Local Mass Transfer Phenomena and Chemical Selectivity of Gas‐Liquid Reactions in Capillaries

2019 ◽  
Vol 42 (7) ◽  
pp. 1536-1537
Author(s):  
Waldemar Krieger ◽  
Jan Lamsfuß ◽  
Wei Zhang ◽  
Norbert Kockmann
Keyword(s):  
Mass Transfer ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Chemical Selectivity

Method to Visualize Local Mass Transfer and Chemical Selectivity of Gas-Liquid Reaction in Coiled Capillaries

2017 ◽  
Author(s):  
Waldemar Krieger ◽  
Jan Lamsfuß ◽  
Norbert Kockmann
Keyword(s):  
Mass Transfer ◽  
Indigo Carmine ◽  
Volumetric Flow Rate ◽  
Hypodermic Needle ◽  
Concentration Gradients ◽  
Local Mass ◽  
Local Mass Transfer ◽  
On Line ◽  
Gas Liquid Flow ◽  
Chemical Selectivity

Gas-liquid reactions in microstructured devices have recently gained much attention in scientific research and industry. Enhanced heat and mass transfer can be employed to overcome mass transfer limitations in gas-liquid reactions. Helically coiled capillaries can further increase mass transfer due to Dean vortices, which narrow the residence time distribution, too. In this work, a colorimetric technique is implemented in order to visualize local mass transfer phenomena and concentration gradients of gas-liquid reactions in straight and helically coiled capillaries. The method enables on-line and non-invasive investigation of mass transfer and chemical selectivity in microchannels with high spatial resolution. Straight and helically coiled capillaries are fabricated from FEP tubes with inner diameter of 1.6 mm. Bubbles are generated by a hypodermic needle, which is placed in the center of the FEP tube generating a stable slug flow. Total volumetric flow rate is varied from 1.6 to 6.5 mL/min and volume ratios of gas/liquid flow from 0.17 to 6.0. Selectivity experiments are performed with the consecutive oxidation of leuco-indigo carmine.

Local Mass Transfer Phenomena and Chemical Selectivity of Gas-Liquid Reactions in Capillaries

2017 ◽  
Vol 40 (11) ◽  
pp. 2134-2143 ◽  
Author(s):  
Waldemar Krieger ◽  
Jan Lamsfuß ◽  
Wei Zhang ◽  
Norbert Kockmann
Keyword(s):  
Mass Transfer ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Chemical Selectivity

scholarly journals Liquid distribution and its effect on local mass transfer in a packed column of Pall rings

2021 ◽  
Author(s):  
Yongjia Zhu
Keyword(s):  
Mass Transfer ◽  
Gas Flow ◽  
Transfer Coefficients ◽  
Liquid Distribution ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Liquid Distributor ◽  
Wall Flow

The spatial variations of liquid distribution and local mass transfer coefficient in a 0.30-m column of 25.4-m Pall rings were investigated. The data of liquid distribution was collected with a 39-cell liquid collector and a wall-flow tube from a doubled-wall section in the column at the packing-support level. The local mass transfer coefficients were measured via the electrochemical technique by individual cathodic nickel-coated Pall rings placed at various spatial positions. Both measurements were conducted at various fluid flow rates with three liquid distributor designs at different bed heights. Liquid distribution and local mass transfer coefficients observed were far from uniform in the column. The wall flow developed along the packed bed until a fully developed flow pattern was reached. With more uniform initial liquid distribution, the less packing height needed to reach the fully developed flow pattern along with higher the mass transfer efficiency in the column. Ladder-type liquid distributor (LLD) showed less angular effect in measurements. Increasing the liquid flow rate slightly improved the uniformity of liquid distribution and enhanced the mass transfer. No influence of gas flow rate on liquid distribution and mass transfer coefficient was found at the range of gas flow rates used. These gas flow rates were much lower than the loading point. Liquid maldistribution factor and mass transfer maldistribution factor decreased with increases in the uniformity of the initial liquid distribution. These values were 0.21(0.48). 0.16(0.26) and 0.14(0.22) for single-point liquid distributor (SPLD), cross-type liquid distributor (CLD) and LLD, respectively. By comparison, a good agreement was observed on the relation of liquid maldistribution factor and mass transfer maldistribution factor.

scholarly journals Liquid distribution and its effect on local mass transfer in a packed column of Pall rings

2021 ◽  
Author(s):  
Yongjia Zhu
Keyword(s):  
Mass Transfer ◽  
Gas Flow ◽  
Transfer Coefficients ◽  
Liquid Distribution ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Liquid Distributor ◽  
Wall Flow

The spatial variations of liquid distribution and local mass transfer coefficient in a 0.30-m column of 25.4-m Pall rings were investigated. The data of liquid distribution was collected with a 39-cell liquid collector and a wall-flow tube from a doubled-wall section in the column at the packing-support level. The local mass transfer coefficients were measured via the electrochemical technique by individual cathodic nickel-coated Pall rings placed at various spatial positions. Both measurements were conducted at various fluid flow rates with three liquid distributor designs at different bed heights. Liquid distribution and local mass transfer coefficients observed were far from uniform in the column. The wall flow developed along the packed bed until a fully developed flow pattern was reached. With more uniform initial liquid distribution, the less packing height needed to reach the fully developed flow pattern along with higher the mass transfer efficiency in the column. Ladder-type liquid distributor (LLD) showed less angular effect in measurements. Increasing the liquid flow rate slightly improved the uniformity of liquid distribution and enhanced the mass transfer. No influence of gas flow rate on liquid distribution and mass transfer coefficient was found at the range of gas flow rates used. These gas flow rates were much lower than the loading point. Liquid maldistribution factor and mass transfer maldistribution factor decreased with increases in the uniformity of the initial liquid distribution. These values were 0.21(0.48). 0.16(0.26) and 0.14(0.22) for single-point liquid distributor (SPLD), cross-type liquid distributor (CLD) and LLD, respectively. By comparison, a good agreement was observed on the relation of liquid maldistribution factor and mass transfer maldistribution factor.

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