Faz Değiştiren Malzemelerle Termal Enerji Depolayan Bir Isı Değiştiricisinin Sayısal Analizi

Bu çalışmada, termal enerji depolama (TED) sistemlerinde kullanılan bir iç içe borulu ısı değiştiricisinde faz değiştiren malzemenin (FDM) erime sürecindeki ısıl davranışı, kanatçıklı ve kanatçıksız modeller ile sayısal analizi yapılarak incelenmiştir. Sayısal analizler, Hesaplamalı Akışkanlar Dinamiği (HAD) yaklaşımını kullanan ANSYS Fluent ticari programı ile iki boyutlu ve zamana bağlı olarak gerçekleştirilmiştir. Öncelikle literatürde mevcut deneysel bir çalışma referans alınarak sayısal analiz kanatçıksız model için doğrulanmıştır. Bu modelde ısı transfer akışkanı (ITA)’nın sıcaklıkları 50 oC, 60 oC ve 70 oC alınarak ITA sıcaklığının FDM erime süresine etkisi değerlendirilmiştir. Daha sonra bu modele 6, 9, 12 ve 15 adet kanatçıklar eklenip, kanatçık sayısının da FDM’nin erime süresine etkisi araştırılmıştır. Yapılan sayısal çalışmada elde edilen sonuçlar, ITA sıcaklığı ve kanat sayısı arttıkça FDM’nin erime süresinin azaldığını, böylece FDM’nin daha hızlı bir şekilde ITA’dan ısıyı depoladığını göstermektedir. Kanat etkenlikleri sırasıyla 2,66, 3,49, 4,32 ve 5,15 olan 6, 9, 12 ve 15 kanatçıklı modellerin kanatçıksız modele göre erime süresini %72,5, %76,7, %78,4 ve %80 azalttığı belirlenmiştir.

Anahtar Kelimeler:

Termal enerji depolama, faz değiştiren malzemeler, erime süresi

Numerical Analysis of a Heat Exchanger That Stores Thermal Energy with Phase Change Materials

In this study, the thermal behavior of the phase change material (PCM) during melting process inside a shell-and-tube heat exchanger used in thermal energy storage (TES) systems has been investigated by numerical analysis with fin and without fin models. Two dimensional transient numerical analyzes have been carried out with the ANSYS Fluent commercial program using the computational fluid dynamics (HAD) approach. The study has been first validated for the without fin model with reference to an experimental study available in the literature. In this model, the effect of temperature of heat transfer fluid (HTF) on PCM melting time has evaluated by taking HTF’s temperatures 50 oC, 60 oC and 70 oC. Then, 6, 9, 12 and 15 fins have been added to this model and the effect of the number of fins on the PCM melting time has been investigated. The results obtained in the numerical study show that as the HTF temperature and number of fins increase, the melting time of PCM decreases, so that PCM stores more rapidly the heat from HTF. It has been determined that the fin models with 6, 9, 12 and 15 which are 2,66, 3,49, 4,32 and 5,15 of fin effectiveness reduce the melting time by 72,5%, 76,7%, 78,4% and 80% respectively, according to without fin model.

Keywords:

Thermal energy storage, phase change materials, melting time,

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