Ahmet KORKMAZ, Semih ÖZEL, Mehmed Rafet ÖZDEMİR

CO2 AKIŞKANININ KAYNAMALI AKIŞ REJİMİNDE ISI TRANSFERİ KATSAYISININ ÇOKLU REGRESYON YÖNTEMİ İLE TAHMİNLENMESİ

Teknolojinin gelişmesi ile performansı artan ve boyutu küçülen elektronik cihazların yaydıkları ısı artmış olup ihtiyaç duyulan soğutma yükü çok yüksek değerlere ulaşmıştır. Bu soğutma yükünü karşılayabilmek için kullanılan geleneksel soğutucu akışkanların performansları, iyi olmasına rağmen küresel ısınma katsayıları ve ozon tabakası hasar potansiyel katsayıları yüksektir. Çeşitli uluslararası protokoller ve antlaşmalarla, bu geleneksel soğutucu akışkanların kullanımlarında küresel çapta kısıtlamaya gidilmiştir. Bu nedenle, araştırmacılar alternatif, çevre dostu soğutucu akışkanlar üzerine çalışmalar yapmaya başlamıştır. CO2 akışkanı zehirli olmaması, küresel ısınma katsayısının 1 olması, ozon tabakası hasar potansiyel katsayısının 0 olması ve kaynamalı akış rejiminde yüksek performans sergilemesi sebebiyle, geleneksel akışkanlara rakip olarak öne çıkmaktadır. Fakat CO2’nin diğer akışkanlardan farklı termo-fiziksel özelliklere sahip olması sebebiyle, literatürde CO2 için kaynamalı akış rejiminde ısı transfer katsayısını yüksek doğruluk oranında veren bir korelasyona rastlanmamıştır. Bu çalışmada, farklı çap borularda, kaynamalı akış rejiminde bulunan CO2 akışkanı ile yapılmış çalışmalardan alınan 1084 satır veri ile çoklu regresyon modeli ile ısı transfer katsayısı tahmini yapılmıştır. Bu amaçla 26 değişken analiz edilmiş ve aralarındaki korelasyon incelenmiştir. Sonuçlar literatüre dayalı olarak tartışılarak öneriler kısmında sunulmuştur.

Anahtar Kelimeler:

çoklu regresyon, ısı transferi, kaynamalı akış, tahmin, CO2

PREDICTION OF HEAT TRANSFER COEFFICIENT OF CO2 IN FLOW BOILING REGIME USING MULTIPLE REGRESSION METHOD

With the development of technology, the performance of electric devices has increased, and their sizes have been miniaturized. Therefore, the heat emitted by these devices has elevated, and this increased required cooling load rates. Although the cooling performance of conventional refrigerants could meet these cooling load rates, their global warming potential and ozone layer depletion coefficients are high. Accordingly, international protocols and agreements have started to restrict these traditional refrigerants globally. Therefore, researchers have begun to work on alternative, environmentally friendly refrigerants. At this point, CO2 refrigerant stands out as a competitor to conventional refrigerants due to its non-toxic feature, low global warming potential value (1), zero ozone layer depletion coefficient, and high performance in the flow boiling regime. However, there is no high-accuracy flow boiling heat transfer coefficient in the literature due to the unique thermophysical properties of CO2. In the current study, 1084 flow boiling heat transfer coefficient data of CO2 for pipes having different diameters were taken from the literature studies. The collected flow boiling heat transfer coefficient data were tried to be predicted with the multiple regression model. For this purpose, 26 variables were analyzed and the correlation between them was examined. The results were discussed based on the literature, and suggestions were presented.

Keywords:

CO2, flow boiling, forecasting, heat transfer, multiple regression.,

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