Düz tüp içerisinde burulmuş şerit kullanarak ısı geçişinin iyileştirilmesi

Yıl 2019, , 251 - 260, 12.03.2019

İbrahim Halil Yılmaz , Taha Tuna Göksu

https://doi.org/10.17798/bitlisfen.462169

Cited By: 5

Öz

Tüp içerisinde ilave parça kullanımı, hidrolik kayıp zafiyeti
pahasına taşınım ısı geçişi katsayısını arttırmak için kullanılan tekniklerden
biridir. İlave parça geometrisinin ve akış koşullarının güçlü bir işlevi olan bu
müşterek etki, toplam sistem performansını iyileştirmek için ayrıntılı şekilde
analiz edilmelidir. Bu çalışma, ısıtma/soğutma elemanı kompaktlığının önemli
olduğu soğutma uygulamalarında sıkça kullanılan düz tüpe (13 mm çaplı ve 1200
mm uzunluğunda) burulmuş şerit ilavesi akabinde termo-hidrolik özelliklerinin
analizi için sayısal bir araştırma sunmaktadır. Burma oranının termo-hidrolik
performans üzerindeki etkisi, soğutma uygulamalarının genelinin çalıştığı 5.025−14.871
Reynolds sayısı aralığında incelenmiştir. Benzetim sonuçlarının doğrulanması deneye
dayalı Dittus-Boelter denklemi ile karşılaştırılmış (düz tüp için) ve iyi bir uyum
elde edilmiştir. Sonuçlar, 6−9 arası burma oranındaki değişimin belirtilen
çalışma koşullarında düz tüpe göre sürtünme faktörünü ve Nusselt sayısını
sırasıyla %197−245, %180−220, %163−189 ve %156−179 ve %32−54, %28−46, %28−33 ve
%28−33 arttırdığını göstermektedir. Hidrodinamik kuvvetlere karşı ısı geçiş
miktarının artırılmasının ölçütü olan performans değerlendirme ölçütü, burma
oranı artışına bağlı olarak 0.90−1.02, 0.89−1.00, 0.91−0.96 ve 0.92−0.96 arasında
değişmiştir. Performans değerlendirme ölçütündeki maksimum artış, en düşük
Reynolds sayısı ve burma oranında elde edilmiştir. Performans değerlendirme
ölçütü Reynolds sayısının artışıyla azalmakta ancak burma oranı arttırılarak yükseltilebilmektedir. 

Anahtar Kelimeler

Isı geçişi iyileştirme, Burulmuş şerit, Burma oranı, Performans değerlendirme ölçütü

Enhancement of heat transfer using twisted tape insert in a plain tube

Öz

The use of insert
within a tube is one of the techniques enhancing the convective heat transfer
coefficient at the expense of hydraulic loss penalty. This mutual effect which
is a strong function of insert geometry and flow conditions is to be analyzed
in detail to improve the overall system performance. This study presents a numerical investigation for
analyzing the thermo-hydraulic characteristics of twisted tape insert in a
plain tube (with a 13-mm-diameter and 1200-mm-long) which is widely used in
refrigeration applications where the compactness of heating/cooling element is significant.
The effect of twist ratio on the thermo-hydraulic performance was conducted for
the Reynolds number range of 5,025−14,871 where most of refrigeration applications
are operated in. The verification of the simulation results was compared to Dittus-Boelter
empirical equation (for the plain tube case) and good agreement was obtained. Results
indicate that the variation of the twist ratio between 6−9 increases the
friction factor and Nusselt number 197−245%, 180−220%, 163−189% and 156−179%,
and 32−54%, 28−46%, 28−33% and 28−33% relative to the plain tube case,
respectively for the specified operating conditions. The performance evaluation
criteria, which are measure of enhancing heat transfer against hydrodynamic
forces, changed between 0.90−1.02, 0.89−1.00, 0.91−0.96 and 0.92−0.96 based on
the twist ratio rise. The maximum enhancement in the performance evaluation criteria
was obtained at the lowest Reynolds number and twist ratio. The performance evaluation
criteria lower with increasing Reynolds number but can be increased by increasing
the twist ratio.

Anahtar Kelimeler

Heat transfer enhancement, Twisted tape, Twist ratio, Performance evaluation criteria

Kaynakça

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