Liquid distribution in trickle‐bed reactors

Gas–liquid two-phase flow distributions in parallel channels for fuel cells

The most of past studies in foaming trickle bed reactors aimed at the improvement of efficiency and operational parameters leads to high economic advantages. Conventionally most of the industries rely on frequently used gas continuous flow (GCF) where operational output is satisfactory but not yields efficiently as in pulsing flow (PF) and foaming pulsing flow (FPF). Hydrodynamic characteristics like regime transitions are significantly influenced by foaming nature of liquid as well as gas and liquid flow rates. This study?s aim was to demonstrate experimentally the effects of liquid flow rate, gas flow rates and liquid surface tension on regime transition. These parameters were analyzed for the air-aqueous Sodium Lauryl Sulphate and air-water systems. More than 240 experiments were done to obtain the transition boundary for trickle flow (GCF) to foaming pulsing flow (PF/FPF) by use excessive foaming 15-60 ppm surfactant compositions. The trickle to pulse flow transition appeared at lower gas and liquid flow rates with decrease in liquid surface tension. All experimental data had been collected and drawn in the form of four different transitional plots which are compared and drawn by using flow coordinates proposed by different researchers. A prominent decrease in dynamic liquid saturation was observed especially during regime transitional change. The reactor two phase pressure evident a sharp rise to verify the regime transition shift from GCF to PF/FPF. Present study reveals, the regime transition boundary significantly influenced by any change in hydrodynamic as well as physiochemical properties including surface tension.

Hydrodynamics characteristics of HDS trickle bed test reactor

Liquid flow distribution has been a major concern when scaling up random packed columns. This study concerns the measurements of liquid flow distribution in a large scale column packed with 25.4 mm stainless steel Pall rings. The liquid flow distribution was studied with packed bed height from 0.9 to 3.5 m, liquid flow rate from 2.91 to 6.66 kg/m2·s, and gas flow rate from 0 to 3.0 kg/m2·s. In addition, three systems, water/air, aqueous detergent solution/air and Isopar/air, were used to study the effect of liquid physical properties on liquid flow distribution, and two different liquid distributors were employed to test the effect of liquid distributor design. It was found that liquid flow distribution was strongly influenced by liquid distributor design, packed bed height, gas flow rate and liquid viscosity, slightly influenced by liquid flow rate, but not by liquid surface tension.

Cocurrent gas—liquid flow in packed columns

One of the most important advantages of twin-fluid atomizers over other atomizers is the opportunity of atomizing liquids in a wide range of liquid properties efficiently. Thus, the fundamentals of spray dynamics, such as spray pattern, liquid breakup length, and spatial droplet size evolution using different liquid properties need to be investigated in some detail. The purpose of this study is therefore to examine and describe the influence of the liquid viscosity and surface tension on the spray performance of prefilming air-blast atomizers. A high-speed background shadowgraphy technique associated with particle tracking and Phase Doppler Anemometry (PDA) as a non-intrusive high-resolution local measurement technique were utilized to study the atomization process regarding the influence of the liquid properties on the spray quality. Generally, the break up mechanism is considerably influenced by the liquid viscosity. The breakup length ( ) is dependent on liquid viscosity with for Pa = 0.25 and 0.6 bar air pressure, respectively. Droplet size distribution profiles of different liquids in axial and radial directions are studied. No significant influences of the surface tension and viscosity were observed on the mean droplet velocity downstream of the spray. A minor increase of the droplet mean diameter was observed with liquid viscosity variations from 22 to 111 mPas, however, the liquid surface tension was verified to play an important role in the atomization process at prefilming airblast atomizers as well. According to the available experimental data, it has subsequently been possible to develop an original and descriptive model based on a dimensional approach at different air pressure ranges.

In this study, we investigated the effect of liquid viscosity and surface tension for inkjet printing on porous cellulose sheets. We used five model liquids, representing the operational field of an industrial high speed inkjet printer, as specified by Ohnesorge- and Reynolds number. Drops with 30 pl and 120 pl drop size were jetted with a commercial HSI printhead. We printed on four uncoated papers representing the most relevant grades on the market in terms of hydrophobisation and surface treatment. We are presenting a quantitative analysis of viscosity and surface tension on the print outcome, evaluating dot size, liquid penetration (print through) and surface coverage of the printed dots. The most important finding is that for liquids within the jetting window the variation of the liquid viscosity typically has a 2–3 times higher impact on the print outcome than variation of the liquid surface tension. Increased viscosity in all cases reduces dot area, liquid penetration and liquid surface coverage. Surface tension plays a smaller role for liquid spreading and penetration, except for hydrophobised substrates, where both are reduced for higher surface tension. Interestingly, higher surface tension consistently increases liquid surface coverage for all papers and drop sizes. A detailed analysis on the competing effect of dot spreading and liquid penetration is presented, in terms of viscosity, surface tension and surface coverage of the liquid.

Electric contribution to the surface tension of a dielectric liquid containing ions

Experimental study on the spray characteristics of an internal-mixing gas-liquid injector

Gas absorption in a centrifugal reactor: hydrodynamics

The present study provides experimental data for the liquid viscosity and surface tension of cyclohexane at or close to saturation conditions by surface light scattering between (280 and 473) K. By applying the hydrodynamic theory for surface fluctuations at the vapor–liquid phase boundary, which could be verified experimentally, the liquid viscosity and surface tension were determined simultaneously at macroscopic thermodynamic equilibrium with average relative expanded (k = 2) uncertainties of Ur(η′) = 0.020 and Ur(σ) = 0.012. For both properties, the present measurement results agree well with reference values in the literature which are restricted to a maximum temperature of 393 K for viscosity and 337 K for surface tension. The experimental results from this work contribute to an improved database for the viscosity and surface tension of cyclohexane over a wide temperature range from a temperature close to the melting point up to 473 K.

Surface tension is a crucial property of liquids that depends on the liquid's composition. This study aims to compare the surface tension of water, chloroform, and acetone using the capillary rise method. It involves using a capillary tube with a known radius, dipping it vertically into a liquid, and measuring the height to which the liquid rises in the tube. The surface tension of the liquid can then be measured experimentally. This relates to height of the liquid in the tube, the radius of the tube, and the surface tension of the liquid. The height of the liquid in the tube is dependent on the radius of the tube, with a smaller radius resulting in a greater height. The surface tension of the liquid is inversely related to the radius of the capillary tube.

In this situation, the influence of surface tension of liquid on the bubble’s acoustic scattering is studied when the surface tension of liquid is equivalent to the static pressure of liquid. The continuity equation of velocity and pressure in the bubble’s surface is established, and the bubble’s surface tension of liquid is introduced into the continuity equation. We got the scattering coefficient and the scattering sound power of a single bubble in a symmetric vibration mode, and further deduced the equivalent incident sound field in the case of multi-bubble conditions. Numerical analysis shows that spherical bubble radius is about 10-6m when the surface tension equivalent to the liquid static pressure, in this case, the influence of bubble’s surface tension of liquid on the scattering coefficient and the scattering sound power of the single bubble can be shown when the angular frequency of the driving acoustic pressure is less than 105 rad/s. In the case of multiple bubbles, it will have a greater impact on the sound pressure amplitude of the equivalent incident sound field. While the influence will not appear clearly if the angular frequency of the driving acoustic pressure is bigger than 105 rad/s. For the acoustic scattering problem of bubbles, it bases on the specific issue to choose whether the surface tension of liquid should be taken into consideration.

Dynamic tank-in-series modelling and simulation of gas-liquid interaction in trickle bed reactor designed for gas fermentation

Free surface synthetic schlieren (FS-SS) is a liquid surface topography visualization technique relying on apparent dot pattern displacement due to liquid surface deformation. It has gained attention in the fluid visualization field due to its relatively simple and inexpensive setup. One of the most powerful features of the FS-SS technique is the 3D topography of deformed liquid surface, in which submillimeter scale changes can be readily observed in great detail. The visualization of liquid meniscus at the solid interface is proposed in this study to calculate surface tension by equating the surface tension force with weight of light, floating object with circular geometry. It was found that surface tensions of liquids are much greater than anticipated, suggesting that the effect of buoyant force of displaced liquid due to deformed interface cannot be neglected. When the buoyant force is included, the calculated surface tension of liquids are within 10% of the reference values.