Drop pressure experiment

Fig. 5.19 Principle of a drop pressure experiment according to MacLeod Radke (1993) C - capillary, M - motor driven syringe for liquid 1, LI - liquid 1, L2 - reservoir of liquid 1, PC - computer, V - video camera with objective, VR - video recorder, PT - pressure transducer, SAC - signal amplifier and converter...

The drop pressure experiment developed by Nagarajan Wasan (1993), and Horozov et al. 

An example of the results obtained from drop pressure experiments is given in Figure 12.14, where the dynamic interfacial tension is displayed as a function of time. For the lowest concentration of 2 x 10 mol/cm, the time interval from 0.1 to 10 s is far from sufficient to obtain the equilibrium interfacial tension, while at the highest concentration of 4 x 10 mol/cm the equilibrium is almost reached after a period of 10 s. Plots of y against ( /y/i) allow a good extrapolation of equilibrium tension values. As the pressure sensor can be read with... 

Aranaz98 reports that the explosion of tetryl produces a temperature of 3339°. Tetryl is slightly more sensitive than picric acid, and considerably more sensitive than TNT, in the drop test. Experimenting with a 5-kilogram weight, Koehler found that a drop of 150 cm. caused the detonation of tetryl 10 times out of 10 trials, a drop of 100 cm. 9 times out of 10, of 50 cm. 5 times out of 10, and of 40 cm. 3 times out of 10. Martin99 has determined the minimum charges of various primary explosives necessary for the detonation of TNT and tetryl. The explosives were loaded into detonator capsules, and the initiators were compressed upon them at a pressure of 1100 kilos per square centimeter. 

In both BSR modules, the Sherwood number lies between the two Chilton-Colbum predictions, as expected. The most important conclusion to be drawn from these graphs, is that the Sherwood number for turbulent flow in a BSR can be predicted with an accuracy of ca. 30% (which is usually acceptable) on the basis of one single pressure drop experiment in the turbulent-flow regime. From this pressure experiment the empirical roughness function can be fitted, with which the friction factor can be adequately predicted as a function of Re, as discussed in the previous section from these an upper estimate of Sh... 

Drop impact resistance of fluid-filled plastic containers is of considerable concern to containers manufacturers as well as distribution industries using the containers for transportation of various liquids. This is due to potential failure of the containers following the drop impact and subsequent spillage of the transported liquid, and consequent safety and economical Issues. In this work, a series of drop impact experiments is conducted on water filled bottles made of blow moulded high-density polyethylene (HDPE). During experiments, pressure and strain histories are recorded at various positions. The experiments are then simulated numerically. 

This paper presents the combined experimental/numerical investigation of the behaviour of fluid-filled plastic containers subjected to drop impact. Drop Impact experiments were conducted on original and modified bottles. During the test, strain and pressure histories were recorded at various positions. Tests were simulated numerically using the two-system FSI model. Both solid and fluid domains remain fixed during the calculations, i.e. a small-strain analysis was performed for the solid while an Eulerian fi-ame of reference was used for the fluid. This procedure was found to be simple, stable and efficient. Numerical results agreed well with experimental data, demonstrating the capability of the code to cope with this complex fluid-structure interaction problem. 

EMPIRICAL EQUATIONS FOR CAKE RESISTANCE. By conducting constant-pressure experiments at various pressure drops, the variation of a with Ap may be found. If a is independent of Ap, the sludge is incompressible. Ordinarily a... 

The kinetics of the adsorption process taking place at the surface of a growing drop or bubble is important for the interpretation of data from drop volume or maximum bubble pressure experiments. The same problem has to be solved in any other experiment based on growing drops or bubbles, such as bubble and drop pressure measurements with continuous, harmonic or transient area changes (for example Passerone et al. 1991, Liggieri et al. 1991, Horozov et al. 1993, Miller at al. 1993, MacLeod Radke 1993, Ravera et al. 1993, Nagarajan Wasan 1993). 

The diagram in Fig. 5.26 shows schematically the ratio between the experimental time t, which is the life time of a drop or bubble in the respective experiment, and the effective adsorption time Tg. It becomes clear that each experimental method works under specific conditions and, therefore, different relations between a specific experimental time and the effective adsorption time or surface age exist. While the effective age igina maximum bubble pressure experiment... 

Future developments will also focus on the combination of different techniques, such as drop pressure and drop shape methods. A more efficient approach would be to combine macroscopic with microscopic or molecular methods, for example drop shape or pressure experiments with ellipsometric or spectroscopic techniques. Another useful possibility involves linking, for example, the inclinded plate or overflowing cylinder technique with scattering experiments, which would allow studies of structure formation under dynamic conditions and at freshly formed surfaces (Howe et al. 1993). 

There is one point important to note here, the experimental data plotted as y( - 1) must cross the ordinate at a value identical to the surface tension of the surfactant-free system, i.e. the surface tension of water for a water/air interface. This is often not the case, in particular for drop volume or maximum bubble pressure experiments where due to the peculiarities of the measurement an initial surfactant load of the interface exists. It has been demonstrated in the book by Joos [16] that even in these cases, assumed it is the initial period of the adsorption time, the slope of the plot y( /t) yields the diffusion relaxation time defined by Eq. (4.26) and hence information about the diffusion coefficient. For small deviation from equilibrium we have the relationship... 

Experimental set-ups as well as the corresponding theoretical models for these and other capillary pressure methods have been described in detail in a chapter by Liggieri and Ravera in the book on drops and bubble [197], These authors also discuss very detailed the problems coimected with the various experimental procedures used in the investigations with drop pressure methods. Most of all the theoretical basis of this group of experiments is well described and offers a good chance to quantitatively understand surfactant systems. 

In drop/bubble experiments, either working with transient (aperiodic) procedure or with harmonic (periodic) procedure, there never is a continuous function g(t) to be analysed. There is instead a list of measurements of g(tj) for a discrete set of N time values ti, where g(t) represents the time-evolution of the inherent interfacial physical and geometrical properties (surface tension, differential pressure, interfacial area, et cetera). 

It was apparent that the factor characterising the friction between gas flow and wall needed to increase with increasing flow rate of solids, to yield the increasing bend pressure drop observed. Experiment suggested a linear relationship against suspension density, with an intercept when such a relationship was imposed on the value and optimisation of the slope and intercept values of the relationship was undertaken, the relationship yielding least discrepancy between model and data was as shown overleaf -... 

Obviously the predictions of the models differ considerably. While the models of Stairmand and Shepherd and Lapple agree reasonably well, the Casal/Mar-tinez and Barth models differ by almost a factor of two. In the following chapter we shall put the models for pressure drop to a test we shall compare their predictions of the effect of cyclone length on pressure drop with experiment. 

If the experiment was now reversed, starling from A and increasing the pressure, the first drop of ethane liquid would appear at point C, the dew point of the gas. Remember that throughoufthis process, isothermal conditions are maintained. 

The film pressure is defined as the difference between the surface tension of the pure fluid and that of the film-covered surface. While any method of surface tension measurement can be used, most of the methods of capillarity are, for one reason or another, ill-suited for work with film-covered surfaces with the principal exceptions of the Wilhelmy slide method (Section II-6) and the pendant drop experiment (Section II-7). Both approaches work very well with fluid films and are capable of measuring low values of pressure with similar precision of 0.01 dyn/cm. In addition, the film balance, considerably updated since Langmuir s design (see Section III-7) is a popular approach to measurement of V. 

Neumann has adapted the pendant drop experiment (see Section II-7) to measure the surface pressure of insoluble monolayers [70]. By varying the droplet volume with a motor-driven syringe, they measure the surface pressure as a function of area in both expansion and compression. In tests with octadecanol monolayers, they found excellent agreement between axisymmetric drop shape analysis and a conventional film balance. Unlike the Wilhelmy plate and film balance, the pendant drop experiment can be readily adapted to studies in a pressure cell [70]. In studies of the rate dependence of the molecular area at collapse, Neumann and co-workers found more consistent and reproducible results with the actual area at collapse rather than that determined by conventional extrapolation to zero surface pressure [71]. The collapse pressure and shape of the pressure-area isotherm change with the compression rate [72]. 

In order to vaUdate this concept, an experiment was performed using an ice-water slurry and it was found that a 25% ice slurry had a two-to-four-times higher thermal capacity than chilled water (44). As the concentration of ice particles in the ice-slurry mixture increased up to 30%, no significant change of pressure drop was reported compared to pure water. 

OTSGs also experience deposition of material on the flow areas in the tube support plates which causes an increase in pressure drop and eventual reductions in plant power production. 

---