Experımental Investigation of Heat Transfer Characteristics in Unconfined and Confıned Impinging Jet Arrays with 45° Inclined Secondary Jets

Öz

In this study, the heat transfer effects at the impingement surface in unconfined and confined impinging array jet flows with 45° inclined secondary jets are experimentally investigated. In the unconfined and confined jet flow fields, temperature distributions were obtained with a thermal camera along the center axis of the impingement plate for 20000 and 30000 values of the Reynolds number and 0,5, 1, 3 and 6 values of the nozzle-to-plate/inter-plate spacing. From the obtained temperature distributions, the effect of Reynolds number, nozzle-to-plate/inter-plate spacing and the presence of a confinement plate on the Nusselt distributions on the impingement plate were investigated. In both unconfined and confined cases, the Nusselt values on the impingement plate increase with increasing Reynolds number and decrease with increasing nozzle-to-plate/inter-plate spacing. At the stagnation point on the impingement plate in the direction of the axis of the primary nozzle and at the position of the impingement plate in the direction of the axes of the secondary jets, the local Nusselt number takes peak values. The peaks on the impingement plate become sharper as the Reynolds number increases. The positions of the peaks formed by the secondary jets on the impingement plate shift to larger ±r/D values with increasing nozzle-to-plate/inter-plate spacing. The presence of a confinement plate in the flow fields reduces the Nusselt values on the impingement plate.

Anahtar Kelimeler

• Impinging jet array
• Inclined secondary jet
• Unconfined jet
• Confined jet
• Nusselt number distribution

45° Eğimli İkincil Jetlere Sahip Sınırlandırılmamış ve Sınırlandırılmış Çarpan Jet Dizilerinde Isı Transferi Karakteristiklerinin Deneysel İncelenmesi

Öz

Bu çalışmada, 45° eğimli ikincil jetlere sahip sınırlandırılmamış ve sınırlandırılmış çarpan dizi jet akışlarında çarpma yüzeyindeki ısı transferi etkileri deneysel olarak incelenmiştir. Sınırlandırılmamış ve sınırlandırılmış jet akış alanlarında, Reynolds sayısının 20000 ve 30000 değerleri ve lüle-levha/levhalar arası açıklığın 0,5, 1, 3 ve 6 değerleri için çarpma levhasının orta ekseni boyunca termal kamera ile sıcaklık dağılımları elde edilmiştir. Elde edilen sıcaklık dağılımlarından, Reynolds sayısının, lüle-levha/levhalar arası açıklığın ve sınırlayıcı levha varlığının çarpma levhası üzerindeki Nusselt dağılımlarına etkisi araştırılmıştır. Hem sınırlandırılmamış hem de sınırlandırılmış durumda, çarpma levhası üzerindeki Nusselt değerleri artan Reynolds sayısı ile artmakta, artan lüle-levha/levhalar arası açıklıkla azalmaktadır. Çarpma levhası üzerinde birincil lüle ekseni doğrultusundaki durma noktasında ve ikincil jetlerin eksenleri doğrultusundaki çarpma levhası konumlarında yerel Nusselt sayısı pik değerler almaktadır. Çarpma levhası üzerinde oluşan pikler, Reynolds sayısı arttıkça daha keskin hale gelmektedir. İkincil jetlerin çarpma levhası üzerinde oluşturdukları piklerin konumları artan lüle-levha/levhalar arası açıklı ile daha büyük ±r/D değerlerine kaymaktadır. Akış alanlarında sınırlayıcı levhanın varlığı, çarpma levhası üzerindeki Nusselt değerlerini azaltmaktadır.

Anahtar Kelimeler

• Çarpan dizi jet
• Eğimli ikincil jet
• Sınırlandırılmamış jet
• Sınırlandırılmış jet
• Nusselt sayısı dağılımı

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