Hydrodynamic characteristics of gas-liquid beds in contactors with ejector-type gas distributors

1982 ◽  
Vol 47 (7) ◽  
pp. 1939-1949 ◽  
Author(s):  
Jindřich Zahradník ◽  
František Kaštánek ◽  
Jan Kratochvíl ◽  
Milan Rylek
Keyword(s):  
Energy Dissipation ◽  
Energy Dissipation Rate ◽  
Gas Holdup ◽  
Nozzle Geometry ◽  
Hydrodynamic Characteristics ◽  
Gas Distributor ◽  
Liquid Dispersion ◽  
Interfacial Mass Transfer ◽  
Ejector Nozzle ◽  
Nozzle Type

The effect of ejector-nozzle geometry on gas holdup and on the rate of interfacial mass transfer characterized by values of kLa was studied in a tower reactor with ejector-type gas distributor. It has been established that both gas holdup and kLa values are, in contactors of this type, unambiguously determined by the rate of energy dissipation in the place of gas-liquid dispersion formation i.e. in the ejector. No effect of nozzle type and geometry was observed on the character of dependences of gas holdup and kLa on the energy dissipation rate and consequently on the values of coefficients of empirical exponential-type relations used for experimental data correlation.

Gas holdup and interfacial mass transfer in gas-liquid tower contactors with ejector-type gas distributors

1985 ◽  
Vol 50 (11) ◽  
pp. 2535-2544 ◽  
Author(s):  
Jindřich Zahradník ◽  
Jan Kratochvíl ◽  
Milan Rylek
Keyword(s):  
Gas Holdup ◽  
Energy Utilization ◽  
Dissipated Energy ◽  
Favourable Effect ◽  
Experimental Conditions ◽  
Gas Distributor ◽  
Interfacial Mass Transfer ◽  
Tube Type ◽  
Gas Suction ◽  
Nozzle Type

The effect of decisive construction parameters of ejectors on gas holdup and on the rate of interfacial mass transport (characterized by kLa values) was studied in a gas-liquid tower reactor (I.D. 0.3 m) with an ejector (Venturi-tube type) gas distributor. The selected ejector characteristics included diffuser length and angle of diffuser walls inclination as well as nozzle type and geometry. Experimental data confirmed validity of our previously published conclusions on the relation between the rate of energy dissipation in the place of dispersion formation (i.e. in the ejector) and gas holdup and kLa values. The efficiency of dissipated energy utilization was however significantly influenced by the diffuser geometry. According to our experimental evidence the increase of ejector energy effectiveness with increasing diffuser length can be ascribed solely to its favourable effect on the gas suction rate while the mechanism of phases mixing (dispersion formation) in ejector was apparently independent of diffuser geometry within the whole range of experimental conditions.

Design of Venturi-tube gas distributors for bubble-type reactors

1984 ◽  
Vol 49 (9) ◽  
pp. 1939-1948 ◽  
Author(s):  
Milan Rylek ◽  
Jindřich Zahradník
Keyword(s):  
Experimental Data ◽  
Gas Holdup ◽  
Venturi Tube ◽  
Design Parameters ◽  
Dispersion Characteristics ◽  
Liquid Circulation ◽  
Bed Porosity ◽  
Gas Distributor ◽  
Liquid Dispersion

The effect of individual parts of a Venturi-tube gas distributor on quality of the gas-liquid dispersion formed was studied in a bubble-type reactor with forced liquid circulation. Gas holdup (bubble-bed porosity) was used as the dispersion characteristics, type and geometry of nozzles, suction chamber arrangement, and dimensions of the mixing tube and diffuser were chosen as variable design parameters. Experimental data of gas holdup presented in dependence on the rate of energy dissipation in the place of dispersion formation characterized then the dispersion efficiency of the Venturi tube at given conditions. Recommendations for design of Venturi-tube gas distributors are presented based upon the results of the study.

Energy dissipation rate in a baffled vessel with pitched blade turbine impeller

1991 ◽  
Vol 56 (9) ◽  
pp. 1856-1867 ◽  
Author(s):  
Zdzisław Jaworski ◽  
Ivan Fořt
Keyword(s):  
Energy Dissipation ◽  
Cross Sections ◽  
Mechanical Energy ◽  
Vessel Diameter ◽  
Energy Dissipation Rate ◽  
Mean Velocity ◽  
Agitated Vessel ◽  
Radial Profiles ◽  
Pitched Blade Turbine ◽  
Turbine Impeller

Mechanical energy dissipation was investigated in a cylindrical, flat bottomed vessel with four radial baffles and the pitched blade turbine impeller of varied size. This study was based upon the experimental data on the hydrodynamics of the turbulent flow of water in an agitated vessel. They were gained by means of the three-holes Pitot tube technique for three impeller-to-vessel diameter ratio d/D = 1/3, 1/4 and 1/5. The experimental results obtained for two levels below and two levels above the impeller were used in the present study. Radial profiles of the mean velocity components, static and total pressures were presented for one of the levels. Local contribution to the axial transport of the agitated charge and energy was presented. Using the assumption of the axial symmetry of the flow field the volumetric flow rates were determined for the four horizontal cross-sections. Regions of positive and negative values of the total pressure of the liquid were indicated. Energy dissipation rates in various regions of the agitated vessel were estimated in the range from 0.2 to 6.0 of the average value for the whole vessel. Hydraulic impeller efficiency amounting to about 68% was obtained. The mechanical energy transferred by the impellers is dissipated in the following ways: 54% in the space below the impeller, 32% in the impeller region, 14% in the remaining part of the agitated liquid.

Effect of gas distributor on gas–liquid dispersion and mass transfer characteristics in stirred tank

2019 ◽  
Vol 145 ◽  
pp. 314-322 ◽  
Author(s):  
Baoqing Liu ◽  
Qing Xiao ◽  
Ning Sun ◽  
Pengfei Gao ◽  
Fangyi Fan ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Stirred Tank ◽  
Transfer Characteristics ◽  
Gas Distributor ◽  
Liquid Dispersion

scholarly journals Spectral characteristics of spring arctic mesosphere dynamics

1998 ◽  
Vol 16 (12) ◽  
pp. 1607-1618 ◽  
Author(s):  
C. M. Hall ◽  
A. H. Manson ◽  
C. E. Meek
Keyword(s):  
Energy Dissipation ◽  
Middle Atmosphere ◽  
Spectral Characteristics ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Spectral Signature ◽  
Upper Limits ◽  
Waves And Tides ◽  
Signal Fading ◽  
Mf Radar

Abstract. The spring of 1997 has represented a stable period of operation for the joint University of Tromsø / University of Saskatchewan MF radar, being between refurbishment and upgrades. We examine the horizontal winds from the February to June inclusive and also include estimates of energy dissipation rates derived from signal fading times and presented as upper limits on the turbulent energy dissipation rate, ε. Here we address the periodicity in the dynamics of the upper mesosphere for time scales from hours to one month. Thus, we are able to examine the changes in the spectral signature of the mesospheric dynamics during the transition from winter to summer states.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides).

The evolution of turbulent bursts: the b—ε model

1994 ◽  
Vol 5 (4) ◽  
pp. 537-557 ◽  
Author(s):  
M. Bertsch ◽  
R. Dal Passo ◽  
R. Kersner
Keyword(s):  
Partial Differential Equations ◽  
Energy Dissipation ◽  
Energy Density ◽  
Differential Equations ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Self Similar ◽  
Similar Solutions ◽  
Semi Empirical

We study the semi-empirical b—ε model which describes the time evolution of turbulent spots in the case of equal diffusivity of the turbulent energy density b and the energy dissipation rate ε. We prove that the system of two partial differential equations possesses a solution, and that after some time this solution exhibits self-similar behaviour, provided that the system has self-similar solutions. The existence of such self-similar solutions depends upon the value of a parameter of the model.

Sign in / Sign up

Export Citation Format

Share Document