Abstract
A gas-liquid Taylor bubble flow occurs in small diameter channels in which gas bubbles are separated by slugs of pure liquid. This type of flow regime is well suited for solid catalyzed gas-liquid reactors in which the reaction efficiency is a strong function of axial dispersion in the regions of pure liquid. This paper presents an experimental study of liquid phase axial dispersion in a Taylor bubble flow developed in a horizontal tube using high speed photography and radiotracer residence time distribution (RTD) analysis. A parametric dependence of axial dispersion on average volume fraction of gas phase was also investigated by varying the relative volumetric flow rates of the two phases. 137m Ba produced from a 137 Cs/ 137m Ba radionuclide generator was used as radiotracer and measurements were made using the NaI(Tl) scintillation detectors. Validation of 137m Ba in the form of barium chloride as aqueous phase radiotracer was also carried out. Axial Dispersion Model (ADM) was used to simulate the hydrodynamics of the system and the results of the experiment are presented. It was observed that the system is characterized by very high values of Peclet Number (Pe∼10 2 ) which reveals an approaching plug type flow. The experimental and model estimated values of mean residence times were observed in agreement with each other.
Highlights
The two-phase gas-liquid flow in tubes is very important in process engineering operations
If the gas moves in the form of large bubbles separated by liquid slugs which contains small gas bubbles, the flow is attributed as slug flow
The flow pattern in a tube characterized by bubbles separated from one another by liquid phase slugs, and from the channel walls by a thin liquid film with no gas entrained is referred as the Taylor bubble flow
Summary
The two-phase gas-liquid flow in tubes is very important in process engineering operations. The flow pattern in a tube characterized by bubbles separated from one another by liquid phase slugs, and from the channel walls by a thin liquid film with no gas entrained is referred as the Taylor bubble flow. For countries that do not possess radioisotope production facilities, it is necessary to import the radiotracers and long time involved in this process rules out the possibility of achieving potential benefit of this technology Medical radionuclide generators such as 99Mo/99mTc and 113Sn/113mIn provide a partial solution to the problem but radiotracers from these generators have limited applications in industry because of their low gamma energies and adsorption on solid surfaces depending on the chemical and physical conditions. A parametric dependence of axial dispersion on average volume fraction of gas phase was investigated by varying the relative volumetric flow rates of the two phases
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