https://aseestant.ceon.rs/index.php/terteh <p class="MsoNormal"><span lang="EN-US">At the first gathering of thermal experts of Yugoslavia more than fifty years ago, two important decisions were made - to establish the Society of Thermal Engineers of Yugoslavia and to launch the professional journal of thermal engineers "Termotehnika".</span></p> <p class="MsoNormal"><span lang="EN-US">The established Yugoslav Society of Thermal Engineers has successfully gathered thermal engineers at its symposia throughout Yugoslavia for years.</span></p> <p class="MsoNormal"><span lang="EN-US">Today, in a changed environment, the Society of Thermal Engineers brings together the thermal engineers of Serbia.</span></p> <p class="MsoNormal"><span lang="EN-US">The journal "Termotehnika", initiated in 1974, whose first editor-in-chief was professor Milan Vesović from the Faculty of Mechanical Engineering in Belgrade, and who was succeeded by Dr. Ljubomir Jovanović, scientific adviser from the Laboratory for Thermal Engineering and Energy, has a great merit in the Society's activities, of the Institute for Nuclear Sciences "Vinca" until his untimely death.</span></p> <p class="MsoNormal"><span lang="EN-US">The journal was conceived as a newsletter of the Society with the publication of papers from the symposiums, but it soon began to publish scientific and professional papers in the field of heat and mass transfer from all republics of the SFRY.</span></p> <p class="MsoNormal"><span lang="EN-US">Most of the works were published from Serbia and Slovenia.</span></p> <p class="MsoNormal"><span lang="EN-US">Since 1994, an issue of "Termotehnika" has been printed in English, which since 1997 has been published as a special journal called "Thermal Science", set up according to all the criteria of international journals, with an international editor and international review of papers.</span></p> <p class="MsoNormal"><span lang="EN-US">However, something is changing, there is interest in publishing works from neighboring countries in the same or similar language area. This directs us to persevere in further exposure. Tired older members of the Society and editorial staff are being replaced by younger ones who will give a new impulse both in maintaining quality and in quantity.</span></p> <p class="MsoNormal"><span lang="EN-US">However, the main driving force and desire to continue publishing the journal are the papers.</span></p> <p class="MsoNormal"><span lang="EN-US">Without them, the journal would have stop publishing a long time ago.</span></p> <p class="MsoNormal"><span lang="EN-US">If one should be singled out, it would be the Laboratory for Thermal Engineering and Energy of the "Vinca" Institute, which at times was the only financier, and the printing office of the "Vinca" Institute, which, with great efforts, managed to print the journal in the face of general poverty and difficulties in procuring paper and other materials.</span></p> <p class="MsoNormal"><span lang="EN-US">Celebrating the fiftieth anniversary of the publication of the journal "Termotehnika", we must be satisfied with the results achieved in the difficult years behind us, with the wish that the road ahead will be less thorny and that finances will not be a limiting factor in maintaining the quality and regularity of publication in full circulation.</span></p> <p class="MsoNormal"><span lang="EN-US">&nbsp;</span></p> <p class="MsoNormal"><span lang="EN-US">Editorial Board, </span></p> <p>&nbsp;</p> <p class="MsoNormal"><span lang="EN-US">"Termotehnika"</span></p> sr-RS@latin deki@vinca.rs (Dejan Cvetinović) deki@vinca.rs (Dejan Cvetinović) Fri, 29 Jun 2018 00:00:00 +0200 OJS 3.1.2.0 http://blogs.law.harvard.edu/tech/rss 60 https://aseestant.ceon.rs/index.php/terteh/article/view/17757 U radu su za karakteristične grupe cevnih razmenjivača toplote sa omotačem uz prisustvo pregrada, određene optimalne brzine fluida kroz cev i omotač, polazeći od funkcije ukupnih troškova koji obuhvataju fiksne troškove i troškove energije, odnosno snage za potiskivanje fluida. Komponente funkcije optimizacije izražene su u pogodnim jedinicama što je omogućilo uspostavljanje matematičkog modela u kome figurišu obe brzine fluida koje se optimiziraju. U ovu svrhu korišćene su matematičke transformacije odgovarajućih termodinamičkih i hidrauličkih relacija. Optimalna vrednost brzina fluida dobijena je minimizacijom složene funkcije ukupnih troškova pri čemu su korišćene teoreme diferencijalnog računa koje se odnose na funkcije sa dve promenljive. Dobijena funkcija, kao dvodimenzionalni problem, ispitana je detaljno postupkom matematičke analize. Pri ovome se vodilo računa i o ograničenjima pojedinih parametara. Izvedene relacije predstavljaju opšti model za rešavanje postavljenog problema. Parcijalnim diferenciranjem funkcije optimizacije dobijen je složeni sistem jednačina koji se može rešiti numeričkom matematičkom metodom uz podršku računarskog programa, s obzirom da se parametri koji se optimiziraju ne mogu izraziti eksplicitno. Radi efikasnijeg dobijanja rešenja, pored analitičkog korišćen je i grafički postupak. Ovakav tehno-ekonomski pristup postavljenom problemu, zbog uvedenih dopunskih uslova, zahtevao je iterativno određivanje parametara neophodnih za projektovanje. Razlog ovome je taj što je morao biti zadovoljen veći broj jednačina uz poštovanje određenih ograničenja. Slavko Smiljanić Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17757 Fri, 29 Dec 2017 00:00:00 +0100 https://aseestant.ceon.rs/index.php/terteh/article/view/17795 <p class="TTAPSTRAKT">Na parnim kotlovima blokova B1 i B2 Termoelektrane „Nikola Tesla B“ je tokom prve faze kapitalnog remonta ugrađen dodatni ekonomajzer, sledstveno 2012. i 2016. godine. Dodatni ekonomajzer se napaja vodom pomoću posebne linije sa potisa napojne pumpe i paralelno je povezan sa delom osnovnog ekonomajzera. Napojna voda se većim delom šalje ka zagrejačima visokog pritiska (ZVP) u okviru osnovne napojne linije, dok se manji deo dovodi do dodatnog ekonomajzera. Dodatni ekonomajzer je povećao stepen korisnosti bloka za preko 0,5 procentnih poena, što omogućava proizvodnju sa oko 10 MW „zelene“ električne snage na račun iskorišćenja otpadne toplote dimnih gasova. Pored ovih značajnih energetskih, pratećih ekoloških i finansijskih efekata, ugradnja dodatnog ekonomajzera omogućava i primarnu i sekundarnu regulaciju snage. Povećanjem protoka napojne vode kroz dodatni ekonomajzer smanjuje se protok napojne vode kroz zagrejače visokog pritiska, sledstveno se smanjuje oduzimanje pare nakon ekspanzije u turbini visokog pritiska i oduzimanje na turbini srednjeg pritiska, a samim tim se povećava snaga turbine.U radu su prikazani postupak i rezultati numeričke simulacije promene snage parnih blokova B1 i B2 sa promenom protoka napojne vode kroz dodatni ekonomajzer. Protok napojne vode kroz dodatni ekonomajzer se sa početne vrednosti, koja iznosi 25% od protoka vode koja se dovodi isparivaču kotla, povećava na 40% za 15s. Dobijeni rezultati pokazuju da se usled smanjenja protoka napojne vode kroz ZVP smanjuje njihova toplona snaga za oko 20%. Smanjena kondenzacija dovodi do povećanja pritisaka na parnoj strani ZVP, što smanjuje oduzimanje pare iz turbine. Usled smanjenog oduzimanja, povećava se protok kroz turbinu srednjeg i turbinu niskog pritiska, tako da se ukupna snage turbine povećava za približno 10MW. Brzina promene temperature metala cevi ZVP je u dozvoljenim granicama. Dobijeni rezultati pokazuju da se promenom protoka napojne vode kroz dodatni ekonomajzer može ostvariti primarna i sekundarna regulacija snage blokova, pri čemu se ne menjaju pritisak, temperatura i protok sveže pare.</p> Vladimir Stevanović Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17795 Sun, 27 Aug 2017 00:00:00 +0200 https://aseestant.ceon.rs/index.php/terteh/article/view/17796 Boiler is very important part of power plant for development of industry and production, therefore its operation need to be optimized and at the same time its efficiency. Efficiency of boiler can be determined by two methods, direct and indirect method. Mentioned two methods are providing different information. Indirect method for determination of boiler efficiency includes all heat losses in the system, while direct method did not include any heat losses. In this paper are presented changes of the boiler efficiency related with coal characteristics, determined with indirect method (according to EN 12952, part 15). Influence of different characteristics of coal such as heating value, moisture and ash content on the boiler efficiency have been evaluated. According to the results of calculations and tests, combustion coal with higher heat value, increase boiler efficiency. In the paper also is analyzed influence of the other characteristics of coal to the boiler efficiency. Comparison of the calculation results with different coal characteristics, enables proper coal selection. In order to improve boilers efficiency different opportunities have been analyzed. Lidija Bureska Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17796 Sun, 27 Aug 2017 00:00:00 +0200 https://aseestant.ceon.rs/index.php/terteh/article/view/17756 Power plants face today, and will continue so in the future, a variety of challenges, along with many uncertainties as well. Overshadowed by an inevitable and burdensome transition to a low carbon economy as the most exploited subject, there are also numerous issues, often overseen or even neglected, that may make position of power plants critical with respect to the security of supply, particularly when considering a massive move of mobility towards electric drives or a high penetration of intermittent renewables, for example. Exposed to a brutal and often unfair competition with subsidized players on the open market, some power plants are being economically and/or politically disqualified by ones based on another kind of primary energy sources. Addressed briefly are the above and some other issues, including water-energy nexus, energy storage, clean coal and CCS technologies, decentralized generation, role of virtual power plants, smart networking, cyber threats, as well as energy price volatility, global recession, geopolitical concerns, cross-border cooperation, climate deal, strong or smart solutions for security of energy supply, and some other dilemmas, challenges and/or uncertainties attributed to power plants in the times to come. Miodrag M Mesarović Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17756 Sun, 27 Aug 2017 00:00:00 +0200 https://aseestant.ceon.rs/index.php/terteh/article/view/17791 As a renewable energy source that is environmentally friendly and cost-effective, the hydropower potential of Serbia represents a valuable common good and notable economic force in a development strategy of the country. It is an important component of the country’s overall energy balance, both at present and in the future. Seventy-seven percent of the hydropower potential of Serbia is technically and economically usable, based on the present energy situation in the country, the latest technical advances, and economic criteria. Out of this amount, eight percent could be generated in small-scale hydropower plants, with an installed capacity less than 10 MW. In order to promote acquisition of Green Certificates, stimulate the Clean Development Mechanism (CDM) projects and facilitate the Certified Emission Reduction (CER) trading, Serbia is shifting its development strategy towards renewable energy sources, particularly small-scale HPPs. The necessary project documentation has been prepared, nearly 1,000 potential locations for small-scale HPPs have been identified, and the legislative framework is being synchronized with a world-accepted practice in this field. This paper presents some technical possibilities for the construction of small-scale HPPs in Serbia. The attention is focused on the specific conditions, statistical parameters, and the legislative framework of the country. Svetlana Stevović Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17791 Sun, 27 Aug 2017 00:00:00 +0200 https://aseestant.ceon.rs/index.php/terteh/article/view/17794 <p class="TTAPSTRAKT">Pretvaranje električne energije u druge oblike energije i njeno skladištenje u periodima smanjene potrošnje ili raspoložive povećane proizvodnje, kao i proizvodnja električne energije u periodima povećane potražnje ili smanjene proizvodnje, jesu od krucijalnog značaja za stabilnost i efikasnost elektroenergetskog sistema. Ovaj zahtev je posebno izražen danas zbog ekspanzije uključivanja vetrogeneratora i solarnih elektrana u elektroenergetski sistem. Ovi obnovljivi izvori su inherentno promenljivi, kako u dnevnom periodu, tako i u periodima od nekoliko dana, nedelja ili meseci. Stoga je neophodno obezbediti zamenske kapacitete i postrojenja za akumulaciju energije. Različite tehnologija se mogu koristiti za konverziju i akumulaciju električne energije, ali jedina u potpunosti razvijena raspoloživa tehnologija velikog kapaciteta je bazirana na reverzibilnim hidroelektranama. U okviru ovog rada se razmatra potencijal reverzibilnih hidroelektrana za efikasno i ekonomski prihvatljivo skladištenje električne energije proizvedene u vetroelektranama, u solarnim elektranama, protočnim hidroelektranama i iz drugih obnovljivih izvora, kao iz konvencionalnih termoelektrana, uključujući i nuklearne elektrane. Gasnoturbinska postrojenja i gasni motori zagaĎuju okolinu i utiču na klimatske promene. Za realizaciju reverzibilnih hidroelektrana se koriste reke i jezera. MeĎutim, pored ovih rešenja sa korišćenjem prirodnih pogodnosti, pojavila su se nova rešenja, kao što je korišćenje mora kao donjeg rezervoara (Japan), ili predlozi da gornji rezervoar bude površinski, a donji podzemni, korišćenjem prirodnih kaviteta ispod tla. Analize pokazuju da je opravdano investirati u reverzibilne hidroelektrane. Primeri iz svetske prakse pokazuju da se rešenje sa podzemnom mašinskom halom može otplatiti za sedam do deset godina ili čak za pet godina pri ostvarivanju mogućeg maksimalnog prihoda. Reverzibilne hidroelektrane sa površinskim akumulacijama se mogu otplatiti čak za četiri do šest godina.</p> Gajić Aleksandar Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17794 Sun, 27 Aug 2017 00:00:00 +0200 https://aseestant.ceon.rs/index.php/terteh/article/view/17792 Mala hidroelektrana (mHE) koja se nalazi u okviru objekta HE „Bočac“ izgrađena je sa idejom o mogućoj višenamenskoj upotrebi. Jedan od načina upotrebe mHE, koji je predviđen projektom, je rad mHE u ulozi kućnog agregata HE „Bočac“. Pre tehničkog prijema objekta mHE, izvršena su neophodna podešavanja i ispitivanja opreme hidroagregata pred njegovo puštanje u rad. U radu je prikazan deo rezultata navedenih ispitivanja, koji se pre svega odnosi na režim rada mHE u ulozi kućnog agregata, odnosno kada agregat mHE napaja potrošače u ostrvskoj mreži. Navedeni režim rada agregat je sa stanovišta opreme najzahtevniji i kao takav je za analizu najinteresantniji. Prikazani su rezultati ispitivanja rada agregata prilikom trenutnog opterećenja i rasterećenja agregata, uključenjem i isključenjem različitih delova izolovane 35kV mreže, uključenjem i isključenjem potrošača u 0,4kV razvodu sopstvene potrošnje i potrošača u pomoćnim objektima HE „Bočac“. Dane Džepčeski Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17792 Sun, 27 Aug 2017 00:00:00 +0200 https://aseestant.ceon.rs/index.php/terteh/article/view/17797 <p class="TTAPSTRAKT">With the latest modernization and revitalization of blocks in Thermal Power Plant (TPP) Bitola (2010-2012), apart from increasing the power of each unit from 225 to 234,3 MWel, new regulating valves were installed in the section between Medium Pressure Turbine (MPH) and Low Pressure Turbine (LPT) enabling subtraction of steam for the purposes of district heating of Bitola. This also creates opportunity to connect power plant’s own central heating system, with installed heat capacity of approximately 26 MWh, to this heat source. This heating system is in operation for almost 35 years and the need for its revitalization and reconstruction, techno-economic analysis, investment costs, economic viability and return on investment period for the reconstruction are presented in this paper.</p> Vladimir Mijakovski Copyright (c) https://aseestant.ceon.rs/index.php/terteh/article/view/17797 Sun, 27 Aug 2017 00:00:00 +0200