ANALYSIS OF THE TWO PHASE FLOW PRESSURE DROP TYPE OSCILLATIONS IN A WATER BOILING HORIZONTAL STRAIGHT TUBE

Öz

   Two phase flows occur in many industrial applications such as refrigeration systems, turbo machinery, and power plant heat exchangers. Prediction of flow parameters is very crucial in design of two-phase flow equipment. Oscillations incurred by instabilities in two-phase flow systems cause mechanical vibrations, boiling crisis, high transient temperatures, control problems and even burnout at wall surface. This study is focused on determining steady state characteristic curves for certain inlet temperature and exit restriction conditions at different mass flow rates and compares variation of pressure drop type dynamic two phase flow instabilities in horizontal tube system. This work aims to predict low frequency pressure drop type oscillations in an in-tube boiling system. Results provide further understanding of mechanism of pressure-drop-type instabilities in a horizontal boiling tube system. They can also be utilized as guidance for design and control strategy of systems to avoid serious oscillation problems. 

Anahtar Kelimeler

• Two phase flow instabilities,pressure drop type instabilities,density wave type instabilities,stability boundary,inlet sub-cooling

SU KAYNAMALI YATAY DÜZ BORUDA İKİ FAZLI AKIŞ BASINÇ DÜŞÜMÜ OSİLASYONLARININ ANALİZİ

Öz

   İki fazlı akışlar, soğutma sistemleri, turbo makineler ve enerji santrallerindeki ısı eşanjörleri gibi birçok endüstriyel uygulamada ortaya çıkar. İki fazlı akış ekipmanlarının tasarımında akış parametrelerinin tahmini çok önemlidir. İki fazlı akış sistemlerinde kararsızlıklardan kaynaklanan salınımlar mekanik titreşimlere, kaynama krizine, yüksek geçiş sıcaklıklarına, kontrol problemlerine ve hatta cidarda ani sıcaklık yükselmesine neden olur. Bu çalışma, belirli giriş sıcaklığı ve çıkış kısıtlaması şartlarında değişik debilerde kararlı hal karakteristik eğrilerini belirleme üzerine odaklanmıştır ve yatay borulu sistemdeki basınç düşümü tipi iki fazlı akış dinamik kararsızlıklarının değişimlerini karşılaştırmaktadır. Bu çalışma, borulu kaynama sisteminde düşük frekanslı salınımları öngörmeyi amaçlamaktadır. Sonuçlar, yatay kaynamalı boru sisteminde basınç düşümü tipi kararsızlık mekanizmasının daha iyi anlaşılmasını sağlar. Ayrıca, ciddi salınım problemlerinden kaçınmak için sistemlerin tasarım ve kontrol stratejileri için kılavuz olarak da kullanılabilirler.

Anahtar Kelimeler

• İki fazlı akım istikrarsızlıkları,basınç düşüşü tipi istikrarsızlıklar,yoğunluk dalga tipi istikrarsızlıklar,stabilite sınırı,giriş aşırı soğutma

Kaynakça

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