Kaldırma Kuvveti ve Yüzey Işınımının Eğik Bir Plakanın Çarpan Jet ile Soğutulmasına Etkilerinin Sayısal Olarak İncelenmesi

Abstract

Bu çalışmada, eğik bir plakanın tek bir slot jet ile soğutulmasında kaldırma kuvveti ve yüzeyler arası ışınımın taşınımla ısı transferine etkileri sayısal olarak incelenmiştir. Çalışma jet Reynolds sayısının (Re_j) 100 ile 1000 değerleri arasında gerçekleştirilmiş olup Richardson sayısı (Ri) ise 0.1 ile 10 arasında değişmektedir. Yüzeyler arası ışınımla ısı transferinin genel ısı transfer performansına etkileri hedef plaka ve sınırlandırıcı yüzeylerin üç farklı yayıcılık (ε=0.05-0.5-0.95) değeri ve üç farklı eğim açısı (α=0°-5°-10°) için analiz edilmiştir. Boyutsuz hedef plaka-nozul çapı mesafesi (H/D_j) 4’e eşit olup havanın (Pr=0.71) ışınım açısından katılımcı olmadığı kabulüyle hesaplamalar gerçekleştirilmiştir. Çalışma sonucunda, yüksek Richardson sayılarında kaldırma kuvvetinin akış ve ısı transfer karakteristiklerinin üzerindeki etkisinin ihmal edilemeyecek düzeyde olduğu, yüzey yayıcılığının artışının ise genel ısı transfer performansını iyileştirdiği ve plaka eğiminin ısı transferini önemli ölçüde etkilediği belirlenmiştir.

Keywords

• Çarpan jet
• Taşınım
• Işınım
• Yüzey yayıcılığı
• Kaldırma kuvveti
• Eğim

Numerical Investigation of the Effects of Buoyancy and Inter-Surface Radiation on Jet Impingement Cooling of an Inclined Plate

Abstract

In this study, effects of buoyancy and inter-surface radiation on convective heat transfer from an inclined plate cooled by a slot jet are numerically investigated. The study is carried out between the values of jet Reynolds number (Re_j) 100 and 1000, and the Richardson number (Ri) varies between 0.1 and 10. Impact of inter-surface radiation on the overall heat transfer performance is analyzed for three emissivity (ε=0.05-0.5-0.95) values of the target plate and confined surfaces and three different inclination angles (α=0°-5°-10°) of the target plate. The dimensionless nozzle-to-target plate spacing (H/D_j) equals to 4, and computations are performed assuming that air (Pr =0.71) is not participating for radiation. As a result of the study, it is determined that effect of buoyancy on the flow and heat transfer characteristics at high Richardson numbers cannot be neglected, while the increase in surface emissivity improves the overall heat transfer performance and inclination of the target plate significantly affects the heat transfer.

Keywords

• jet impingement
• convection
• radiation
• surface emissivity
• buoyancy
• inclination

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