Konik sarımlı yay elemanlarının kaynamalı iki fazlı akış rejimlerine etkisi

Öz

Bu çalışmada, yatay borularda gerçekleşen iki fazlı kararlı akış koşullarında, yüzey artırıcı eleman olarak kullanılan konik sarımlı yay (çapı azalan ve artan yönde) dizisinin ısı transferi ve akış kararsızlıklarına etkisi deneysel olarak incelenmiştir. Deneyler, sabit giriş sıcaklığı (15 °C), sabit ısıl güç (22 kW) ve sabit çıkış kısıtlaması altında iki farklı boru tipinde (boş boru ve konik yay dizili boru) gerçekleştirilmiştir. Kütlesel debi 72 g/s’den başlayarak 17 g/s’ye kadar kademeli olarak azaltılmış ve her kademede sistemin kararlı duruma ulaşması beklenerek ölçümler alınmıştır. Deneysel sonuçlar, yüzey artırıcı eleman kullanılan boruda (Boru-2) basınç düşümünün düz boruya (Boru-1) kıyasla daha yüksek olduğunu, ancak akışın daha homojen ve dengeli bir şekilde gerçekleştiğini göstermektedir. Ayrıca, cidar sıcaklıkları daha düşük seviyelerde seyretmiş ve üst-alt cidar sıcaklıkları arasındaki fark azalmıştır. Bu durum, konik yay elemanının oluşturduğu türbülans sayesinde sıvı ve buhar fazlarının daha iyi karışmasına bağlanmıştır. Burn-out olayının daha düşük sıcaklıklarda gerçekleştiği, böylece boru cidarının aşırı ısınmaya karşı daha iyi korunduğu gözlemlenmiştir. Elde edilen veriler, bu tür yüzey artırıcı elemanların iki fazlı ısı transfer sistemlerinde ısıl performansı artırırken aynı zamanda sistem kararlılığını da olumlu yönde etkilediğini ortaya koymuştur. Çalışma, özellikle kaynamalı akış içeren mühendislik sistemlerinde, güvenli ve verimli tasarım açısından önemli katkılar sunmaktadır.

Anahtar Kelimeler

• İki fazlı akış
• Kaynamalı ısı transferi
• Akış kararsızlığı
• Isı transferi iyileştirmesi
• Konik yay

Effect of conical helical spring elements on boiling two-phase flow regimes

Öz

In this study, the effects of a conical helical spring insert (with decreasing and increasing diameter along the flow direction), used as a surface enhancement element, on heat transfer and flow instability under steady-state two-phase flow conditions in horizontal tubes were experimentally investigated. The experiments were conducted at a constant inlet temperature (15 °C), a constant heat input (22 kW), and a fixed outlet restriction, using two different tube configurations: a smooth tube and a tube equipped with a conical helical spring insert. The mass flow rate was gradually decreased from 72 g/s to 17 g/s, and measurements were taken after the system reached steady-state conditions at each stage. Experimental results showed that the pressure drop in the tube with the surface enhancement element (Tube-2) was higher compared to the smooth tube (Tube-1), but the flow occurred more homogeneously and uniformly. Moreover, the wall temperatures were observed to be lower, and the temperature difference between the upper and lower tube walls decreased. This behavior is attributed to improved mixing of the liquid and vapor phases due to turbulence generated by the conical helical spring. The burn-out phenomenon occurred at lower wall temperatures, indicating better protection of the tube wall against overheating. The results indicate that these surface enhancement elements not only improve thermal performance in two-phase heat transfer systems but also enhance flow stability. This study provides important insights for achieving safe and efficient designs, especially in engineering systems involving boiling flow.

Anahtar Kelimeler

• Two-phase flow
• Boiling heat transfer
• Flow instability
• Heat transfer enhancement
• Conical spring

Kaynakça

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