DÜZ BİR LEVHA ÜZERİNDE ENİNE PULSATİF BİR JET İLE ISI TRANSFERİNİN DENEYSEL İNCELENMESİ

Abstract

Bu çalışmada, düz bir levha üzerinde ısı transferine enine pulsatif bir jetin etkisi deneysel olarak incelenmiştir. Deneysel çalışma bir ısıtıcı ve pulsatif bir jetten oluşmaktadır. Isıtıcı, sabit ısı akısına sahip bakır bir levhadan yapılmış ve rüzgar tünelinin içine yerleştirilmiştir. Pulsatif jet, levha girişinde akış içerisine enjekte edilmektedir. Pulsatif jet, piston-silindir mekanizmasının salınım hareketi ile oluşturulmakta ve ikincil kütle akısı yüksek basınçlı bir fan kullanılarak sağlanmaktadır. Çalışmada, ana akış Reynolds sayısı, pulsatif jet frekansı ve genliği değiştirilirken geometri ve diğer parametreler tüm durumlar için sabit kalmaktadır. Ayrıca, ısı transferi üzerinde bu parametrelerin etkisi analiz edilmektedir. Deneyler, dört farklı genlik, altı farklı frekans ve dört farklı üfleme oranı için gerçekleştirilmiştir. Isı transferi mekanizmasını açıklamak için duman-tel metodu ile akış görüntüleme yapılmış ve anlık akış görüntüleri elde edilmiştir. Yüksek üfleme oranlarında, pulsatif frekans ve genliğin her ikisinin de artması ile yüzey soğutma performansının arttığı gözlemlenmiştir. Elde edilen deneysel sonuçlar boyutsuz parametrelerin bir fonksiyonu olarak verilmiştir.

Keywords

• Pulsatif jet
• Düz levha
• Isı transferi iyileştirme
• Film soğutma

EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER WITH A TRANSVERSELY PULSATING JET ON A FLAT PLATE

Abstract

In this study, the effect of a transversely pulsating jet on heat transfer over a flat plate is investigated experimentally. The experimental study consists of a heater and a pulsating jet. The heater is made of a copper plate, has a constant heat flux, and is located in a wind tunnel. The pulsating jet is injected into the stream at the plate entrance. The pulsating jet is created using an oscillating movement of a piston-cylinder mechanism, and the secondary mass flux is supplied using a high-pressure blower. In the study, the Reynolds number in the main stream, the pulsating jet frequency and amplitude are changed, while the geometry and the other parameters remain constant for all cases. Furthermore, the effect of these parameters on heat transfer is analyzed. The experiments are performed for four different amplitudes and six different frequencies at four different blowing ratios. To explain the heat transfer mechanism, flow visualization is performed using the smoke–wire method, and instantaneous flow images are obtained. It is observed that, the surface cooling performance increases with the increase of both the pulsating frequency and amplitude at high blowing ratios. The calculated experimental results are given as a function of dimensionless parameters.

Keywords

• Pulsating jet
• Flat plate
• Heat transfer enhancement
• Film cooling

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