Dynamic flow experiments

Also, other dependent variables associated with CO2-foam mobility measurements, such as surfactant concentrations and C02 foam fractions have been investigated as well. The surfactants incorporated in this experiment were carefully chosen from the information obtained during the surfactant screening test which was developed in the laboratory. In addition to the mobility measurements, the dynamic adsorption experiment was performed with Baker dolomite. The amount of surfactant adsorbed per gram of rock and the chromatographic time delay factor were studied as a function of surfactant concentration at different flow rates. 

Results and Discussion on Dynamic Adsorption Measurements. Baker dolomite was used to study the dynamic adsorption experiment. The computed porosity of the rock was 24%. One concentration below the CMC of AEGS, one at CMC, and two concentrations above CMC were chosen to measure the adsorption of this surfactant with Baker dolomite. The mass of surfactant adsorbed per gram of rock is plotted as a function of flow rate in a semi-log plot in Figure 9. 

The slopes of the peaks in the dynamic adsorption experiment is influenced by dispersion. The 1% acidified brine and the surfactant (dissolved in that brine) are miscible. Use of a core sample that is much longer than its diameter is intended to minimize the relative length of the transition zone produced by dispersion because excessive dispersion would make it more difficult to measure peak parameters accurately. Also, the underlying assumption of a simple theory is that adsorption occurs instantly on contact with the rock. The fraction that is classified as "permanent" in the above calculation depends on the flow rate of the experiment. It is the fraction that is not desorbed in the time available. The rest of the adsorption occurs reversibly and equilibrium is effectively maintained with the surfactant in the solution which is in contact with the pore walls. The inlet flow rate is the same as the outlet rate, since the brine and the surfactant are incompressible. Therefore, it can be clearly seen that the dynamic adsorption depends on the concentration, the flow rate, and the rock. The two parameters... 

CDs can form complexes with stoichiometries different from 1 1. Stopped-flow experiments were employed to study the binding dynamics of a 2 2 complex between pyrene and y-CD.196 Both, 1 1 and 2 2 complexes are formed and the 2 2 complex exhibits excimer-like emission. The association rate constant for the 2 2 complex was found to be 6 x 107M-1 s-1, while the dissociation rate constant was 73 s-1. These values correspond to a decrease of up to 5 orders of magnitude when compared to the dynamics for the 1 1 complex. 

Stopped-flow experiments, 171-172 cyclodextrins (CD), binding dynamics of guests binding to, 205, 207, 208 DNA, binding dynamics of guests binding to, 187, 189-191, 194, 195-196... 

Fig. 7 presents partial results of dynamic regime experiments for chromate adsorption and desorption by ODA-clinoptilolite. As shown by breakthrough curves, ODA-clinoptilolite column quantitatively removes chromate species from simulated waste water , apparently more efficiently by lower flow rate. Consequently to similar configuration of chromate and sulfate molecules, such loaded column was more efficient to regenerate with Na2S04 than NaCl solution, as elution curves at the Fig. 7 illustrate. 

An important requirement of kinetic studies for automotive aftertreatment devices is the capability of performing dynamic reactive experiments. Steady-state tests provide useful information for identification of reaction pathway and stoichiometry, but cannot capture the real operating behavior of catalytic converters for vehicles, which is transient in nature. Indeed, this is so not only because of the continuously changing conditions (temperature, composition, flow rate) of the engine exhausts as extensively addressed in the following sections, the principles of NSRC and SCR applications largely rely on the storage/reaction/release dynamics of NOx and of NH3, respectively. 

Understanding the shape of the chronoamperogram requires consideration of concentration-distance profiles for a potential-step excitation in conjunction with Faraday s law. Faraday s law is so fundamental to dynamic electrochemical experiments that it cannot be emphasized too much. It is important to keep in mind that the charge Q passed across the interface is related to the amount of material that has been converted, and the current i is related to the instantaneous rate at which this conversion occurs. Current is physically defined as the rate of charge flow therefore,... 

The computational approach couples the two-phase LB model for the liquid water transport and the DNS model for the species and charge transport for the CL.25-27,68 The two-phase simulation using the LB model is designed based on the ex-situ, steady-state flow experiment for porous media, detailed earlier in the section 4.3, in order to obtain the liquid water distributions within the CL microstructure for different saturation levels resulting from the dynamic interactions between the two phases and the underlying pore morphology. The details of the simulation setup are provided in our work.27,61 62 Once steady state is achieved, 3-D liquid water distributions can be obtained within the CL, as shown in Fig. 13. From the liquid water distributions within the CL structure, the information about the catalytic site coverage effect can be extracted directly. 

Applications of optical methods to study dilute colloidal dispersions subject to flow were pioneered by Mason and coworkers. These authors used simple turbidity measurements to follow the orientation dynamics of ellipsoidal particles during transient shear flow experiments [175,176], In addition, the superposition of shear and electric fields were studied. The goal of this work was to verify the predictions of theories predicting the orientation distributions of prolate and oblate particles, such as that discussed in section 7.2.I.2. This simple technique clearly demonstrated the phenomena of particle rotations within Jeffery orbits, as well as the effects of Brownian motion and particle size distributions. The method employed a parallel plate flow cell with the light sent down the velocity gradient axis. 

P) atoms with 1-alkynes and from the reactions of CH2 with 0(3P), 02 and C02. These reactions can not be readily studied with other techniques such as chemiluminescence (due to low product concentrations as well as the difficulty in producing radical species in flow experiments). With the aid of simple statistical models, the dynamics and branching ratios of these reactions can be reasonably interpreted and crudely estimated. More detailed discussion of the application of this technique to many other examples including energy transfer reactions has recently been reviewed elsewhere... 

The basic idea of the dynamic pressurization (DP) experiment is similar to the dynamic gas expansion (DGE) method. Both use a sudden pressure change around a gel specimen to initiate gas flow into or out of the sample, thus avoiding the delicate leakage problems typically encountered in static gas flow setups. While DGE monitors the gas pressure outside the gel as a function of time and deduces the permeability from its equilibration behavior (in principle a dynamic pycnometry experiment). DP utilizes the dynamics of the elastic deformation of the gel to deduce both elastic modulus and permeability. The deformation, or strain, is a consequence of the pressure difference between the interior and the exterior of the specimen. For example, after a sudden increase in pressure, the gas in the gel pores is initially only slightly compressed along with the elastic compression of the gel. After a characteristic time, the pressure equilibrates and the gel ideally springs back to its original dimensions. 

The water-sorption experiments were carried out in a dynamic flow vapor sorption apparatus (Model SGA100, VTI Corporation, Hialeah, FL). Samples of the two polymorphs were placed in the instrument s sample chamber and their moisture uptake as a function of relative humidity (RH) was measured. Water-sorption isotherms for both polymorphs were carried out imder the temperature conditions of 20, 25, 35, and 45°C. The amoimt of sample used for an analysis depends on the sample s tendency to pick up water. If the sample is highly hygroscopic, about 2-5 mg is sufficient for the test, but if the sample is nonhygroscopic, a larger mass is needed, about 25 mg or more. For this study, water-sorption isotherms for both polymorphs were carried out using the flow system and a sample size of about 50 mg. 

To extract TMB from TMB-methanol mixtures it is necessary to find a solvent that is relatively immiscible in methanol yet is miscible with TMB at the same conditions. TMB is very soluble in benzene, hexane, heptane, nonane, and carbon tetrachloride indicating that it exhibits very lipophilic characteristics (Plank and Christopher, 1976 Niswonger, Plank, and Laukhuaf, 1985 Schmidt, Plank, and Laukhuf, 1985 Munster et al., 1984). Hence, TMB should be soluble in the more common supercritical fluid solvents such as ethane and carbon dioxide. Methanol is moderately miscible with xenon, ethane, ethylene, and carbon dioxide since a single phase is obtained at pressures of less than —200 bar at temperatures between the respective critical temperatures of the binary components (Brunner, 1985). To obtain quickly an estimate of the distribution coefficient for TMB in carbon dioxide, ethane, and ethylene, rapid screening experiments were performed with a dynamic flow apparatus at temperatures ranging from 0 to 55°C at a number of pressures. From this preliminary study it was found that carbon dioxide does not... 

In engineering computations, the turbulent transport of properties is usually treated in a statistical manner, where computations are concerned with the mean velocities, temperatures, and/or concentrations. This statistical approach, however, masks many of the actual physical processes in the dynamic flow field, which must be recovered by the modeling at some level of the turbulence statistics. This modeling was originally guided by the results from experiments, but currently this guidance can rely on simulations as well. 

Tinkler 19) and Sinai 20) used frequency response analysis to study homogeneous reactions in the liquid phase accompanied by flow through packed beds of solids. Temperature and concentration were varied. Dynamic response experiments in homogeneous reactors are analyzed by Tinkler and Lamb 21). 

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