HAVUZ KAYNAMA ISI TRANSFERİNDE MEKANİK ÇALKALAMA ETKİLERİNİN DENEYSEL İNCELENMESİ

Öz

Bu çalışmada, havuz kaynamada ısı transferini iyileştirme metotlarından biri olan mekanik çalkalamanın ısı transfer katsayısına etkisi deneysel olarak araştırılmıştır. Deneysel çalışma kapsamında bir deney düzeneği kurulmuştur. Deney akışkanı olarak saf su kullanılmıştır. Deneylerde havuz içerisinde mekanik çalkantı oluşturmak amacıyla farklı devir hızlarında çalışan bir adet 100 mm çapında aksiyel fan kanadı kullanılmıştır. Deneylerde 100 mm uzunluğunda 20 mm çapında silindirik çelik ısıtıcı kullanılmıştır. Deneyler havuz kaynamada en yüksek ısı transfer katsayılarının elde edildiği kabarcıklı kaynama bölgesinde (su için ∆T 5-30 ºC) gerçekleştirilmiştir. Deneyler 9 farklı ısıtıcı gücünde (17, 23, 29, 38, 47, 58, 70, 83 ve 94 kW/m2) ve 5 farklı mekanik karıştırıcı devrinde (0, 55, 139, 205 ve 212 d/d) gerçekleştirilmiştir. Isı transferi katsayısının, ısıtıcı gücün ve mekanik karıştırıcının devir sayısının artmasıyla arttığı tespit edilmiştir. Isıtıcı gücün 17 kW/m2 den 94 kW/m2 ye yükseltilmesiyle (mekanik karıştırıcının 55 d/d da sabit tutulmuştur), ısı transferi katsayının yaklaşık %10 oranında arttığı belirlenmiştir. Düşük ısıtıcı gücünde (17 kW/m2’de), devir sayısının 0 d/d’dan 212 d/d’ya çıkartılmasıyla, ısı transferi katsayısının %190 oranında iyileştiği tespit edilmiştir.

Anahtar Kelimeler

• Buhar
• Havuz kaynama
• Mekanik karıştırma
• Isı transfer katsayısı

EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER EFFECTS OF MECHANICAL AGITATION IN POOL BOILING

Öz

In this study, the effect of mechanical agitation, which is one of the methods of improving the heat transfer in pool boiling, on the heat transfer coefficient has been investigated experimentally. Pure water has been used as the test fluid. In the experiments, a 100 mm diameter axial fan blade operating at different rotational speeds have been used to create mechanical agitation in the pool. In the experiments, 100 mm long, 20 mm diameter cylindrical steel heater has been used. Experiments have been carried out in nucleate boiling regime region (for water ∆T 5-30 ºC), where the highest heat transfer coefficients have been obtained in pool boiling. Experiments have been carried out at 9 different heating power (17, 23, 29, 38, 47, 58, 70, 83 and 94 kW/m2) and at 5 different mechanical agitator speeds (0, 55, 139, 205 and 212 rpm). It has been determined that the heat transfer coefficient (HTC) increases with the increase of the heater power and the speed of the mechanical agitator. Increasing the heater power from 17 kW / m2 to 94 kW / m2 (the mechanical agitator has been kept constant at 55 rpm), it has been determined that the heat transfer coefficient increased by approximately 10%. It has been determined that the HTC improved by 190% by increasing the number of revolutions from 0 rpm to 212 rpm at low heater power (at 17 kW/m2).

Anahtar Kelimeler

• Pool boiling
• Mechanical agitation
• Heat transfer coefficient
• Vapor

Kaynakça

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