Düşey kanalda piezoelektrik fanın doğal taşınım üzerindeki dinamik etkileri

Öz

Bu çalışmada yanal duvarları sabit sıcaklıkta tutulan düşey bir kanal içerisine yerleştirilen piezoelektrik fanın (piezo fan) dinamik ısı transfer karakteristikleri sayısal olarak incelenmiştir. Piezofanın bir ucu konsol fan gibi sabitlenmiş olup, diğer ucu dört farklı genlik ve üç farklı frekansta salınım hareketi gerçekleştirmektedir. Kanal içindeki sıcaklık dağılımları, basınç değişimleri ve girdapların dinamik mekanizmaları araştırılacak şekilde fanın genliği farklılaştırılmıştır. Sayısal çalışmalar COMSOL Multiphysics yazılımında 2 boyutlu model kullanılarak gerçekleştirilmiştir. Kanal içerisindeki doğal taşınım referans durum olarak ele alınmıştır. Piezo fanın hareketi, akış yönü boyunca yüksek hızda girdaplar oluşturarak bunları duvar yüzeylerine itmektedir. Bu tür karmaşık taşınım mekanizmaları ısıtılan duvardan gerçekleşen ısı transferini olumlu yönde etkilemektedir. Ele alınan tüm durumlar için yerel ve ortalama ısı transfer katsayıları ve Nusselt sayıları karşılaştırmalı olarak sunulmuştur. Sonuç olarak 12 mm genlik ve 20 Hz frekansta çalışan piezoelektrik fanın, doğal taşınıma göre %169 ısı transfer iyileştirmesi ile en etkili tasarım olduğu belirlenmiştir. En yüksek genlik ve frekans için kütlesel debideki artış ise %180 olarak elde edilmiştir.

Anahtar Kelimeler

• Piezoelektrik fan
• Salınımlı fan
• Doğal taşınım
• Girdap oluşumu

Dynamic effects of piezoelectric fan on the natural convection in a vertical channel

Öz

In this study, the dynamic heat transfer characteristics of a piezoelectric fan (piezo fan) placed in a vertical channel with constant temperature side walls were investigated numerically. One of the piezo fan’s ends is fixed like a cantilever fan, and the other end performs oscillation motion at four different amplitudes and three different frequencies. The operating amplitude of the fan has been varied in such a way as to investigate the temperature distributions, pressure variations, and dynamic mechanisms of the vortices inside the channel. Numerical studies were carried out using a 2-dimensional model in the COMSOL Multiphysics software. Pure natural convection inside the channel is considered as a reference case. The piezo fan’s movement creates high-speed vortices along the flow direction, pushing them onto wall surfaces. Such complex convective mechanisms positively affect heat transfer through the hot wall. Each case’s local and average heat transfer coefficients and Nusselt numbers are compared. As a result, the piezoelectric fan operating with 12 mm amplitude and 20 Hz frequency was determined to be the most effective design with a heat transfer improvement of 169% compared to the natural convection. For the highest amplitude and frequency, the increment in the mass flow rate is up to 180%.

Anahtar Kelimeler

• Piezoelectric fan
• Oscillating fan
• Natural convection
• Vortex generation

Kaynakça

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