High Liquid Concentrations Research Articles

Structure of a supersonic gas-liquid jet at high liquid concentrations

Structure of a supersonic gas-liquid jet at high liquid concentrations

"H" sprayer effect on liquid deposition on cucumber leaves and powdery mildew prevention in the shed.

To clarify the effect of droplet size on solution deposition and powdery mildew control on greenhouse cucumber leaves, the effect of volume median droplet diameter (VMD) on solution deposition and maximum retention, as well as the effect of flusilazole on powdery mildew control on cucumber, was determined using the stem and leaf spray method. The VMD of the typical fan nozzles (F110-01, F110-015, F110-02, F110-03) of the selected US Tee jet production differs by approximately 90 μm. The results showed that the deposition of flusilazole solution on cucumber leaves decreased as the VMD of the droplets increased and that the deposition of the solution in the treatments with VMD of 120, 172, and 210 μm decreased by 22.02%, 10.37%, and 46. 97%, respectively, compared to that observed with treatment with 151 μm VMD. The deposition of the solution on cucumber leaves showed the highest deposition efficiency of 63.3% when the applied solution volume was 320 L/hm2, and the maximum stable retention of the liquid on the leaves was 6.6 µl/cm2. The control effects of different concentrations of flusilazole solution on cucumber powdery mildew differed significantly, and the best control effect was achieved at the dosage of 90 g/hm2 of the active ingredient, which was 15%-25% higher than that observed at the dosage of 50 and 70 g/hm2 of the active ingredient per hectare. A significant difference in the effect of droplet size on the control of cucumber powdery mildew was observed at any specific liquid concentration. Nozzle F110-01 showed the best control effect when the dosage of the active ingredient was 50 and 70 g/hm2 per hectare, which did not differ significantly from that observed with nozzle F110-015 but differed significantly from those observed with nozzles F110-02 and F110-03. Hence, we concluded that the use of smaller droplets with VMD of 100-150 μm, i.e. the choice of F110-01 or F110-015 nozzles, for application on the leaf parts of cucumber in the greenhouse under conditions of high liquid concentration, can significantly improve the effective use of pharmaceuticals and the disease control effect.

Drift-diffusive liquid migration in partly saturated sheared granular media

Abstract

Revisiting dynamics and models of microsegregation during polycrystalline solidification of binary alloy

Microsegregation formed during solidification is of great importance to material properties. The conventional Lever rule and Scheil equation are widely used to predict solute segregation. However, these models always fail to predict the exact solute concentration at a high solid fraction because of theoretical assumptions. Here, the dynamics of microsegregation during polycrystalline solidification of refined Al-Cu alloy is studied via two- and three-dimensional quantitative phase-field simulations. Simulations with different grain refinement level, cooling rate, and solid diffusion coefficient demonstrate that solute segregation at the end of solidification (i.e. when the solid fraction is close to unit) is not strongly correlated to the grain morphology and back diffusion. These independences are in accordance with the Scheil equation which only relates to the solid fraction, but the model predicts a much higher liquid concentration than simulations. Accordingly, based on the quantitative phase-field simulations, a new analytical microsegregation model is derived. Unlike the Scheil equation or the Lever rule that respectively overestimates or underestimates the liquid concentration, the present model predicts the liquid concentration in a pretty good agreement with phase-field simulations, particularly at the late solidification stage.

Performance estimation of a venturi scrubber and its application to self-priming operation in decontaminating aerosol particulates

To understand the performance of a venturi scrubber operating in self-priming mode, the present study develops a computational model to simulate the interacting three phase flow occurring in the venturi scrubber. The computational model is based on an Euler- Lagrangian framework where parcels of droplets and aerosols are tracked throughout the flow domain. The model incorporates the effect of droplet collision and increased momentum source in the regions of high liquid concentration. Additionally, the droplet inertial effects on the shear induced multi-jet breakup is included to predict the evolution of the droplet size distribution. The predicted local liquid loading, pressure drop and the collection efficiency were found to be in good match with the cited experimental values. The jet penetration and the droplet mean diameter is combined to form a unique dimensionless number, called the Performance Parameter, to quantify the multi-jet characteristics in the throat section of the scrubber. Higher values of Performance Parameter corresponded to higher efficiencies of the scrubber, hence serves as an analytical tool to assess the performance of the scrubber. Based on the parametric study for different throat gas velocities, liquid injection velocities, changing throat length and changing orifice diameter, the applicability of such a scrubber to self-priming mode is discussed. Further, for transients incurring lower gas velocities and lower operating height, the advantages of multi-stage injection and variable injection diameter are presented.

Agglomerate behavior in a recirculating fluidized bed with sheds: Effect of agglomerate properties

A radioactive particle tracking (RPT) technique was used to study the effect of the size and density of an agglomerate on its interactions with internal baffles in a fluidized bed, mimicking the stripper sheds of a Fluid CokerTM. Dense agglomerates (mimicking Fluid Coker agglomerates with a high liquid concentration) have a lower residence time in the stripper section of the reactor than light agglomerates (mimicking Fluid Coker agglomerates with a low liquid concentration) and small dense agglomerates spend more time in the stripper section than large dense agglomerates. A simple thermal drying model is proposed that uses the particle tracking results to determine the rate of release of hydrocarbons vapors in and below the shed zone, vapors which are responsible for stripper shed fouling. The model predicts that small dense agglomerates dry quickly while large dense agglomerates retain up to 50% of their original liquid when they leave the bed. Up to 18% of the original liquid contained in large dense agglomerates is evaporated and released in and below the shed zone, and thus contributes to shed fouling.

Evaporation of a thin binary liquid film by forced convection into air and superheated steam

This paper deals with a numerical analysis of the evaporation of a thin binary liquid film by forced convection inside a channel constituted by two plates. The first plate is externally insulated and wetted by a thin water ethylene glycol film while the second is dry and isothermal. The first part is concerned with the effects of inlet ambiance conditions and the liquid concentration of ethylene glycol on the distribution of the velocity, temperature, concentrations profiles and the axial variation of the evaporation rate. The second part is focused on the inversion temperature point of the evaporation of binary liquid film. Results show that the inversion temperature phenomenon for the evaporation of binary liquid mixture is observed for high liquid concentration of ethylene glycol. The present results show that in the inlet temperature range considered here, the inversion temperature does not exit for the evaporation of pure ethylene glycol.

Water vapor condensation in forced convection flow over an airfoil

The present paper presents an investigation of water vapor's condensation to liquid substance in highly convective flow conditions. An airfoil geometry was chosen to demonstrate the applicability of the model developed. The flow is considered subsonic and compressible, at high Reynolds number. The contribution of turbulence effects is accounted for by the Spalart–Allmaras model, which is suitable for such type applications. The study of condensation is based on a mixture two-phase model, which allows for interpenetrating substances, while following the economical single-fluid approach. Furthermore, the phases may move at different velocities (slip velocity) in a manner that is described by conservation equations. Results are presented for several flight conditions, concerning the angle of attack and the ambient-air humidity levels. Since the condensation effects are investigated on an airfoil configuration, emphasis has been given to the liquid mass-fraction distribution in several critical areas, where considerable formation of liquid droplets is observed. Results show that for humidity levels higher than 0.7, high liquid concentration areas are indicated onto the rear part of the foil. Attention is focused on the dispersion of the condensation cloud and on the areas of mass-transfer interaction between liquid droplets and humid air.

A model study based on experiments on toluene removal under high load condition in biofilters

As a control measure for substrate inhibition phenomenon in biofilters caused by toxic gases with high concentration, an appropriate mathematical model is required to calculate gas concentrations at various positions within and outside biofilms. Thus validation of the Deshussess model, Devinny–Hodge model and Luong Model were carried out for high toluene load conditions, and the results were examined for their veracity. Calculated concentrations using the modified Deshussess model, which considers sorption volume of carriers, approximated to measurements. This appears to mean the contribution of porosity in inorganic ceramic carriers to the biological removal of toluene vapor. Since toluene removal capacities for high liquid concentrations, which were calculated using the Luong model, approximated to the measurements, the generality and usefulness of the Luong model in predicting the substrate elimination capacity in biofilters with substrate inhibition appear to be manifested. Simplified Devinny–Hodge model turned out to be not applicable to predicting gas concentration along longitudinal axis of biofilters with high gas load. Various model parameters, needed for modeling studies, including critical toluene load per unit biomass and time, maximum toluene degradation rate, half velocity toluene concentration, and maximum toluene concentration in liquid, above which biodegradation is inhibited, were experimentally determined.

The performance of continuous cyclic ion-exchange reactors—II: Reactions with intraparticle diffusion controlled kinetics

This work extends the previous experimental and theoretical study of the Cloete-Streat stage-wise solid-liquid contactor to the case of high liquid concentrations where the rate of ion exchange is limited by the kinetics of intraparticle diffusion. In all cases, the reaction studied was neutralizat fo NaOH with a cationic exchange resin. Experiments were carried out in a three-stage system and simulations using literature values of the kinetic parameters and a population-based model of this system gave excellent agreement (within 27%) with the experimental results. It was found that small improvements beyond steady-state performance could be obtained by varying the fraction of solids periodically transferred, keeping flow rates and mean residence times of both phases constant. However, if solids conversion is high (∼90%), as was unavoidable in these experiments, the scope for such improvement in performance decreases and any inefficiency due to the method of addition of solids can actually lead to a small decrease in the overall performance when compared to that of steady-state.

Diffusion of Liquids in Crosslinked Rubbers

Abstract Diffusion of various liquids in natural rubber vulcanizates has been studied by following the kinetics of the mass uptake of a rubber sheet immersed in the liquid. An anomaly in the mass uptake-time relation is due to stresses set up in the sheet during swelling and to their variation as swelling proceeds. This anomaly has been eliminated by using specimens constrained laterally, by bonding to metal backing plates, which maintains boundary conditions constant during swelling. At the liquid concentrations used, the diffusion coefficient depends mainly on the liquid viscosity rather than compatibility of the rubber and liquid. Neither amount of carbon black filler nor of crosslinking of the rubber has a significant effect on the diffusion coefficient measured at relatively high liquid concentrations.

Diffusion of liquids in crosslinked rubbers. Part 1

The diffusion of various liquids in natural rubber vulcanizates has been studied by following the kinetics of the mass uptake of a sheet of rubber while immersed in the liquid. An anomaly in the mass uptake-time relation is due to the stresses set up in the sheet during swelling and to their variation as the swelling proceeds. This anomaly has been eliminated by using samples constrained laterally, by bonding to metal backing plates, which maintains the boundary conditions constant during the swelling. At the liquid concentrations used, the diffusion coefficient depends mainly on the liquid viscosity rather than the compatability of the rubber and the liquid. Neither the amount of carbon black filler not the degree of crosslinking of the rubber has a significant effect on the diffusion coefficient measured at relatively high liquid concentrations.