Experimental Investigation of a Non-Uniform Pulsating Heat Pipe Charged by Binary Mixtures at a Low Filling Ratio

Abstract

In this study, thermal performance and flow behavior of flat-plate closed loop pulsating heat pipe having non-uniform channel profile and being charged by binary mixtures at a low filling ratio are experimentally investigated. In the experiments, binary mixtures of ethanol (E) and methanol (M) obtained at different volume mixing ratio (E:M = 1:1, 1:2 and 2:1) are used as working fluid. The filling ratio is kept constant as 20%; while it is studied three different inclination angles as 0o, 45o and 90o. Flow behavior is investigated via simultaneous images obtained by a high speed camera (1000 fps). It is concluded that the volume mixing ratio has a great importance on startup performance, the thermal performance increases with increasing methanol ratio, and the heat pipe can operate at all mixing ratios without the aid of gravity. It is observed that the heat transfer characteristics improve with increasing inclination angle. Through the flow images, physical phenomena in the flow passages are defined.        

Keywords

• Binary mixture
• Thermal performance
• Pulsating heat pipe

Düşük Dolum Oranında İkili Karışımlarla Yüklü Üniform Olmayan Atımlı Isı Borusunun Deneysel İncelenmesi

Abstract

Bu çalışmada, düşük bir dolum oranında ikili karışımlarla yüklü, üniform olmayan kanal profiline sahip düz plakalı kapalı döngülü atımlı bir ısı borusunun ısıl performansı ve akış davranışı deneysel olarak incelenmiştir. Deneyler kapsamında iş akışkanı olarak, etanol (E) ve metanolün (M) farklı hacim oranları (E:M = 1:1, 1:2 ve 2:1) için elde edilen ikili karışımları kullanılmıştır. Dolum oranı %20 olarak sabit tutulmuş olup; 0o, 45o ve 90o olmak üzere üç farklı eğim açısında çalışılmıştır. Akış davranışı yüksek hızlı kamera ile elde edilen eş zamanlı görüntüler üzerinden irdelenmiştir (saniyede 1000 görüntü). Yapılan çalışma sonucunda; karışım oranının çalışmaya başlama performansı üzerinde önemli bir etkiye sahip olduğu; artan metanol oranı ile ısıl performansın arttığı ve ısı borusunun, tüm karışım oranlarında, yer çekimi desteği olmadan da çalışabildiği belirlenmiştir. Isı transfer karakteristiklerinde artan eğim açısıyla iyileşme gözlemlenmiştir. Akış görüntüleri aracılığıyla, akış pasajları içerisindeki fiziksel olaylar tanımlanmıştır.         

Keywords

• İkili Karışım
• Isıl performans
• Atımlı ısı borusu

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