Nozul Mesafesinin Çarpan Jet Isı Transferi ve Akışkan Akışı Üzerindeki Etkileri

Abstract

Bu çalışmada dikey düz bir plaka yüzeyine çarpan jet akışı için nozul uzunluğunun ısı transferi ve akış alanı üzerindeki etkileri sayısal olarak araştırılmıştır. Çalışmanın temel amacı, sabit ısı akısına (q=1500 W/m2) sahip bir yüzeydeki ısı transferini etkileyen nozul uzunluğuna bağlı jet çarpmasının akış özellikleri üzerindeki etkilerini göstermektir. Analizler bir Hesaplamalı Akışkanlar Dinamiği (HAD) uygulaması olan Ansys/Fluent kullanılarak elde edilmiştir. Nozul çıkışındaki akış, tam gelişmiş bir hız profiline sahiptir. Analizler, nozul ile plaka yüzeyi arasında 0,5; 1 ve 1,5 L/W boyutsuz mesafeleri ile 1300, 2600 ve 4000 jet Reynolds sayısı (Re) için gerçekleştirilmiştir. Sonuçlar, durma noktası bölgesinde azalan nozul mesafesi ile yerel Nusselt sayılarının arttığını göstermektedir. Bu durum, ısı transferinin artmasıyla sonuçlanan daha düşük nozul mesafesi çapı ile jet momentumu ve türbülans yoğunluğu seviyesindeki bir artışa ve ısıl sınır tabaka incelmesine bağlanabilir. Ayrıca zamana bağlı yapılan çözümlemede, hız ve sıcaklık konturları verilmiş, Nusselt sayısı ile sıcaklık değişim grafikleri sunularak modeller birbirleriyle karşılaştırılmıştır.

Keywords

• Jet akışı
• Jet çarpması
• Nozul
• Isı transferi

The Effects of Nozzle Distance on Impinging Jet Heat Transfer and Fluid Flow

Abstract

In this study, the effects of nozzle length on heat transfer and flow area for jet flow impinging on a vertical flat plate surface were investigated numerically. The main purpose of the study is to show the effects of jet impingement on the flow properties, depending on the nozzle length, which affects the heat transfer on a surface with a constant heat flux (q"=1500 W/m2). Analyzes were obtained using Ansys/Fluent, a Computational Fluid Dynamics (CFD) application. The flow at the nozzle outlet has a fully developed velocity profile. Analyzes were performed for 1300, 2600 and 4000 jet Reynolds numbers (Re) with dimensionless distances of 0.5, 1 and 1.5 L/W between the nozzle and the plate surface. The results show that local Nusselt numbers increase with decreasing nozzle distance in the stagnation point region. This can be attributed to an increase in jet momentum, turbulence intensity and thermal boundary layer thinning with the smaller nozzle distance diameter resulting in increased heat transfer. In addition, time-dependent velocity and temperature contours are given, Nusselt number and temperature change graphs are presented along the vertical plate and the models are compared with each other. 

Keywords

• Jet flow
• Jet impigment
• Nozzle
• Heat transfer

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