Habib ASAN, Mete AVCI, Orhan AYDIN, Haydar KÜÇÜK

Analysis of heat and fluid flow in concentric annular square ducts

Bu çalışmada, eşmerkezli halka kesite sahip kare kanallarda ısı ve akış karakteristikleri sayısal olarak incelenmiştir. İç ve dış duvarlarda birbirinden farklı olmak koşuluyla sabit yüzey sıcaklığı öngörülmüştür. Akışın laminer, daimi, hidrodinamik ve ısıl olarak tam gelişmiş ve akışkanın sabit fiziksel özelliklerde olduğu kabul edilmiştir. Kartezyen koordinatlarda ifade edilmiş temel korunum denklemleri kontrol hacim yöntemi kullanılarak ayrıklaştırılmış ve ADI yöntemi ile çözülmüştür. Taşınım ve yayınım terimleri sırasıyla yukarı fark ve merkezi fark yöntemiyle ayrıklaştırılmıştır. SIMPLE algoritmasına dayalı basınç-doğrultman denklemini çözmek için Stone metodu kullanılmıştır. Çözümler hava için elde edilmiştir (Pr=0.7). Hız ve sıcaklık alanları, sürtünme faktörü ve Nusselt sayıları boyut oranına (a/b) bağlı olarak gösterilmiştir. Boyut oranının artışıyla, ısı transferinin iç duvarda önemli düzeyde arttığı, dış duvarda ise azaldığı belirlenmiştir. Elde edilen sonuçlar eşmerkezli halka kesitli dairesel kanal akışı ile karşılaştırılmış ve sonuç olarak mevcut geometri akışında daha düşük ısı transferi ve sürtünme faktörünün oluştuğu ortaya konmuştur.

Eşmerkezli halka kesitli kare kanallarda ısı ve akışkan akışının analizi

A numerical study is conducted on the heat and fluid flow characteristics in an annulus between two concentric square ducts. Inner and outer walls are assumed to be isothermal, but at different temperatures. The flow through the annular duct is assumed to be laminar, steady, and both hydrodynamically and thermally fully developed with constant physical properties. For the Cartesian coordinate system, the governing equations are discretized by using the control volume method and are solved by the ADI method. The upwind scheme and the central difference scheme were employed to represent the convection and diffusion terms, respectively. The Stone’s method was employed to solve the pressure-correction equation based on the SIMPLE Algorithm. Solutions were obtained for air (Pr=0.7). The velocity and temperature fields, the friction coefficients and Nusselt numbers are presented depending on the dimension ratio, a/b. With the increasing dimension ratio, it has been shown that the convective heat transfer is remarkably enhanced at the inner wall, while it becoming worse at the outer wall. The present results are compared with those for an annulus between two concentric cylinders and, finally, it is disclosed that the present or former geometry suggest lower heat transfer rates and friction factors

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