Initial Liquid Volume Research Articles

A study of the influence of initial liquid volume on the capillary flow in an interior corner under microgravity

In this work the influence of initial liquid volume on the capillary flow in an interior corner is studied systematically by microgravity experiments using the drop tower, under three different conditions: the Concus–Finn condition is satisfied, close to and dissatisfied. The capillary flow is studied by discussing the movement of tip of the meniscus in the corner. Experimental results show that with the increase of initial liquid volume the tip location increases for a given microgravity time, the achievable maximum tip velocity increases and the flow reaches its maximum tip velocity earlier. However, the results for the three different conditions show some difference.

Purification and concentration of a rhamnolipid biosurfactant produced by Pseudomonas aeruginosa SP4 using foam fractionation

Pseudomonas aeruginosa SP4 was cultivated to produce a rhamnolipid biosurfactant from a nutrient broth with palm oil. The foam fractionation technique in batch mode was used for the recovery of the excreted biosurfactant from the free-cell culture medium. The effects of air flow rate, initial foam height, the pore size of the sintered glass disk, initial liquid volume, and operation time on the process performance were studied. The results showed that the operating conditions were optimized at an air flow rate of 30 ml/min, an initial foam height of 60 cm, a pore size of the sintered glass disk in the range of 160–250 μm (No. 0), an initial liquid volume of 25 ml, and an operation time of 4 h, providing a biosurfactant recovery of 97% and an enrichment ratio of 4. The HPLC results also indicated that the rhamnolipid was concentrated by using the foam fractionation technique.

Analysis of a rapid supercritical extraction aerogel fabrication process: Prediction of thermodynamic conditions during processing

Aerogels have unusual mechanical and thermal properties that render them useful in a range of applications from thermal insulators to chemical sensors. However, aerogel fabrication can be difficult, typically requiring the use of supercritical extraction of solvent from the sol–gel matrix. We employ a rapid supercritical extraction (RSCE) technique for aerogel fabrication that is faster and simpler than the standard methods. This technique relies on a hydraulic hot press to heat the chemical precursors and provide the required temperature and pressure increase needed to reach a supercritical state within a contained mold. Experimental results show that the pressure–temperature curve is characterized by a ‘take-off point’ and a ‘leak point’. The take-off point occurs at the start of a rapid increase in pressure and the leak point occurs where the pressure increase subsides. This paper presents an analytical model that predicts the pressure–temperature relationship of the aerogel precursors during the RSCE fabrication process and shows that the model can be extended to other RSCE systems. Using pure methanol, water and aerogel precursors in separate tests, the effects of initial liquid volume and press force on the pressure and temperature during processing were studied. We find that the take-off point can be estimated using a maximum specific volume model, which is a function of the initial percent volume fill of liquid used in the test. We are also able to predict the rapid pressure increase region observed during the process using a constant volume model. Leaking is determined to be a function of the mechanical forces acting on the system and occurs when the pressure in the contained mold nears the value of the pressure imparted onto the gasket by the hot press. The leak point pressure is found to be independent of the initial percent volume of liquid used in the test; however the leak point temperature decreases with increasing initial percent volume fill.

Pulsed dispersion as the critical regime of destruction of a liquid volume

An experimental study is performed to consider the processes of pulsed dispersion of liquid volumes in a wide range of geometric and physical parameters of a system including a cylindrical liquid volume and a loading cylindrical charge of a high explosive located on the axis of symmetry of the liquid volume. Based on an analysis of experimental data, dependences of the dynamics of the size of the expanding gas-droplet cloud, disperse composition, and time of droplet fragmentation in the cloud on the initial parameters of the system are constructed. An analytical dependence determining the relative volume distribution of the droplet size in the cloud being formed is derived. In the pulsed regime of loading, no more than half of the initial liquid volume can be dispersed to droplets less than 15 µm in diameter even if the volume-averaged dispersion of the gas-droplet system reaches extremely high values.

Optimization of culturing conditions of Porphyridium cruentum using uniform design

The red microalga Porphyridium contains many valuable compounds such as polysaccharides, polyunsaturated fatty acids, and phycoerythrin (PE). In this study, a uniform design method and regression analysis were used to investigate the effects of initial pH, light intensity, inoculation ratio, and liquid volume in flask on the optimal biomass, exopolysaccharides (EPS), and PE production of Porphyridium cruentum in a batch culture at laboratory scale. Using regression analysis, we obtained the models to clarify the effects of individual factors and their interactions on the biomass, EPS, and PE production of P. cruentum. The optimal condition for the biomass was the following: pH 5.0, light intensity 7098.0 lx, inoculation ratio 1:17.2, and liquid volume 100.0 ml; for EPS was pH 5.0, light intensity 4501.0 lx, inoculation ratio 1:20, and liquid volume 100.3 ml; while pH 8.0, light intensity 7100.0 lx, inoculation ratio 1:20, and liquid volume 100.3 ml was the best for PE production. The maximum biomass 3.27 g/l, EPS production 543.1 mg/l, and PE production 132.0 mg/l were demonstrated by confirmatory experiment to the optimum culture conditions in a reciprocal shaker. The statistical methods used in the present study are useful strategies for optimizing of culture conditions for other microalgae.

Thermal Explosion in a Flammable Gas Containing Fuel Droplets: Asymptotic Analysis

The problem of thermal explosion in a flammable gas mixture with addition of volatile fuel droplets is studied based on the asymptotic method of integral manifolds. The model for the radiative heating of droplets takes into account the semitransparency of droplets. A simplified model for droplet heat-up is used. The results of the analysis are applied to the modelling of thermal explosion in diesel engines. Two distinct dynamical situations have been considered, depending on the initial droplet concentration. These are ‘far zone’ (small initial liquid volume fraction and small droplet radii) and ‘near zone’ (large initial liquid volume fraction and large droplet radii). The conditions of the first zone are typical for the areas in the combustion chamber which are far from the fuel injectors, while the conditions of the second zone are typical for the areas in the combustion chamber which are relatively close to the fuel injectors. It has been pointed out that small droplets’ heating and evaporation time in the far zone is smaller than the chemical ignition delay of the fuel vapor/air mixture. The total ignition delay decreases with increasing initial gas temperature. In the near zone for large droplets, the process starts with the initial gas cooling and slight heating of droplets. This is followed by a relatively slow heating of gas due to the chemical reaction, and further droplet heating. The total ignition delay in the near zone is larger than in the far zone. It is expected that before thermal explosion in the near zone takes place, the droplets break up and are removed from this zone. In optically thick gas effects of thermal radiation are negligible for small droplets but are noticeable for large droplets.

Investigation of a rotating disc reactor for acetone stripping and asymmetric transfer hydrogenation: Modelling and experiments

Asymmetric transfer hydrogenation of acetophenone with isopropanol as hydrogen donor in the presence of a homogeneous catalyst was investigated in a rotating disc reactor. Initially, acetone stripping from binary mixtures acetone–isopropanol with nitrogen as inert gas was studied, since its removal is a key issue in improving reaction performance. The reactor consisted of a stainless steel disc mounted on a horizontal shaft, accommodated in a cylindrical shell. The disc was partially immersed in the liquid phase. Its rotation generated a thin liquid film on its upper part, which could be brought in contact with a gas phase used for stripping. A mathematical model was formulated to simulate the reactor and showed good agreement with experimental data for acetone stripping. It was observed that the efficiency of acetone removal from the liquid phase increased with the gas flowrate per initial liquid volume ratio. The effect of disk rotation was found to be small when the stripping gas was introduced in the liquid bulk. The reactor model agreed well with experimental data of the asymmetric transfer hydrogenation. An advantage of the rotating disk reactor is that the hydrodynamics of the phases can be decoupled and the gas flowrate can be increased without constraints in the liquid phase, unlike conventional agitated reactors that are limited by flooding. Simulations using high stripping gas flowrate per initial liquid volume, unachievable in stirred reactors, showed significant reduction of the residence time required to achieve > 99 % conversion.

Microbial biomass production from rice straw hydrolysate in airlift bioreactors

Rice straw is a by-product of rice production, and a great bioresource as raw biomass material for manufacturing value-adding protein for animal feedstock, which has been paid more and more attention. In the present work, utilizing rice straw hydrolysate as a substrate for microbial biomass production in 11.5 L external-loop airlift bioreactors was investigated. Rice straw hydrolysate obtained through acid-hydrolyzing rice straw was used for the culture of yeast Candida arborea AS1.257. The influences of gas flow rate, initial liquid volume, hole diameter of gas sparger and numbers of sieve plates on microbial biomass production were examined. The best results in the external-loop airlift bioreactor were obtained under 9.0 L initial liquid volume, 1.1 (v/v)/min gas flow rate during culture time of 0–24 h and 1.4 (v/v)/min gas flow rate of 24–48 h at 29 ± 1 °C. The addition of the sieve plates in the riser of the external-loop airlift bioreactor increased productivity. After 48 h, under optimized operation conditions, crude protein productivity with one sieve and two sieves were 13.6 mg/mL and 13.7 mg/mL, respectively, comparing 12.7 mg/mL without sieves in the airlift bioreactor and 11.7 mg/mL in the in the 10-L mechanically stirred tank bioreactor. It is feasible to operate the external-loop airlift bioreactors and possible to reduce the production cost for microbial biomass production from the rice straw hydrolysate.

Delayed thermal explosion in flammable gas containing fuel droplets: Asymptotic analysis

The problem of thermal explosion in a flammable gas mixture with addition of volatile fuel droplets is studied based on the asymptotic method of integral manifolds. The model for the radiative heating of droplets takes into account the semitransparency of droplets. A simplified model for droplet heat-up is used. The results of the analysis are applied to the modelling of thermal explosion in diesel engines. Two distinct dynamical situations have been considered, depending on the initial droplet concentration. These are ‘far zone’ (small initial liquid volume fraction and small droplet radii) and ‘near zone’ (large initial liquid volume fraction and large droplet radii). The conditions of the first zone are typical for the areas in the combustion chamber which are far from the fuel injectors, while the conditions of the second zone are typical for the areas in the combustion chamber which are relatively close to the fuel injectors. It has been pointed out that small droplets’ heating and evaporation time in the far zone is smaller than the chemical ignition delay of the fuel vapor/air mixture. The total ignition delay decreases with increasing initial gas temperature. In the near zone for large droplets, the process starts with the initial gas cooling and slight heating of droplets. This is followed by a relatively slow heating of gas due to the chemical reaction, and further droplet heating. The total ignition delay in the near zone is larger than in the far zone. It is expected that before thermal explosion in the near zone takes place, the droplets break up and are removed from this zone. In optically thick gas effects of thermal radiation are negligible for small droplets but are noticeable for large droplets.

Internal Entropy Generation Limits for Direct Sensible Thermal Storage

This paper presents results for the entropy generated internally during the charging and discharging processes of a direct, sensible thermal energy store. The two processes correspond to the inflow of either a low or high temperature liquid stream into an enclosure initially filled with a uniformly high or low temperature liquid, respectively. The level of internal entropy generation due to thermal mixing between the inflow and the initial liquid volume corresponds to losses in the usable fraction of the stored volume and therefore decreased efficiency. Empirically, the observed behavior of direct sensible storage devices spans the range of nearly mixed to highly stratified. In the present work, analytical models for the fully-mixed and ideally-stratified limits are used to bound these behaviors and to analytically determine the corresponding entropy generation levels. The ratio of total entropy generation for the ideally-stratified limit relative to that of the fully-mixed limit is shown to vary as 8/πPe. The limiting behaviors therefore define a continuum of entropy generation levels separated by up to several orders of magnitude for typical Peclet numbers. A published numerical model which accounts for aspects of the observed thermal mixing is then examined in relation to these limits. The model predicts entropy generation levels midway between the limiting behaviors which suggests significant potential for improvements in the efficiency of direct sensible storage devices.

EVALUATION OF FOAM FRACTIONATION COLUMN SCALE-UP FOR RECOVERING BOVINE SERUM ALBUMIN

Foam fractionation is an adsorptive-bubble separation method that, according to researchers, is a feasibletechnique for the separation and/or concentration of proteins. The foam fractionation of bovine serum albumin (BSA) inlaboratory -scale foam fractionation columns (750 and 1250 mL) and the relationship between the two laboratory-scalecolumns and a pilot-scale column (5000 mL) were investigated. Recovery, enrichment, and performance factor values wereexperimentally determined with three different column volumes with varying pore sizes, gas superficial velocities, and, in thecase of the 750 mL column, foam column height. As the pore size decreased, the amount of protein recovered from the diluteprotein solution increased and the enrichment decreased. As the flow rate of the gas increased, the effect of the pore sizedecreased. For the three column volumes, the optimal column conditions were achieved with the largest pore size (145-174 .m) and an intermediate superficial gas velocity (7 mm/s). Increasing the foam column height increased the enrichmentwithout sacrificing the recovery of the target protein. In the case of the largest pore size, the linear relationships between therecovery and the ratio of gas volume to initial liquid volume are parallel, such that the recovery in a pilot-scale column(5000 mL) can be predicted with the recovery found with a laboratory-scale column (750 or 1250 mL).

Pressure-driven capillary snap-off of gas bubbles at low wetting-liquid content

Abstract Snap-off is an important mechanism for generating discontinuous gas bubbles in porous media. Here, we use a hydrodynamic, corner-flow theory to re-examine the breakup of gas threads in constricted pores. Our primary focus is on the initial liquid volume within the corners of a pore and on the possibility of a minimum liquid content below which snap-off is inhibited. It is found that smoothly constricted pores with relatively small throats connected to large bodies exhibit excellent ability to snap-off regardless of their initial liquid content. Where such pores are present in porous media, it is predicted that strong foam is generated. Additional factors contributing to snap-off include elevated pressure gradients in the liquid phase and lamella or lens movement that establishes gradients in the axial profile of interfacial curvature. Our new results re-support successive snap-off as a viable mechanism of steady foam generation in homogeneous porous media at low overall aqueous-phase liquid content and at high liquid-phase pressure gradient.

Effect of Sampling Time on the Collection Efficiency of All-Glass Impingers

The changes in the physical collection efficiencies of all-glass impingers were studied experimentally with an aerodynamic particle sizer by dynamically measuring the particle concentrations upstream and downstream of AGI-4 and AGI-30 impingers. Monodisperse PSL particles of aerodynamic sizes ranging from 0.3 to 2.0 μm were used in the tests. The inner diameter of the impingement nozzle was found to be the most critical dimension affecting the collection efficiency. Significant variations were found in the performance of individual impingers due to the variations in the critical dimensions of the impingers tested. About 1% of the initial amount of impinger liquid is evaporated per minute of normal operation. On depletion to a critical minimum volume, the collection efficiency decreases drastically due to insufficient impingement into the liquid and particle bounce from the bottom surface. Particles already collected may be entrained by the air bubbles passing through the liquid and be reaerosolized, thus decreasing the overall collection efficiency. The number of reaerosolized particles increases with sampling time, but is less than 10% within the first hour of sampling with either the AGI-4 or the AGI-30. A graph has been developed for selecting the maximum sampling time for a given initial liquid volume so that the collection efficiency is approximately constant throughout the entire sampling period. The graph also indicates the limits where significant particle bounce, reaerosolization, or liquid splashing occur. The AGI-4 was found to be more efficient in collecting submicrometer particles and to be less particle-size dependent than the AGI-30.

Droplet combustion near a cold surface

The combustion of a liquid droplet adjacent to a cold surface was studied experimentally. To isolate the effect of the proximity of the droplet to the surface, the ambient pressure (0.101 MPa), liquid composition ( n -heptane), initial liquid volume (7 x 10 -4 ml), surface material (quartz) and ambient temperature (20 ± 2°C) were held constant. A range of distances L from the surface were studied (1 mm < L < ∞). Both horizontal and vertical surface orientations were examined. A more limited set of experiments were carried out in a low gravity (i. e. low buoyancy) environment to provide a basis of comparison with relevant theoretical analyses. The flame shape, soot formation, fuel condensation, and droplet burning rate were all found to be strongly affected by the proximity of the droplet to the surface. For sufficiently large L the flame was observed to be closed around the droplet throughout burning. As L decreased, the flame was truncated. The droplet burning rate decreased as the droplet was brought progressively closer to the surface (in qualitative agreement with a relevant closed form potential flow solution to the analogous problem of a droplet burning adjacent to an adiabatic surface) and the burning rate of a droplet adjacent to a vertical surface was larger than for a horizontal surface. Surface orientation effects were observed to be absent for burning at low gravity. The extent of sooting as revealed by the flame colour was decreased, and fuel vapours condensed in a lens-like shape on the surface, as L was sufficiently reduced.

紙の表面マイクロトポグラフィー ＩＩＩ 紙の表面粗さと吸液特性の関係

Liquid transfer and dynamic penetration as well as their relationships to roughness of papers, such as softwood and hardwood bleached sulphate pulp sheets and commercial india and coated papers, were investigated.As smoothness of paper surface increased, the initial liquid transfer and absorption volume decreased. The amount of water transfered at the contact time 0, which could be obtained by extrapolation from the relationship between liquid transfer and contact time, might be interpreted as the roughness index Kr'. This became smaller when the void volume on the paper surface decreased. Moreover, the thickness of water layer and its volume ratio to that of void on the paper surface at the initial stage were calculated as 11.1 μm and 46% for the softwood bleached sulphate sheet, 9.6μm and 54% for the hardwood sheet, 8.8 μm and 41% for the india paper and 1.8μm and 16% for the coated paper, respectively.

Sedimentation of supsensions: implications of theories of hindered settling

Expressions are derived for the parameters A in Steinour's theory and n Richardson and Zaki's expression dealing with the hindered settling of powdered materials. It is shown that n is simply related to ϵ 1, the initial liquid volume fraction of a uniformly mixed suspension for which [ Q(1 — ϵ)] was maximum value, Q being the linear settling rate of the suspension/supernatant interface and ϵ the initial liquid volume fraction of the suspension. For systems obeying the Richardson-Zaki expression, the settling rate at ϵ 1 approaches the limit V s exp −1, where V s is the estimated Stokes' law limiting velocity for the system, when ϵ 1 approaches unity ( i.e. infinite dilution). Highly hindered systems have large values for n, and ϵ 1 values approaching unity; for such systems Q ϵ 1 ⋍ V s exp −1. It is suggested that such behaviour implies the existence of relatively long-range forces within suspensions, hindering settling, and that particle-liquid (including particle-liquid-particle) forces are of importance in addition to particle-particle interactions. Evidence is presented that hindrance to settling is directly proportional to the polarity of the solid/liquid system and that the density of charge on the superficial particle surface is the dominant factor in determining hindrance. Maximum reduction of surface polarity without causing flocculation is suggested as the most efficient condition for separation by settling under gravity and pumping off supernatant liquor. n and ϵ 1 can be considered as useful indices of hindrance to sedimentation. ϵ 1 has particular significance as the initial liquid volume fraction at which solids flux has maximum value (for any suspension which obeys the Richardson-Zaki equation).