Scale effects on the hydrodynamics of bubble columns

مقدم أطروحة جامعية

Tuma, Farah Salim Jamil

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم الهندسة الكيمياوية

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2008

الملخص الإنجليزي

The main object of this study is to investigate the influence of the column geometric and operating variables (i.

e., column diameter, superficial gas velocity and liquid viscosity) on the hydrodynamic parameter (i.

e., gas holdup, bubble dynamics and liquid phase axial dispersion coefficient). The experimental work was carried out using different column diameters, (7.5, 15 and 30) cm and different axial positions (30, 60 and 90) cm from the distributor.

The superficial gas velocity was varied in the range 1-10 cm / s, spanning both the homogeneous and heterogeneous flow regimes.

Various liquids covering a broad range of viscosity values are employed which are : Distilled water and Glycerin having concentrations : 20 % , 50% and 65 % were used to simulate the behavior of coalescing viscous liquids .

For all experiments the height of liquid phase was maintained constant at 100 cm from the gas distributor. The experimental data obtained showed that the gas holdup increases linearly with superficial gas velocity at both homogeneous and heterogeneous regimes but the rate of increasing is slower at the heterogeneous one. The bubble rise velocity was found to decrease with increasing superficial gas velocity until a transition point was reached and after that the relationship was linearly increasing, It was observed that with an increase in liquid phase viscosity and increase in column diameters, a decrease in gas holdup and an increase in bubble size were obtained. It was observed that increasing axial position led to an increase in bubble diameter and a decrease in bubble rise velocity. Axial dispersion coefficient which is measured by tracer response technique was found to increase with gas superficial velocity, increases with column diameter, increases with axial position and decreases with liquid viscosity. This work also presents a theoretical analysis that is used to calculate the axial dispersion coefficient.

The measured axial dispersion coefficient was generally consistent with the predictions of the well established correlations from the literature.

The validity of the model was settled by comparing its predication with the objective function of the well-Known empirical correlation formulated by (Hikita and Kikukawa, 1974) .The comparison shows that the present model is statistically significant at a 95% confidence level by using goodness - of - fit test. Also a statistical analysis was performed to get a general correlation for the gas holdup (£s ) as a function of the parameters studied : €g = 0.15325 Fr0.2 % 17 Ga0.09223 Bo-0.0424 Where the correlation coefficient (R) was equal to (0,957) and the absolute error (3.5%).

التخصصات الرئيسية

الكيمياء

الموضوعات

• ديناميكا الموائع
• المفاعلات الكيميائية

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305464