Marangonijeva konvekcija pri pothlađenom mehurastom ključanju

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Sanja Petrović

Apstrakt

Kretanje tečnosti prouzrokovano varijacijom sila površinskog napona, nazvano Marangonijev efekat, i njen doprinos razmeni toplote ključanjem, u prošlosti je predstavljalo izuzetno kontroverznu temu. Klasična teorija razmene toplote ključanjem, iako priznajući postojanje navedenog efekta, smatra njegov doprinos razmeni toplote zanemarljivim, zbog velike razlike u gustinama tečnosti i pare i prisustva gravitacionog polja, a samim tim i dominacije prirodne konvekcije. Međutim, noviji eksperimenti obavljeni u mikrogravitacijskoj sredini pokazali su da su, iako je sam mehanizam ključanja u takvoj sredini drugačiji nego na zemlji, odgovarajuće količine razmenjene toplote slične onima izmerenim u uslovima normalne gravitacije. Kako u izvršenim eksperimentima prirodna konvekcija nije bila dominantan faktor zbog zanemarljivog gravitacionog polja, ostvareni rezultati pokrenuli su mnogobrojna pitanja o ispravnosti pretpostavke da Marangonijev efekat ne doprinosi u vecoj meri količini toplote razmenjene ključanjem. Na osnovu ranije navedenih saznanja, u ovom članku biće izloženi rezultati i zaključci eksperimentalne studije u kojoj je destilovana voda postepeno zagrevana do ključanja na bakarnoj grejnoj površini i to u uslovima četiri različita nivoa pothlađenja. Kao podrška merenjima, dešavanja na grejnoj površini fotografski su zabeležena digitalnom kamerom. Dobijeni rezultati ukazuju da Marangonijeva konvekcija, povezana sa izdvajanjem mehurića vazduha iz vode, kada je ona dovoljno zagrejana, u značajnoj meri utiče na količinu razmenjene toplote u uslovima pothlađenog mehurastog bazenskog ključanja. U cilju objašnjenja uočenog fenomena razvijen je teorijski model koji podržava uslove eksperimentalnog istraživanja.

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Kako citirati
PETROVIĆ, Sanja. Marangonijeva konvekcija pri pothlađenom mehurastom ključanju. KGH – Klimatizacija, grejanje, hlađenje, [S.l.], v. 33, n. 4, p. 13-23, dec. 2016. ISSN 2560-340X. Dostupno na: <https://izdanja.smeits.rs/index.php/kgh/article/view/938>. Datum pristupa: 07 may 2021
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