Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes
Yıl: 2012 Cilt: 32 Sayı: 1 Sayfa Aralığı: 19 - 31 Metin Dili: Türkçe İndeks Tarihi: 29-07-2022
Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes
Öz: Bu çalışmada, iç çapı 7 mm ve uzunluğu 500 mm olan iç yüzeyi pürüzsüz ve mikro kanatlı borular içinde akanR134a’nın laminar film yoğuşması ısı transferi katsayısının deneysel karşılaştırılması sunulmuştur. Yoğuşma deneyleri29 kg $m^{-2}s^{-1}$kütlesel akılarında yapılmıştır. Basınçlar 0.8-0.9 MPa değerleri arasındadır. Halka akışı şartlarında geçerliolan iç yüzeyi pürüzsüz boruya ait olan ısı transferi modeli, literatürde yaygın olarak kullanılan bir sürtünme katsayısıile boru iç yüzeyindeki mikro kanatların varlığından ötürü meydana gelen ısı transferi iyileşmesini hesaba katacakşekilde modifiye edilmiştir. Düşey olarak yoğuşan film esansındaki yerel ısı transferi katsayılarındaki değişim ve boruboyunca oluşan yoğuşma miktarı, doyma sıcaklığı ile boru iç yüzeyindeki sıcaklık farkı ve yoğuşma sıcaklığı dadikkate alınarak bulunmuştur.Sonuçlar arayüzey kayma gerilmesinin çalışmada belirtilen şartlarda R134a’nın lamineryoğuşma ısı transferi üzerinde öneme sahip olduğunu ve önerilen modelin arayüzey kayma gerilmesinin etkisininihmal edildiği geleneksel çözümden daha iyi sonuçlar vermesiyle göstermiştir. Ayrıca, yoğuşma basınçlarına göre ısıtransferi katsayıları da karşılaştırılmıştır. Pratik uygulamalar için test edilen borulara ait yeni amprik yoğuşma ısıtransferi eşitlikleri önerilmiştir.
Anahtar Kelime: Konular:
İç yüzeyi pürüzsüz ve mikro kanatlı düşey borularda r134a’nın laminer akışındaki yoğuşması sırasında meydana gelen ısı transferi iyileşmesinin araştırılması
Öz: This paper presents an experimental comparison of the laminar film condensation heat transfer coefficientsof R134a in vertical smooth and micro-fin tubes having inner diameters of 7 mm and lengths of 500 mm.Condensation experiments were performed at a mass flux of 29 kg $m^{-2}s^{-1}$ . The pressures were between 0.8 and 0.9MPa. The original smooth tube heat transfer model was modified by a well-known friction factor to account for theheat transfer enhancement effects due to the presence of micro-fins on the internal wall surface during annular flowregime conditions. Alterations of the local heat transfer coefficient, and condensation rate along the tube length duringdownward condensing film were determined, considering the effects of the temperature difference between thesaturation temperature and the inner wall temperature of the test tubes, and the condensing temperature on these items.The results show that the interfacial shear stress is found to have significance for the laminar condensation heattransfer of R134a under the given conditions due to its better predictive performance than the classical solutionneglecting the interfacial shear stress effect. A comparison of the condensation heat transfer coefficients was also doneaccording to the condensing pressures. New empirical correlations of the condensation heat transfer coefficientbelonging to the test tubes are proposed for practical applications.
Anahtar Kelime: Konular:
Belge Türü: Makale Makale Türü: Araştırma Makalesi Erişim Türü: Erişime Açık
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| APA | DALKILIÇ A, TEKE İ, Wongwises S (2012). Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. , 19 - 31. |
| Chicago | DALKILIÇ Ahmet Selim,TEKE İsmail,Wongwises Somchai Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. (2012): 19 - 31. |
| MLA | DALKILIÇ Ahmet Selim,TEKE İsmail,Wongwises Somchai Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. , 2012, ss.19 - 31. |
| AMA | DALKILIÇ A,TEKE İ,Wongwises S Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. . 2012; 19 - 31. |
| Vancouver | DALKILIÇ A,TEKE İ,Wongwises S Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. . 2012; 19 - 31. |
| IEEE | DALKILIÇ A,TEKE İ,Wongwises S "Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes." , ss.19 - 31, 2012. |
| ISNAD | DALKILIÇ, Ahmet Selim vd. "Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes". (2012), 19-31. |
| APA | DALKILIÇ A, TEKE İ, Wongwises S (2012). Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. Isı Bilimi ve Tekniği Dergisi, 32(1), 19 - 31. |
| Chicago | DALKILIÇ Ahmet Selim,TEKE İsmail,Wongwises Somchai Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. Isı Bilimi ve Tekniği Dergisi 32, no.1 (2012): 19 - 31. |
| MLA | DALKILIÇ Ahmet Selim,TEKE İsmail,Wongwises Somchai Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. Isı Bilimi ve Tekniği Dergisi, vol.32, no.1, 2012, ss.19 - 31. |
| AMA | DALKILIÇ A,TEKE İ,Wongwises S Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. Isı Bilimi ve Tekniği Dergisi. 2012; 32(1): 19 - 31. |
| Vancouver | DALKILIÇ A,TEKE İ,Wongwises S Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes. Isı Bilimi ve Tekniği Dergisi. 2012; 32(1): 19 - 31. |
| IEEE | DALKILIÇ A,TEKE İ,Wongwises S "Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes." Isı Bilimi ve Tekniği Dergisi, 32, ss.19 - 31, 2012. |
| ISNAD | DALKILIÇ, Ahmet Selim vd. "Heat transfer enhancement during downward laminar flow condensation of r134a in vertical smooth and microfin tubes". Isı Bilimi ve Tekniği Dergisi 32/1 (2012), 19-31. |
