Bed-to-surface heat transfer in conical spouted and spout-fluid beds

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Kimya Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2017

Öğrenci: ONUR YAMAN

Danışman: GÖRKEM KÜLAH

Özet:

Bed-to-surface heat transfer investigation from a vertically immersed cylindrical surface was conducted in large laboratory scale conical spouted and spout-fluid beds in this study. In order to design a high performance spouted and spout-fluid beds, the effects of bed design parameters (such as conical angle, inlet diameter of spouting gas entrance) and operating conditions (such as static bed height, particle size and density and spouting and fluidization gas flow rates) on the heat transfer characteristics were investigated in detail. An empirical heat transfer correlation of the average heat transfer coefficients in the annulus section for high-density particles (2500 ≤ ρp ≤ 6000 kg/m3) was also proposed for the practical use in industrial applications. The heat transfer coefficients were found to depend on the density and size of the particles. The denser and larger particles had higher minimum stable spouting velocities, which in turn lead to higher operational spouting velocities resulting in higher heat transfer coefficient values. The effect of particle diameter was more pronounced in the spout and spout-annulus interface whereas its effect diminished in the annulus region. The conical angle had a significant effect on the gas flow distribution and particle-probe contact dynamics in the vi spouted bed and it was observed that the heat transfer values in the annulus decreased with the increase in conical angle due to lowered particle circulation. Benefits of the spout-fluid operation on the heat transfer coefficients were found fairly minor considering maximum of 7 and 3 % increase in heat transfer coefficient observed during spout-fluid operation for 31º and 66º conical angle conical spoutfluid beds, respectively, since the fluidizing gas (Gf) was not able to penetrate sufficiently inside the annulus to maintain an effective gas flow on the heat transfer surface. Therefore, from the heat transfer point of view, given the required flow rates for spout-fluid bed operation, spouted beds were found to be more feasible compared to spout-fluid beds.