DÜŞEY DUVARLARI KISMİ ISITILAN VE SOĞUTULAN DUVARLAR İÇERİSİNDEKİ SUYUN 4°C CİVARINDAKİ DOĞAL TAŞINIMI

Bu çalışmada, iki boyutlu kavite içerisindeki zamana bağlı ısı transferi prosesi sayısal olarak incelenmiştir. Sayısal model kontrol hacimleri yaklaşımı kullanılarak C++ programlama dilinde oluşturulmuştur. Sayısal kodun doğruluğunu belirlemek için, literatürden alınan sayısal analiz sonuçları ve deneysel hız ölçümleri ile karşılaştırmalar yapılmıştır. Bundan sonra, çeşitli kavite görünüm oranları ve farklı ısıl sınır koşulları için zamana bağlı yerel ve ortalama Nusselt sayısı değişimleri ortaya koyulmuştur. Farklı sınır koşulları ile sıcaklık ve hız dağılımları arasındaki etkileşim incelenmiştir. Soğu depolama uygulamalarında su sıcaklığı yoğunluk dönüşüm sıcaklığının altına düşmekte ve suyun doğal taşınımı kompleks hale gelmektedir. Bununla beraber, literatürde soğu depolama ünitelerinin simülasyonu için geliştirilen modellerin büyük çoğunluğunda birleşik yönetici denklemlerin karmaşıklığını basitleştirmek adına ısı transferi mekanizması iletime indirgenmekte ve böylece çözüm süresinde önemli avantajlar elde edilebilmektir. Karmaşık taşınım akımlarının ihmal edilmesi hatalı tahminlere sebep olabilmektedir. Bu bağlamda, bu çalışmada elde edilecek sonuçlar, depolama ortamı olarak su kullanılan soğu depolama uygulamalarında çalışan araştırmacılara ve tasarım mühendislerine yol gösterici olacaktır.

NATURAL CONVECTION OF WATER NEAR 4°C INSIDE PARTIALLY HEATED AND COOLED VERTICAL WALLS

In this study, transient heat transfer process inside a two-dimensional cavity has been numerically investigated. Thenumerical model has been created with control volume approach by using C++ programming language. In order to determine theaccuracy of the numerical code, comparisons are made with the results of the numerical analysis and experimental velocitymeasurements from the literature. After that, the time-dependent variations of local and averageNusselt numbers have been revealedfor various aspect ratios and different thermal boundary conditions of the cavity. The interaction of temperature and velocitydistributions by different boundary conditions has been examined. In cold storage applications, water temperature decreases belowthe density inversion temperature and the natural convection of water becomes more complicated. Nevertheless, the majority of themodels that are developed to simulate the cold storage units in the literature reduce the heat transfer mechanism into conductionmode to simplify the complexity of the coupled governing equations, so that take advantage of decreasing the computational time.Neglecting the complex convection currents may lead erroneous predictions. In this regard, the results of the current work will guidethe researchers and the design engineers working on the cold storage applications with water as a storage medium.Keywords: Transient natural convection, Density inversion, Partial heating/cooling, Aspect ratio.

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