Experimental Investigation of Thermal Behavior of Swirling Coaxial Impinging Air Jet for Near-Field Impingement Cases

Year 2020, Volume: 12 Issue: 2, 443 - 453, 30.06.2020

Burak Markal

https://doi.org/10.29137/umagd.705238

Abstract

In this study, at the near-field impingement cases, the heat transfer characteristics of swirling coaxial impinging jets are experimentally investigated. In this context, different values of the dimensionless nozzle-to-plate distance (H / D = 0.2, 0.5, 0.75, 1.0) and the flowrate ratio (Q* = 0.33, 0.5, 0.66) are studied; and the combined effect of dimensionless nozzle-to-plate distance and flowrate ratio on thermal performance is researched. In the experiments, the total flowrate is kept constant at the value of 30 L/min; while the heating power is adjusted at the value of 18.2 W. A comparison with the conventional round jets is also performed over the temperature distribution of impingement plate. As a general trend, with increasing flowrate ratio, the area-averaged Nusselt numbers increase and the distribution of local Nusselt numbers has a more uniform character in the radial direction. For the smallest flowrate ratio and nozzle-to-plate distance, a significant enhancement occurs in the uniformity of heat transfer at the impingement region. Swirling coaxial jets improve the thermal performance much more compared to the conventional type jets.

Keywords

Near-field impingement, thermal performance, swirling co-axial jets

Dönmeli Eş-Eksenli Hava Jetinin Isıl Davranışının Yakın Çarpma Mesafeleri için Deneysel Olarak İncelenmesi

Abstract

Bu çalışmada, yakın çarpma mesafesi değerlerinde, dönmeli eş-eksenli çarpan jetlerin ısı transfer karakteristikleri deneysel olarak incelenmiştir. Bu kapsamda, farklı boyutsuz lüle-plaka arası mesafeler (H / D = 0.2, 0.5, 0.75, 1.0) ve debi oranlarında (Q* = 0.33, 0.5, 0.66) çalışılmış ve boyutsuz lüle-plaka arası mesafe ile debi oranının ısıl performans üzerindeki bütünleşik etkisi araştırılmıştır. Deneylerde, toplam debi 30 L/dk değerinde sabit tutulmuş olup; ısıtma gücü, tüm koşullarda 18.2 W değerine ayarlanmıştır. Ayrıca, çarpma plakasının sıcaklık dağılımları üzerinden konvansiyonel dairesel jetlerle karşılaştırma da yapılmıştır. Genel eğilim olarak, artan debi oranı ile alan ağırlıklı ortalama Nusselt sayıları artmakta ve yerel Nusselt sayısı dağılımları radyal doğrultuda daha üniform karaktere sahip olmaktadır. En küçük debi oranı ve lüle-plaka arası mesafe için çarpma bölgesinde ısı transferinin üniformluğunda belirgin bir iyileşme meydana gelmektedir. Dönmeli eş-eksenli jetler, konvansiyonel tip jetlere kıyasla ısıl performansı önemli ölçüde artırmaktadır.

Keywords

Yakın çarpma mesafesi, ısıl performans, dönmeli eş-eksenli jet

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