Comparison of Convective Heat Transfer Effects in Impinging Slot and Circular Jets Confined by Plates With Different Inclination Angles

Abstract

In this study, the effects of heat transfer characteristics along the target impingement plate surfaces in impinging slot and circular turbulent air jets confined by plates with different inclination angles are experimentally investigated. Surface temperature measurements were conducted with a thermal imaging camera on the target impingement plate for inclination angles of confinement plate θ = 0°, 15°, 30° and 45°, rate of plate-to-plate spacing H/W(D) = 0.5, 1, 3, 6 and Reynolds numbers (Re) 20000 and 30000. The Nusselt distributions calculated from the measured temperature values are analyzed and the changes are evaluated according to the confining plate inclination angle, Reynolds number and rate of plate-to-plate spacing parameters. For both slot and circular jets, secondary top points become visible in the Nusselt number distributions on the impingement plate when the rate of plate-to-plate spacing is H/W(D)≤1 and the inclination angle of confinement plate is θ≤15°. As the interval among the plates increases, the influence of the secondary top points decreases and their positions shift towards the plate ends. As the angle of inclination of the confining plate increases, the secondary top points disappear rapidly for slot jets, but more slowly for circular jets.

Keywords

• Circular jet
• Inclined confined plate
• Nusselt distributions
• Secondary top points
• Slot jet

Farklı Eğim Açılı Levhalarla Sınırlandırılmış Çarpan Slot ve Dairesel Jetlerde Taşınımla Isı Transferi Etkilerinin Karşılaştırılması

Abstract

Bu çalışmada, farklı eğim açılı levhalarla sınırlandırılmış çarpan slot ve dairesel türbülanslı hava jetlerinde, hedef çarpma levhası yüzeyleri boyunca ısı transfer karakteristikleri etkileri deneysel olarak incelenmiştir. Sınırlayıcı levha eğim açısının θ = 0°, 15°, 30° ve 45°, levhalar arası açıklık oranı H/W(D) = 0.5, 1, 3, 6 ve Reynolds sayısının 20000 ile 30000 değerleri için hedef çarpma levhası boyunca termal kamera ile yüzey sıcaklık ölçümleri yapılmıştır. Ölçümlenen sıcaklık değerlerinden hesaplanan Nusselt dağılımları, sınırlayıcı levha eğim açısı, Reynolds sayısı (Re) ve levhalar arası açıklık oranı parametrelerine göre incelenip değişimler değerlendirilmiştir. Hem slot hem de dairesel jetlerde, levhalar arası açıklık oranının H/W(D)≤1 ve sınırlayıcı levha eğim açısının θ≤15° olduğu durumlarda, çarpma levhası üzerindeki Nusselt sayısı dağılımlarında ikincil pikler oluşmaktadır. Levhalar arası açıklık oranı arttıkça, ikincil piklerin etkisi azalmakta ve konumları levha uçlarına doğru kaymaktadır. Artan sınırlandırıcı levha eğim açısı ile birlikte, slot jetlerde ikincil pikler hızla kaybolurken, dairesel jetlerde bu durumun daha yavaş olduğu gözlenmiştir.

Keywords

• Dairesel jet
• eğimli sınırlandırıcı levha
• ikincil artışlar
• Nusselt dağılımları
• Slot jet

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