Experimental Investigation of The Transition Process With Single-Phase And Two-Phase Flow Regions In Horizontal Pipes In Terms Of Heat Transfer

Öz

In this study, the effects of flow transition from single-phase (liquid) to two-phase (liquid-vapor) regime on heat transfer in a two-phase flow system in a horizontal pipe are experimentally investigated. The behavior of the flow under different mass flow rates, inlet temperatures and heat input levels were analyzed in the experimental system. In the single-phase flow regime, heat transfer is mainly limited by forced convection mechanisms, whereas in the two-phase region, as the fluid reaches saturation temperature and starts to evaporate, significant increases in the heat transfer coefficient are observed due to complex phenomena associated with phase change such as vapor bubble formation, interfacial movements and condensation. The change in the Nusselt number, the vaporization onset points and the characteristics of the transition regimes in this transition region were evaluated in detail. In addition, the location and width of the transition region are determined by experimental data, emphasizing the critical role of this region in terms of heat transfer performance. The results obtained provide engineering data that will contribute to more efficient design of thermal systems such as evaporators and heat exchangers.

Anahtar Kelimeler

• two-phase flow
• single-phase flow
• heat transfer
• pressure drop

Yatay Borularda Tek Fazli Ve İki Fazli Akiş Bölgeleri İle Geçiş Sürecinin Isı Transferi Açisindan Deneysel İncelenmesi

Öz

Bu çalışmada, yatay bir boru içerisinde gerçekleşen iki fazlı akış sisteminde, akışın tek fazlı (sıvı) rejimden iki fazlı (sıvı-buhar) rejime geçişinin ısı transferi üzerindeki etkileri deneysel olarak incelenmiştir. Deneysel sistemde farklı kütlesel debiler, giriş sıcaklıkları ve ısı girdisi seviyeleri altında akışın davranışı analiz edilmiştir. Tek fazlı akış rejiminde ısı transferi esas olarak zorlanmış taşınım mekanizmalarıyla sınırlıyken; akışkanın doygunluk sıcaklığına ulaşarak buharlaşmaya başlamasıyla birlikte, iki fazlı bölgede buhar kabarcığı oluşumu, ara yüzey hareketleri ve yoğuşma gibi faz değişimiyle ilişkili karmaşık fenomenlerin etkisiyle ısı transfer katsayısında belirgin artışlar gözlemlenmiştir. Bu geçiş bölgesinde Nusselt sayısındaki değişim, buharlaşma başlangıç noktası ve geçiş rejimlerinin özellikleri ayrıntılı olarak değerlendirilmiştir. Ayrıca, geçiş bölgesinin yeri ve genişliği deneysel verilerle belirlenmiş, bu bölgenin ısı transfer performansı açısından taşıdığı kritik rol vurgulanmıştır. Elde edilen sonuçlar, buharlaştırıcılar ve ısı değiştiriciler gibi termal sistemlerin daha verimli tasarlanmasına katkı sağlayacak nitelikte mühendislik verileri sunmaktadır.

Anahtar Kelimeler

• iki fazlı akış
• tek fazlı akış
• ısı transferi
• basınç düşümü

Kaynakça

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