Doymuş Suyun Zorlanmış Taşınımda Kaynamasına İlişkin Prandtl Sayısı İyileştirmesi İçeren Yeni Bir Isı Transfer Korelasyonu

Bu çalışmada; suyun, doymuş zorlanmış taşınımda kaynamasına ilişkin ısı transfer katsayısını ITK öngören yeni bir korelasyon sunulmuştur. Korelasyon hem dikey hem de yatay konuma sahip tüpler ve eş-merkezli iç içe geçmiş tüpler için geçerlidir. Çalışmanın temel amacı, Colburn andırımını derivasyona ekleyerek, doymuş zorlanmış taşınımda kaynama için Prandtl sayısının ITK üzerindeki olası etkisini araştırmaktır. Derivasyon, akış rejimine duyarlı olabileceği düşünülen ve bu noktadan sonra A olarak adlandırılan yeni bir boyutsuz sayı ile son bulmuştur. RELAP5/Mod3.3 ısıl-hidrolik sistem analiz kodunun akış haritalama prosedürüyle yapılan karşılaştırma sayesinde, A’nın iki fazlı akış rejimlerine bağlı olduğu konusunda ihtiyatlı bir çıkarım yapılmıştır. Önerilen korelasyonun titizlikle değerlendirilmesi, yeni korelasyonun kabul edilebilir bir doğruluğa sahip olduğunu ve deneysel ITK verilerini, doymuş zorlanmış taşınımda kaynama için 16.6%’lık ortalama sapma ile tahmin ettiğini açıkça ortaya koymaktadır. Ek olarak, Prandtl sayısı etkisinin göz önünde bulundurulmadığı en yakın korelasyona göre ortalama sapmadaki 1.5%’lik iyileşme, Prandtl sayısı iyileştirmesinin ITK üzerindeki olumlu etkisine bağlanmıştır

Anahtar Kelimeler:

Korelasyon, Zorlanmış taşınımda kaynama, Akış haritalaması, Prandtl sayısı iyileştirmesi

A new heat transfer correlation for saturated flow boiling of water with Prandtl number improvement

A new correlation predicting the heat transfer coefficient HTC for the saturated flow boiling of water is presented in this study. The correlation is valid for tubes and annuli having both vertical and horizontal orientations. The fundamental aim of the study is to investigate the likely effect of the Prandtl number on the HTC for saturated flow boiling by adding the Colburn analogy into the derivation. The derivation was ended up with a new dimensionless number, hereafter called as A, and it has been suspected that A may be sensitive to the flow regime. Thanks to the comparison carried out with the flow mapping procedure of the RELAP5/Mod3.3 system analysis code, it was made prudent inference that A is dependent on the two-phase flow regimes. Rigorously evaluation of the proposed correlation makes clear that new correlation possesses admissible accuracy and that predicts the experimental HTC data with 16.6% mean deviation for saturated flow boiling. In addition,1.5% improvement in the mean deviation as per the closest correlation in which the Prandtl number effect is not considered is attributed to the positive effect of the Prandtl number improvement on HTC.

Keywords:

Flow boiling, Correlation, Prandtl number improvement, Flow mapping.,

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