this purpose. Despite their undoubtably positive impact, some of these measures (for example, implementation of additional boiler or replacement of thick-wall by thin-wall parts) would represent such a drastic surgery for the aged lignite fired power fleet that they cannot be considered as feasible. For that reason, we analyse sophisticated technical measures which contribute to flexibility increase, but do not require too high retrofitting costs. The solutions are based on (i) advanced operational procedures for feedwater redistribution (ii) installation of additional economizers for recovery of flue gas heat and (iii) implementation of steam accumulators.
PB  - Beograd : Društvo termičara Srbije
C3  - International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. november 2023.
T1  - Flexibility of power generation and possibilities for feasible upgrades of coal power plants: a case of the Electric Power Industry of Serbia
EP  - 435
SP  - 426
UR  - https://hdl.handle.net/21.15107/rcub_machinery_7090
ER  - 

@conference{
author = "Ilić, Milica and Stevanović, Vladimir and Petrović, Milan M. and Milivojević, Sanja",
year = "2023",
abstract = "This paper deals with current status and possibilities for feasible improvement of the flexibility of power generation fleet consisting of aged coal-fired power plants and hydro power plants. The analyses are done by use of well-established deterministic metrics - the normalized flexibility indicator for each power unit is evaluated accounting for ramp up and ramp down power rates as well as the unit operating range. The method is applied to the case of the Electric Power Industry of Serbia (EPS). As expected, hydro power units are highly flexible with normalized flexibility indicator reaching the values as high as 0.78 (on the scale from 0 to 1). The units in power plants fired with lignite are of low flexibility - especially the units with the greatest power where the flexibility indicator is well below 0.2. This issue can represent a serious constraint for operation of these units in conditions of variable demand and future implementation of renewable energy sources with intermittent power generation. 
In units of lignite fired power plants the operating range (formulated as difference between maximal and minimal net electric power) is a stronger limitation than the value of ramp up / down rate. Therefore, the efforts for flexibility enhancement focus on lowering of minimal or increase of unit maximal power. In literature various technical measures are considered for this purpose. Despite their undoubtably positive impact, some of these measures (for example, implementation of additional boiler or replacement of thick-wall by thin-wall parts) would represent such a drastic surgery for the aged lignite fired power fleet that they cannot be considered as feasible. For that reason, we analyse sophisticated technical measures which contribute to flexibility increase, but do not require too high retrofitting costs. The solutions are based on (i) advanced operational procedures for feedwater redistribution (ii) installation of additional economizers for recovery of flue gas heat and (iii) implementation of steam accumulators.",
publisher = "Beograd : Društvo termičara Srbije",
journal = "International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. november 2023.",
title = "Flexibility of power generation and possibilities for feasible upgrades of coal power plants: a case of the Electric Power Industry of Serbia",
pages = "435-426",
url = "https://hdl.handle.net/21.15107/rcub_machinery_7090"
}

Ilić, M., Stevanović, V., Petrović, M. M.,& Milivojević, S.. (2023). Flexibility of power generation and possibilities for feasible upgrades of coal power plants: a case of the Electric Power Industry of Serbia. in International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. november 2023.
Beograd : Društvo termičara Srbije., 426-435.
https://hdl.handle.net/21.15107/rcub_machinery_7090

Ilić M, Stevanović V, Petrović MM, Milivojević S. Flexibility of power generation and possibilities for feasible upgrades of coal power plants: a case of the Electric Power Industry of Serbia. in International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. november 2023.. 2023;:426-435.
https://hdl.handle.net/21.15107/rcub_machinery_7090 .

Ilić, Milica, Stevanović, Vladimir, Petrović, Milan M., Milivojević, Sanja, "Flexibility of power generation and possibilities for feasible upgrades of coal power plants: a case of the Electric Power Industry of Serbia" in International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. november 2023. (2023):426-435,
https://hdl.handle.net/21.15107/rcub_machinery_7090 .

TY  - CONF
AU  - Petrović, Milan M.
AU  - Stevanović, Vladimir
AU  - Milivojević, Sanja
AU  - Ilić, Milica
PY  - 2023
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/7091
AB  - Potential for the waste heat utilization in coal-fired thermal power plants that are in operation for a long period is reflected in an increased temperature of the flue gas at the exit of the regenerative air heater. After a long period of operation, the flue gas temperature exceeds the design value and is around 170 °C. In thermal power plants where a flue gas desulphurization plant has been built, the flue gas must be cooled at the absorber inlet to approximately 70 °C due to the efficiency of the desulphurization process, and thus the waste heat is irreversibly lost to the environment. Given the large temperature difference between the flue gas temperature at the boiler outlet and the temperature at the absorber inlet, as well as the large flue gas flow, there is a significant potential for the utilization of this waste heat. This potential can be used to heat the condensate from the steam power plant condensate line, where due to reduced steam extractions from the low-pressure turbine, the unchanged steam unit power is maintained with the lower fresh steam flow rate or the production of electricity increases without additional fuel consumption. The paper presents a technical solution for the utilization of waste heat in a low-pressure economizer at the 350 MWe lignite-fired thermal power plant. The energy balancing of the steam unit with the installed low-pressure economizer was performed and the increase in net unit efficiency was determined by applying the described solution in relation to the design conditions. It is shown that the net efficiency of the steam unit increases by 1.06 percentage points. About 73 GWh of electricity is produced by the flue gas waste heat utilization, which gives an annual reduction in coal consumption of approximately 98,000 tons, as well as an annual reduction in CO2 emissions of approximately 72,000 tons.
PB  - Beograd : Društvo termičara Srbije
C3  - International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. November 2023.
T1  - UTILIZATION OF THE FLUE GAS WASTE HEAT BY THE LOW-PRESSURE ECONOMIZER AT 350 MWE LIGNITE-FIRED POWER PLANT
EP  - 680
SP  - 675
UR  - https://hdl.handle.net/21.15107/rcub_machinery_7091
ER  - 

@conference{
author = "Petrović, Milan M. and Stevanović, Vladimir and Milivojević, Sanja and Ilić, Milica",
year = "2023",
abstract = "Potential for the waste heat utilization in coal-fired thermal power plants that are in operation for a long period is reflected in an increased temperature of the flue gas at the exit of the regenerative air heater. After a long period of operation, the flue gas temperature exceeds the design value and is around 170 °C. In thermal power plants where a flue gas desulphurization plant has been built, the flue gas must be cooled at the absorber inlet to approximately 70 °C due to the efficiency of the desulphurization process, and thus the waste heat is irreversibly lost to the environment. Given the large temperature difference between the flue gas temperature at the boiler outlet and the temperature at the absorber inlet, as well as the large flue gas flow, there is a significant potential for the utilization of this waste heat. This potential can be used to heat the condensate from the steam power plant condensate line, where due to reduced steam extractions from the low-pressure turbine, the unchanged steam unit power is maintained with the lower fresh steam flow rate or the production of electricity increases without additional fuel consumption. The paper presents a technical solution for the utilization of waste heat in a low-pressure economizer at the 350 MWe lignite-fired thermal power plant. The energy balancing of the steam unit with the installed low-pressure economizer was performed and the increase in net unit efficiency was determined by applying the described solution in relation to the design conditions. It is shown that the net efficiency of the steam unit increases by 1.06 percentage points. About 73 GWh of electricity is produced by the flue gas waste heat utilization, which gives an annual reduction in coal consumption of approximately 98,000 tons, as well as an annual reduction in CO2 emissions of approximately 72,000 tons.",
publisher = "Beograd : Društvo termičara Srbije",
journal = "International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. November 2023.",
title = "UTILIZATION OF THE FLUE GAS WASTE HEAT BY THE LOW-PRESSURE ECONOMIZER AT 350 MWE LIGNITE-FIRED POWER PLANT",
pages = "680-675",
url = "https://hdl.handle.net/21.15107/rcub_machinery_7091"
}

Petrović, M. M., Stevanović, V., Milivojević, S.,& Ilić, M.. (2023). UTILIZATION OF THE FLUE GAS WASTE HEAT BY THE LOW-PRESSURE ECONOMIZER AT 350 MWE LIGNITE-FIRED POWER PLANT. in International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. November 2023.
Beograd : Društvo termičara Srbije., 675-680.
https://hdl.handle.net/21.15107/rcub_machinery_7091

Petrović MM, Stevanović V, Milivojević S, Ilić M. UTILIZATION OF THE FLUE GAS WASTE HEAT BY THE LOW-PRESSURE ECONOMIZER AT 350 MWE LIGNITE-FIRED POWER PLANT. in International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. November 2023.. 2023;:675-680.
https://hdl.handle.net/21.15107/rcub_machinery_7091 .

Petrović, Milan M., Stevanović, Vladimir, Milivojević, Sanja, Ilić, Milica, "UTILIZATION OF THE FLUE GAS WASTE HEAT BY THE LOW-PRESSURE ECONOMIZER AT 350 MWE LIGNITE-FIRED POWER PLANT" in International Conference "Power Plants 2023", Zlatibor, Serbia, 8-10. November 2023. (2023):675-680,
https://hdl.handle.net/21.15107/rcub_machinery_7091 .

TY  - JOUR
AU  - Stevanović, Vladimir
AU  - Petrović, Milan M.
AU  - Ćućuz, Stojan
AU  - Milivojević, Sanja
AU  - Ilić, Milica
PY  - 2023
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/7642
AB  - Оil lubricates the contact of the orbiting and stationary scroll in the refrigerant scroll compressor, while the sealing between the scrolls is achieved by the refrigerant vapour pressure in the sealed back pressure chamber. The back pressure should be adjusted by the refrigerant-oil two-phase flow from the oil separator at the compressor discharge to the back pressure chamber and the refrigerant-oil flow from the back pressure chamber to the compressor suction side. Both flows are conducted through connecting tubes with corresponding high-pressure and low-pressure nozzles of small diameters. Models for the prediction of refrigerant-oil critical and subcritical flows through nozzles are developed and applied for the prediction of back pressure. The models are original since the slip between oil and refrigerant as well as the refrigerant solubility in oil are taken into account. The critical flow model is validated against experimental data available in the literature. The back pressure is predicted by equating the mass flow rates of refrigerant and oil two-phase mixtures through the high and low-pressure nozzles. The results show that the critical flow takes place through the high-pressure nozzle, while the subcritical flow through the low-pressure nozzle can also exist in cases with small pressure difference between the back pressure chamber and the compressor suction side. The refrigerant solubility in oil has a small influence on the critical and subcritical refrigerant-oil mixture mass flow rates, while the influence on the back pressure is more pronounced.
PB  - MDPI, Basel, Switzerland
T2  - Processes
T1  - Numerical Prediction of Refrigerant-Oil Two-Phase Flow from The Scroll Compressor Discharge to the Suction Side via the Back Pressure Chamber
IS  - 1
SP  - 6
VL  - 12
DO  - 10.3390/pr12010006
ER  - 

@article{
author = "Stevanović, Vladimir and Petrović, Milan M. and Ćućuz, Stojan and Milivojević, Sanja and Ilić, Milica",
year = "2023",
abstract = "Оil lubricates the contact of the orbiting and stationary scroll in the refrigerant scroll compressor, while the sealing between the scrolls is achieved by the refrigerant vapour pressure in the sealed back pressure chamber. The back pressure should be adjusted by the refrigerant-oil two-phase flow from the oil separator at the compressor discharge to the back pressure chamber and the refrigerant-oil flow from the back pressure chamber to the compressor suction side. Both flows are conducted through connecting tubes with corresponding high-pressure and low-pressure nozzles of small diameters. Models for the prediction of refrigerant-oil critical and subcritical flows through nozzles are developed and applied for the prediction of back pressure. The models are original since the slip between oil and refrigerant as well as the refrigerant solubility in oil are taken into account. The critical flow model is validated against experimental data available in the literature. The back pressure is predicted by equating the mass flow rates of refrigerant and oil two-phase mixtures through the high and low-pressure nozzles. The results show that the critical flow takes place through the high-pressure nozzle, while the subcritical flow through the low-pressure nozzle can also exist in cases with small pressure difference between the back pressure chamber and the compressor suction side. The refrigerant solubility in oil has a small influence on the critical and subcritical refrigerant-oil mixture mass flow rates, while the influence on the back pressure is more pronounced.",
publisher = "MDPI, Basel, Switzerland",
journal = "Processes",
title = "Numerical Prediction of Refrigerant-Oil Two-Phase Flow from The Scroll Compressor Discharge to the Suction Side via the Back Pressure Chamber",
number = "1",
pages = "6",
volume = "12",
doi = "10.3390/pr12010006"
}

Stevanović, V., Petrović, M. M., Ćućuz, S., Milivojević, S.,& Ilić, M.. (2023). Numerical Prediction of Refrigerant-Oil Two-Phase Flow from The Scroll Compressor Discharge to the Suction Side via the Back Pressure Chamber. in Processes
MDPI, Basel, Switzerland., 12(1), 6.
https://doi.org/10.3390/pr12010006

Stevanović V, Petrović MM, Ćućuz S, Milivojević S, Ilić M. Numerical Prediction of Refrigerant-Oil Two-Phase Flow from The Scroll Compressor Discharge to the Suction Side via the Back Pressure Chamber. in Processes. 2023;12(1):6.
doi:10.3390/pr12010006 .

Stevanović, Vladimir, Petrović, Milan M., Ćućuz, Stojan, Milivojević, Sanja, Ilić, Milica, "Numerical Prediction of Refrigerant-Oil Two-Phase Flow from The Scroll Compressor Discharge to the Suction Side via the Back Pressure Chamber" in Processes, 12, no. 1 (2023):6,
https://doi.org/10.3390/pr12010006 . .

TY  - CONF
AU  - Ilić, Milica
AU  - Stevović, Ivan
AU  - Stevović, Svetlana
PY  - 2014
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/7037
AB  - The main objective for the conducted research presented in this paper was to quantify, analyze 
reversibility of the algal bloom process and present changes in water quality parameters in the 
function of time, depth and temperature in reservoirs. The motive is to meet the water quality 
criteria for lake water intended for water supply at all times. The example of Ćelije reservoir 
was used to depict the correlation between the protection regime in sanitary zones and 
reservoir water quality over time. Kruševac Town is supplied with drinking water from the 
reservoir subject to the research, i.e. from its 41·106m
3
of lake water, after treatment in a 
water treatment plant. The research covered water analyses in the period after algal bloom, as 
well, with the goal to quantify the level of autoregeneration. The lake eutrophication process, 
as a consequence of multiple pollution, i.e. import of nitrogen and phosphorous compounds, 
resulted in domination of Cyanobacteria or, in fact, permanent blooming. The conclusion is 
that continuous preservation of water quality in water supply reservoirs may be achieved only 
with imperative regular monitoring and observation of strictly defined preventive measures 
for all the sanitary protection zones.
PB  - Faculty of Mechanical Engineering and Naval Architecture, Zagreb
C3  - 1st South East European Conference on Sustainable Development of Energy, Water and Environment Systems, (SDEWES Ohrid)
T1  - Management of water quality in reservoirs in correlation with environment
UR  - https://hdl.handle.net/21.15107/rcub_machinery_7037
ER  - 

@conference{
author = "Ilić, Milica and Stevović, Ivan and Stevović, Svetlana",
year = "2014",
abstract = "The main objective for the conducted research presented in this paper was to quantify, analyze 
reversibility of the algal bloom process and present changes in water quality parameters in the 
function of time, depth and temperature in reservoirs. The motive is to meet the water quality 
criteria for lake water intended for water supply at all times. The example of Ćelije reservoir 
was used to depict the correlation between the protection regime in sanitary zones and 
reservoir water quality over time. Kruševac Town is supplied with drinking water from the 
reservoir subject to the research, i.e. from its 41·106m
3
of lake water, after treatment in a 
water treatment plant. The research covered water analyses in the period after algal bloom, as 
well, with the goal to quantify the level of autoregeneration. The lake eutrophication process, 
as a consequence of multiple pollution, i.e. import of nitrogen and phosphorous compounds, 
resulted in domination of Cyanobacteria or, in fact, permanent blooming. The conclusion is 
that continuous preservation of water quality in water supply reservoirs may be achieved only 
with imperative regular monitoring and observation of strictly defined preventive measures 
for all the sanitary protection zones.",
publisher = "Faculty of Mechanical Engineering and Naval Architecture, Zagreb",
journal = "1st South East European Conference on Sustainable Development of Energy, Water and Environment Systems, (SDEWES Ohrid)",
title = "Management of water quality in reservoirs in correlation with environment",
url = "https://hdl.handle.net/21.15107/rcub_machinery_7037"
}

Ilić, M., Stevović, I.,& Stevović, S.. (2014). Management of water quality in reservoirs in correlation with environment. in 1st South East European Conference on Sustainable Development of Energy, Water and Environment Systems, (SDEWES Ohrid)
Faculty of Mechanical Engineering and Naval Architecture, Zagreb..
https://hdl.handle.net/21.15107/rcub_machinery_7037

Ilić M, Stevović I, Stevović S. Management of water quality in reservoirs in correlation with environment. in 1st South East European Conference on Sustainable Development of Energy, Water and Environment Systems, (SDEWES Ohrid). 2014;.
https://hdl.handle.net/21.15107/rcub_machinery_7037 .

Ilić, Milica, Stevović, Ivan, Stevović, Svetlana, "Management of water quality in reservoirs in correlation with environment" in 1st South East European Conference on Sustainable Development of Energy, Water and Environment Systems, (SDEWES Ohrid) (2014),
https://hdl.handle.net/21.15107/rcub_machinery_7037 .