33 research outputs found
Multi-fluid model predictions of gas-liquid two-phase flows in vertical tubes
Razvijen je potpun, stabilan, jednodimenzioni viÅ”efluidni model za predviÄanje dvofaznog strujanja u vertikalnim cevima. Model je zasnovan na bilansima održanja mase, koliÄine kretanja i energije, koji su primenjeni na svaku fluidnu struju koja je prisutna u posmatranom obliku dvofaznog strujanja, kao i na odgovarajuÄim konstitutivnim korelacijama za odreÄivanje transportnih procesa na razdelnim povrÅ”inama izmeÄu faza. Bilansne jednaÄine za stacionarno stanje su transformisane u oblik pogodan za direktnu primenu numeriÄke metode za integraciju sistema obiÄnih diferencijalnih jednaÄina. Simulirani su termohidrauliÄki procesi duž celog isparivaÄkog kanala, poÄevÅ”i od strujanja i zagrevanja pothlaÄene teÄnosti na ulazu u strujni kanal pa do zasuÅ”enja teÄnog filma i pojave maglenog toka sa kapima ukljuÄenim u gasnu fazu na kraju kanala. TakoÄe, model je testiran i za uslove nekoliko parcijalnih efekata dvofaznog strujanja.A consistent one-dimensional multi-fluid model is developed for the prediction of two-phase flows in vertical pipes. The model is based on the mass, momentum and energy balance equations for every fluid stream involved in the observed two-phase flow pattern, and corresponding closure laws for interface transfer processes. The steady-state balance equations are transformed in a form suitable for a direct application of the numerical integration method for the system of ordinary differential equations. Thermal-hydraulic processes along the whole length of the boiling channel are simulated, from the flow and heating of sub cooled liquid at the flow channel inlet, and up to the liquid film dry out and gas entrained droplets mist flow at the outlet. Also, the model is tested against several partial effects of two-phase flow
Numerical simulation of condensation induced water hammer
Razvijen je numeriÄki model za simulaciju i analizu hidrauliÄkog udara koji je zasnovan na jednodimenzionalnom homogenom modelu dvofaznog strujanja praÄenju razdelne povrÅ”ine stuba teÄnosti i parnog mehura i modeliranju direktne kondenzacije pare na pothlaÄenoj teÄnosti. Sistem bilansnih jednaÄina je reÅ”en primenom metode karakteristika. Integracija je vrÅ”ena duž tri karakteristiÄna pravca: dva pravca odreÄena su pravcem prostiranja talasa pritiska a treÄi prostiranjem fluidnog deliÄa. PraÄenje fluidnog deliÄa i razdelne povrÅ”ine vode i pare izvrÅ”eno je reÅ”avanjem energetske jednaÄine u prostoru sa taÄnoÅ”Äu treÄeg reda. KoliÄina toplote koju para preda teÄnosti pri kondenzaciji odreÄena je integracijom povrÅ”inskog toplotnog fluksa po razdelnoj povrÅ”ini parne i teÄne faze na mestu kontakta pare i pothlaÄene teÄnosti. Model je primenjen na simulaciju i analizu hidrauliÄkog udara izazvanog u nekoliko eksperimentalih aparatura.A numerical model for the simulation and analysis of the water hammer in the pipe two-phase flow is developed. The modeling is based on one-dimensional homogeneous model of two-phase flow, tracking of the interface between steam volume and water column and modeling of the direct condensation of steam on sub cooled liquid. The mass, momentum and energy conservation equations are solved by the method of characteristics. For these three equations, there are three characteristic directions: two of them are determined by the pressure wave propagation and the third one by the fluid particle propagation. The fluid particle and the steam-water interface tracking are obtained through the energy conservation equation solving in space, with the accuracy of the third degree. The value of thermodynamic quality is used to determine whether the observed computational region is filled with water, two-phase mixture or steam. The term in the energy conservation equation, which contains information about the heat exchanged between steam and liquid phase through condensation, is determined by integration of superficial heat flux over steam-water interface. The model is applied to the simulation and analysis of the air-water interface propagation in the experimental apparatus of oscillating manometer and the condensation induced water hammer in a vertical pipe for draining of steam into the pool filled with sub cooled water
Numerical simulation of condensation induced water hammer
Razvijen je numeriÄki model za simulaciju i analizu hidrauliÄkog udara koji je zasnovan na jednodimenzionalnom homogenom modelu dvofaznog strujanja praÄenju razdelne povrÅ”ine stuba teÄnosti i parnog mehura i modeliranju direktne kondenzacije pare na pothlaÄenoj teÄnosti. Sistem bilansnih jednaÄina je reÅ”en primenom metode karakteristika. Integracija je vrÅ”ena duž tri karakteristiÄna pravca: dva pravca odreÄena su pravcem prostiranja talasa pritiska a treÄi prostiranjem fluidnog deliÄa. PraÄenje fluidnog deliÄa i razdelne povrÅ”ine vode i pare izvrÅ”eno je reÅ”avanjem energetske jednaÄine u prostoru sa taÄnoÅ”Äu treÄeg reda. KoliÄina toplote koju para preda teÄnosti pri kondenzaciji odreÄena je integracijom povrÅ”inskog toplotnog fluksa po razdelnoj povrÅ”ini parne i teÄne faze na mestu kontakta pare i pothlaÄene teÄnosti. Model je primenjen na simulaciju i analizu hidrauliÄkog udara izazvanog u nekoliko eksperimentalih aparatura.A numerical model for the simulation and analysis of the water hammer in the pipe two-phase flow is developed. The modeling is based on one-dimensional homogeneous model of two-phase flow, tracking of the interface between steam volume and water column and modeling of the direct condensation of steam on sub cooled liquid. The mass, momentum and energy conservation equations are solved by the method of characteristics. For these three equations, there are three characteristic directions: two of them are determined by the pressure wave propagation and the third one by the fluid particle propagation. The fluid particle and the steam-water interface tracking are obtained through the energy conservation equation solving in space, with the accuracy of the third degree. The value of thermodynamic quality is used to determine whether the observed computational region is filled with water, two-phase mixture or steam. The term in the energy conservation equation, which contains information about the heat exchanged between steam and liquid phase through condensation, is determined by integration of superficial heat flux over steam-water interface. The model is applied to the simulation and analysis of the air-water interface propagation in the experimental apparatus of oscillating manometer and the condensation induced water hammer in a vertical pipe for draining of steam into the pool filled with sub cooled water
Multi-fluid model predictions of gas-liquid two-phase flows in vertical tubes
Razvijen je potpun, stabilan, jednodimenzioni viÅ”efluidni model za predviÄanje dvofaznog strujanja u vertikalnim cevima. Model je zasnovan na bilansima održanja mase, koliÄine kretanja i energije, koji su primenjeni na svaku fluidnu struju koja je prisutna u posmatranom obliku dvofaznog strujanja, kao i na odgovarajuÄim konstitutivnim korelacijama za odreÄivanje transportnih procesa na razdelnim povrÅ”inama izmeÄu faza. Bilansne jednaÄine za stacionarno stanje su transformisane u oblik pogodan za direktnu primenu numeriÄke metode za integraciju sistema obiÄnih diferencijalnih jednaÄina. Simulirani su termohidrauliÄki procesi duž celog isparivaÄkog kanala, poÄevÅ”i od strujanja i zagrevanja pothlaÄene teÄnosti na ulazu u strujni kanal pa do zasuÅ”enja teÄnog filma i pojave maglenog toka sa kapima ukljuÄenim u gasnu fazu na kraju kanala. TakoÄe, model je testiran i za uslove nekoliko parcijalnih efekata dvofaznog strujanja.A consistent one-dimensional multi-fluid model is developed for the prediction of two-phase flows in vertical pipes. The model is based on the mass, momentum and energy balance equations for every fluid stream involved in the observed two-phase flow pattern, and corresponding closure laws for interface transfer processes. The steady-state balance equations are transformed in a form suitable for a direct application of the numerical integration method for the system of ordinary differential equations. Thermal-hydraulic processes along the whole length of the boiling channel are simulated, from the flow and heating of sub cooled liquid at the flow channel inlet, and up to the liquid film dry out and gas entrained droplets mist flow at the outlet. Also, the model is tested against several partial effects of two-phase flow
PredviÄanje dvofaznog strujanja sa generacijom pare oko cevi u snopu u isparivaÄima i generatorima pare
U hemijskoj industriji i energetici se koriste isparivaÄi i
generatori pare sa kljuÄanjem na spoljaÅ”njoj povrÅ”ini
cevi koje formiraju cevni snop. Pri kljuÄanju fluida
deŔavaju se složeni procesi prenosa toplote i mase koji
odreÄuju polje brzina obe faze, polje pritiska i raspored zapreminskog
udela parne faze u ovim komponentama. Velike
vrednosti zapreminskog udela pare mogu da izazovu krizu
razmene toplote, koja se javlja u promenljivim ili prelaznim
režimima kada je deo cevnog snopa okružen samo parnom
fazom. TakoÄe, veliki protok dvofazne meÅ”avine može da
dovede do vibracija cevi isparivaÄa ili generatora pare, dok
recirkulacija teÄnosti može da izazove taloženje primesa
u pojedinim delovima generatora. Model predstavljen u
ovom radu je podrŔka projektovanju i analizama rada generatora
pare i isparivaÄa. Zasnovan je na reÅ”avanju bilansnih
jednaÄina za svaku od faza u dvofaznom toku, uz primenu
odgovarajuÄih konstitutivnih korelacija i omoguÄava
izraÄunavanje brzinskog polja, polja pritiska i zapreminskog
udela pare oko horizontalnog ili vertikalnog cevnog
snopa, kao i predviÄanje položaja dvofazne meÅ”avin
Numerical simulation of dynamic loads at the steam pipe line of the thermal power plant 'Nikola Tesla Bā
OdreÄivanje dinamiÄkih sila kojima nestacionarna struja fluida deluje na cevovod je neophodno u cilju sagledavanja maksimalnih naprezanja koja deluju na strukturu, spojeve i oslonce, odnosno u cilju dobijanja podloga za projektovanje ovih elemenata na maksimalna dinamiÄka naprezanja. U radu su prikazani metodologija i rezultati raÄunarske simulacije nestacionarnih gasodinamiÄkih sila koje deluju na parovod tople meÄupregrejane pare termoelektrane āNikola Tesla Bā. Nestacionarne gasodinamiÄke sile nastaju usled nestacionarnog strujanja radnog fluida pri delovanju sigurnosno-zaÅ”titnih sistema. Zatvaranje pregradnih ventila ispred tur bine srednjeg pritiska zaustavlja protok pare i dovodi do porasta pritiska ispred pregradnih ventila, i prostiranja i superponiranja talasa pritiska duž parovoda, Å”to izaziva dopunska dinamiÄka optereÄenja parovoda. OdreÄivanje dinamiÄkih fluidnih sila se vrÅ”i zajedno sa simulacijom nestacionarnog strujanja pare. Simulacija strujanja i odreÄivanje fluidnih dinamiÄkih sila su sprovedeni pomoÄu raÄunarskog programa TEA razvijenog na MaÅ”inskom fakultetu u Beogradu. Dobijeni rezultati su koriÅ”Äeni u okviru revizije inostranog projekta rekonstrukcije (zamene) parovoda meÄupregrejane pare na termoelektrani āNikola Tesla Bā. Rezultati proraÄuna dobijeni programom TEA su uporeÄeni sa rezultatima inostranog raÄunarskog programa SHOCK i dobijeno je prihvatljivo slaganje.Prediction of the transient fluid dynamic forces that act on the pipe line structure, junctions and supports are important in order to predict the maximum design loads. The paper presents the methodology and results of the fluid dynamic forces prediction for the reheated steam pipe line at the Thermal Power Plant āNikola Tesla Bā. The dynamic forces are induced by fluid transient flow caused by the action of the plant safety system. Closure of the isolation valves in front of the intermediate pressure turbine stops the steam flow and leads to the in crease of pres sure in front of the isolation valves, pressure waves propagation and super position along the pipe line, which cause additional dynamic loading of the pipe line structure. Prediction of the fluid dynamic forces is performed simultaneously with the simulation of the transient fluid flow. Transient simulation of fluid flow and calculation of fluid-dynamic forces are performed with the computer code TEA (Transient Evaluation Analyses), which is developed at the Faculty of Mechanical Engineering in Belgrade. Obtained results are used for the review of a foreign project on the reconstruction (replacement) of steam pipeline in Thermal Power Plant āNikola Tesla Bā. Results obtained with the computer code TEA are compared with results of foreign computer code SHOCK. Acceptably agreement is achieved
Numerical simulation of dynamic loads at the steam pipe line of the thermal power plant 'Nikola Tesla Bā
OdreÄivanje dinamiÄkih sila kojima nestacionarna struja fluida deluje na cevovod je neophodno u cilju sagledavanja maksimalnih naprezanja koja deluju na strukturu, spojeve i oslonce, odnosno u cilju dobijanja podloga za projektovanje ovih elemenata na maksimalna dinamiÄka naprezanja. U radu su prikazani metodologija i rezultati raÄunarske simulacije nestacionarnih gasodinamiÄkih sila koje deluju na parovod tople meÄupregrejane pare termoelektrane āNikola Tesla Bā. Nestacionarne gasodinamiÄke sile nastaju usled nestacionarnog strujanja radnog fluida pri delovanju sigurnosno-zaÅ”titnih sistema. Zatvaranje pregradnih ventila ispred tur bine srednjeg pritiska zaustavlja protok pare i dovodi do porasta pritiska ispred pregradnih ventila, i prostiranja i superponiranja talasa pritiska duž parovoda, Å”to izaziva dopunska dinamiÄka optereÄenja parovoda. OdreÄivanje dinamiÄkih fluidnih sila se vrÅ”i zajedno sa simulacijom nestacionarnog strujanja pare. Simulacija strujanja i odreÄivanje fluidnih dinamiÄkih sila su sprovedeni pomoÄu raÄunarskog programa TEA razvijenog na MaÅ”inskom fakultetu u Beogradu. Dobijeni rezultati su koriÅ”Äeni u okviru revizije inostranog projekta rekonstrukcije (zamene) parovoda meÄupregrejane pare na termoelektrani āNikola Tesla Bā. Rezultati proraÄuna dobijeni programom TEA su uporeÄeni sa rezultatima inostranog raÄunarskog programa SHOCK i dobijeno je prihvatljivo slaganje.Prediction of the transient fluid dynamic forces that act on the pipe line structure, junctions and supports are important in order to predict the maximum design loads. The paper presents the methodology and results of the fluid dynamic forces prediction for the reheated steam pipe line at the Thermal Power Plant āNikola Tesla Bā. The dynamic forces are induced by fluid transient flow caused by the action of the plant safety system. Closure of the isolation valves in front of the intermediate pressure turbine stops the steam flow and leads to the in crease of pres sure in front of the isolation valves, pressure waves propagation and super position along the pipe line, which cause additional dynamic loading of the pipe line structure. Prediction of the fluid dynamic forces is performed simultaneously with the simulation of the transient fluid flow. Transient simulation of fluid flow and calculation of fluid-dynamic forces are performed with the computer code TEA (Transient Evaluation Analyses), which is developed at the Faculty of Mechanical Engineering in Belgrade. Obtained results are used for the review of a foreign project on the reconstruction (replacement) of steam pipeline in Thermal Power Plant āNikola Tesla Bā. Results obtained with the computer code TEA are compared with results of foreign computer code SHOCK. Acceptably agreement is achieved
Possible use of hydropower potential of cooling water at the thermal power plant
U radu je prikazana moguÄnost koriÅ”Äenja hidroenergetskog potencijala rashladne vode termoelektrane sa otvorenim sistemom hlaÄenja. Rashladna voda otiÄe gravitaciono do recipijenta - reke, zbog Äega se u periodu nižih vodostaja javlja pad koji je moguÄe iskoristiti u maloj hidoelektrani. Takva hidroelektrana radi sa promenljivim padom i približno konstantnim protokom, i to samo u periodima kada radi i termoelektrana. Koncepcija je prikazana na primeru male hidroelektrane koja Äe koristiti hidroenergetski potencijal rashladne vode TE 'Nikola Tesla B'. OdreÄeni su ekonomski pokazatelji ove hidroelektrane i ocenjeno je poveÄanje profitabilnosti imajuÄi u vidu da postrojenje može biTI ostvareno u okvira Clean Development Mechanism (CDM) projekta, u skladu sa Kjoto protokolom. Dobijeni rezultati pokazuju da je projekat ekonomski prihvatljiv, a moguÄe ga je ostvariti sa standardnim hidroturbinama dostupnim na tržiÅ”tu.Possibility of using hydropower potential of cooling water at the thermal power plant with open cooling system is presented in the paper. Cooling water flows gravitationally to the recipient - the river. In the periods of low water levels additional head occurs which could be used in small hydropower plant. Such a hydropower plant will operate only in periods when thermal power plant operates, with more or less constant flow and head that significantly changes in time. Small hydropower plant that uses cooling water of Thermal Power Plant 'Nikola Tesla B' is presented in the paper. The economic benefits of the HPP are calculated. The increase of profitability is assessed, bearing in mind that the plant would be realized as the Clean Development Mechanism project according to the Kyoto protocol. The obtained results show that the project is economically attractive, and it can be carried out with standard matured solutions of hydro turbines available at the market
MoguÄnost koriÅ”Äenja hidroenergetskog potencijala vode za hlaÄenje termoelektrana
Possibility of using hydropower potential of cooling water at the thermal power plant with open cooling system is presented in the paper. Cooling water flows gravitationally to the recipient - the river. In the periods of low water levels additional head occurs which could be used in small hydropower plant. Such a hydropower plant will operate only in periods when thermal power plant operates, with more or less constant flow and head that significantly changes in time. Small hydropower plant that uses cooling water of Thermal Power Plant 'Nikola Tesla B' is presented in the paper. The economic benefits of the HPP are calculated. The increase of profitability is assessed, bearing in mind that the plant would be realized as the Clean Development Mechanism project according to the Kyoto protocol. The obtained results show that the project is economically attractive, and it can be carried out with standard matured solutions of hydro turbines available at the market.U radu je prikazana moguÄnost koriÅ”Äenja hidroenergetskog potencijala rashladne vode termoelektrane sa otvorenim sistemom hlaÄenja. Rashladna voda otiÄe gravitaciono do recipijenta - reke, zbog Äega se u periodu nižih vodostaja javlja pad koji je moguÄe iskoristiti u maloj hidoelektrani. Takva hidroelektrana radi sa promenljivim padom i približno konstantnim protokom, i to samo u periodima kada radi i termoelektrana. Koncepcija je prikazana na primeru male hidroelektrane koja Äe koristiti hidroenergetski potencijal rashladne vode TE 'Nikola Tesla B'. OdreÄeni su ekonomski pokazatelji ove hidroelektrane i ocenjeno je poveÄanje profitabilnosti imajuÄi u vidu da postrojenje može biTI ostvareno u okvira Clean Development Mechanism (CDM) projekta, u skladu sa Kjoto protokolom. Dobijeni rezultati pokazuju da je projekat ekonomski prihvatljiv, a moguÄe ga je ostvariti sa standardnim hidroturbinama dostupnim na tržiÅ”tu
Possible use of hydropower potential of cooling water at the thermal power plant
U radu je prikazana moguÄnost koriÅ”Äenja hidroenergetskog potencijala rashladne vode termoelektrane sa otvorenim sistemom hlaÄenja. Rashladna voda otiÄe gravitaciono do recipijenta - reke, zbog Äega se u periodu nižih vodostaja javlja pad koji je moguÄe iskoristiti u maloj hidoelektrani. Takva hidroelektrana radi sa promenljivim padom i približno konstantnim protokom, i to samo u periodima kada radi i termoelektrana. Koncepcija je prikazana na primeru male hidroelektrane koja Äe koristiti hidroenergetski potencijal rashladne vode TE 'Nikola Tesla B'. OdreÄeni su ekonomski pokazatelji ove hidroelektrane i ocenjeno je poveÄanje profitabilnosti imajuÄi u vidu da postrojenje može biTI ostvareno u okvira Clean Development Mechanism (CDM) projekta, u skladu sa Kjoto protokolom. Dobijeni rezultati pokazuju da je projekat ekonomski prihvatljiv, a moguÄe ga je ostvariti sa standardnim hidroturbinama dostupnim na tržiÅ”tu.Possibility of using hydropower potential of cooling water at the thermal power plant with open cooling system is presented in the paper. Cooling water flows gravitationally to the recipient - the river. In the periods of low water levels additional head occurs which could be used in small hydropower plant. Such a hydropower plant will operate only in periods when thermal power plant operates, with more or less constant flow and head that significantly changes in time. Small hydropower plant that uses cooling water of Thermal Power Plant 'Nikola Tesla B' is presented in the paper. The economic benefits of the HPP are calculated. The increase of profitability is assessed, bearing in mind that the plant would be realized as the Clean Development Mechanism project according to the Kyoto protocol. The obtained results show that the project is economically attractive, and it can be carried out with standard matured solutions of hydro turbines available at the market