Heat transfer in two-zone thick-walled pipes with axial varying periodic temperature boundary condition

Yıl 2024, Cilt: 3 Sayı: 2, 110 - 124

Ali Ateş

https://doi.org/10.70700/bjea.1586153

Öz

The combined heat transfer in thick-walled pipes is investigated by also considering axial heat conduction. The problem considers a two-zone infinite pipe. There is a constant outer wall temperature boundary condition in the upstream region of the pipe. In the downstream region, the outer wall temperature is assumed to vary periodically in the axial direction spatially. This problem, where the flow is assumed to be laminar, is solved numerically by the finite difference method. The effects of the basic parameters of wall thickness ratio, Peclet number, wall-fluid thermal conductivity coefficient ratio and wall-fluid thermal diffusivity coefficient ratio on the interface heat flux are investigated. The effects of the axial dimensionless frequency on the results are also taken into account in the studies. The results obtained are highly dependent on the parametric values. It is observed that the wall thickness ratio is more effective than the other parametric values. In addition, it can be said that the pipe wall and fluid axial conduction cause heat transfer to the upper flow region at a non-negligible scale.

Anahtar Kelimeler

Transient conjugate heat transfer, Axially periodic temperature, Thick walled pipes, Heat transfer to upstream region

Eksenel periyodik olarak değişen sıcaklık sınır şartına sahip iki bölgeli kalın cidarlı borularda ısı transferi

Öz

Kalın cidarlı borularda birleşik ısı transferi eksenel ısı iletimi de dikkate alınarak incelenmiştir. Problemde iki bölgeli sonsuz bir boru ele alınmıştır. Borunun üst akış bölgesinde sabit dış duvar sıcaklığı sınır şartı vardır. Alt akış bölgesinde, dış duvar sıcaklığının eksenel yönde mekânsal olarak periyodik bir şekilde değiştiği kabul edilmiştir. Akışın laminer kabul edildiği bu problem sonlu farklar yöntemi ile sayısal olarak çözülmüştür. Cidar kalınlığı oranı, Peclet sayısı, duvar-akışkan ısı iletkenlik katsayısı oranı ve duvar-akışkan ısıl yayılım katsayısı oranı temel parametrelerinin ara yüzey ısı akısı üzerindeki etkileri araştırılmıştır. Çalışmalarda eksenel boyutsuz frekansın sonuçlar üzerindeki etkileri ayrıca dikkate alınmıştır. Elde edilen sonuçlar parametrik değerlere oldukça bağlıdır. Özellikle cidar kalınlığı oranının diğer parametrik değerlere nazaran daha etkili olduğu gözlemlenmiştir. Ayrıca buru cidarı ve akışkan eksenel iletiminin üst akış bölgesine ihmal edilemeyecek ölçekte ısı transferine neden olduğu söylenebilir.

Anahtar Kelimeler

Birleşik ısı transferi, Eksenel periyodik sıcaklık, Kalın cidarlı borular, Üst akış bölgesine ısı geçişi

Kaynakça

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