17 KB607 KB15 KB200020242012Hnizdil, MilanHwang, Jong YeonKim, Seong YeonLee, Sang HyeonRaudensky, Miroslavštevilka:3letnik:46str. 311-315ISSN:1580-2949COBISSID:935594URN:URN:NBN:SI:doc-9WU05GTKenInštitut za kovinske materiale in tehnologijeMateriali in tehnologijecontinuous castingcoolingcooling intensityintenziteta hlajenjakontinuirno ulivanjemeglične šobemist nozzlesohlajanjetemperatura vodewater temperatureInfluence of the water temperature on the cooling intensity of mist nozzles in continuous casting| Vpliv temperature vode na intenziteto ohlajanja z megličnimi šobami pri kontinuirnem ulivanju|Small mist nozzles used in continuous casting were tested for heat-transfer intensity. These nozzles are used in the secondary cooling area of a steel slab casting machine. The impact pressure distribution was measured first. The laboratory measurements of the cooling intensity (the HTC distribution) were performed with a variable water temperature. A temperature range from 20 °C to 80 °C was used in the tests. Surprisingly, the water temperature was found to have a strong influence. The most noticeable effect is a shift in the Leidenfrost temperature to low temperatures. Changing the water temperature from 20 °C to 80 °C caused a change in the Leidenfrost temperature of 130 °C. This can be significant and can change the cooling character of the continuous casting machine. It is interesting that with an increase in the cooling intensity, following an increase in the water temperature in a high-temperature region (above the Leidenfrost temperature), there is a small difference of about 30 W/(m2 K). Surprisingly, high differences in the Leidenfrost temperature were found for an intensive cooling, where a difference of only 20 °C in the coolant temperature makes a difference of about 100 °C in the Leidenfrost temperature. The results of the experiments performed with an elevated water temperature showed a high sensitivity of the cooling intensity to this parameter. The decreasing effect of the cooling intensity related to the water temperature is more important for the spray cooling of high intensitiesMajhne meglične šobe, ki se uporabljajo pri kontiuirnem ulivanju jekla, so bile preizkušene na intenziteto prenosa toplote. Te šobe se uporabljajo v območju sekundarnega hlajenja kontinuirne naprave za ulivanje jekla. Najprej je bila izmerjena razporeditev tlaka pri njegovem udarcu. Laboratorijske meritve intenzitete ohlajanja (razporeditev koeficienta prenosa toplote) so bile izvršene s spreminjanjem temperature vode. Pri preizkusih je bila uporabljena voda s temperaturo od 20 °C do 80 °C. Presenetljivo je, da se je izkazalo, da ima temperatura vode močan vpliv. Najbolj opazen učinek je bil premik Leidenfrostove temperature k nižjim vrednostim. Sprememba temperature vode iz 20 °C na 80 °C je povzročila spremembo Leidenfrostove temperature za 130 °C. To je pomembno in lahko močno vpliva na ohlajevalne značilnosti naprave za kontinuirno ulivanje. Zanimivo je, da se z naraščanjem intenzitete ohlajanja z višanjem temperature vode v visokotemperaturnem režimu (nad Leidenfrostovo temperaturo) opazi le majhna sprememba HTC za okrog 30 W/(m2 K). Presenetljivo velike razlike v Leidenfrostovi temperaturi so bile dobljene pri intenzivnem ohlajanju, kjer je razlika v temperaturi vode 20 °C povzročila razliko v Leidenfrostovi temperaturi za okrog 100 °C. Rezultati eksperimentov, izvršeni s povišano temperaturo vode, so pokazali veliko občutljivost intenzitete ohlajanja za temperaturo vode. Padajoči učinek intenzitete ohlajanja z naraščanjem temperature vode je bolj pomemben pri bolj intenzivnem ohlajanju z megloTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije