KOMPAKT BİR ISI DEĞİŞTİRİCİSİNDE GRAFEN BAZLI NANO AKIŞKANLARIN EKSERJİ ANALİZİ

Öz

Bu çalışmada, kompakt bir ısı değiştiricide grafen bazlı nanoakışkanların ekserji analizi incelenmiştir. Taban akışkan olarak saf su kullanılarak yapılan deneylerde, hacim konsantrasyonlarının %0.01 ve %0.02’sinde grafen nano-ribon ve grafen oksit nanoakışkanlar kullanılmıştır. Deneyler 36, 40 ve 44 oC akışkan giriş sıcaklıklarında, 0.6, 0.7, 0.8 ve 0.9 m3/h kütlesel debilerde gerçekleştirilmiştir. Tüm sıcaklık ve debi değerleri için yapılan hesaplamalar sonucunda hacimce %0.01 GO nanoakışkanının ekserji verimi değerlerinin kullanılan diğer nanoakışkanların ekserji verimlerinden daha yüksek olduğu bulunmuştur. Ayrıca %0.01 GO için hesaplanan ekserji yıkım değerleri, diğer nanoakışkanlar için hesaplanan ekserji yıkım değerinden daha düşüktür. Nanoakışkanların ekserji verimlerinin, akışkan debilerinin ve ısı değiştiricinin giriş sıcaklığının artmasıyla arttığı sonucuna varılmıştır. Nanoakışkan konsantrasyonlarına göre ekserji verimleri karşılaştırıldığında, akışkan konsantrasyonunun artmasıyla ekserji verimlerinin azaldığı sonucu bulunmuştur. Nanoakışkan akış hızlarının artması ve ekserji veriminin artmasıyla ekserji yıkım değerlerinin de arttığı sonucu elde edilmiştir. Nanoakışkan konsantrasyonları ile ekserji yıkımları karşılaştırıldığında, nanoakışkan konsantrasyonunun artmasıyla ekserji yıkımlarının arttığı sonucuna varılmıştır. GO nanoakışkanın ekserji yıkımındaki artış miktarının GNR'den daha fazla olduğu belirlenmiştir.

Anahtar Kelimeler

• Ekserji
• İkinci yasa analizi
• Nanoakışkan
• Isı değiştiricisi
• Isı transferi iyileştirilmesi
• Grafen.

EXERGY ANALYSIS OF GRAPHENE-BASED NANOFLUIDS IN A COMPACT HEAT EXCHANGER

Öz

In this study, the exergy analysis of graphene-based nanofluids in a compact heat exchanger is examined. In experiments using distilled water as the base fluid, graphene nano-ribbon and graphene oxide nanofluids were used at 0.01% and 0.02% of the volume concentrations. The experiments were carried out at 36, 40, and 44 oC fluid inlet temperatures and 0.6, 0.7, 0.8, and 0.9 m3/h mass flow rates. As a result of the calculations made for all temperature and flow rates, it was found that the exergy efficiency values of 0.01% by volume GO nanofluid were higher than the exergy efficiency of the other nanofluids used. Also, the exergy destruction values calculated for %0.01 GO were lower than the value of exergy destruction calculated for other nanofluids. It was concluded that the exergy efficiencies of nanofluids increased with the increase of the fluid flow rates and the inlet temperature of the heat exchanger. When the exergy efficiencies were compared according to the nanofluid concentrations, it was found that the exergy efficiencies decreased with the increase of the fluid concentration. It was examined that the exergy destruction values also increases with the increase of nanofluid flow rates, as well as exergy efficiency. When the exergy destructions were compared to the nanofluid concentrations, it was concluded that the exergy destructions increased with the increase of the nanofluid concentration. It was determined that the amount of increase in exergy destruction of GO nanofluid was higher than that of GNR.

Anahtar Kelimeler

• Exergy
• Second law analysis
• Nanofluid
• Heat exchanger
• Improving heat transfer
• Graphene.

Kaynakça

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