Fields of a gas

If we consider two spheres in the vibratory field of a gas stream it may be shown that the forces acting on the spheres (in the cz-plane), provided the motion is streamline, are (Konig, 1891),... 

In this way, the relative dielectric response to static electric fields of a gas of polarizable molecules that also bear a permanent dipole moment is... 

As noted earlier, most electron diffraction studies are perfonned in a mode of operation of a transmission electron microscope. The electrons are emitted themiionically from a hot cathode and accelerated by the electric field of a conventional electron gun. Because of the very strong interactions between electrons and matter, significant diffracted intensities can also be observed from the molecules of a gas. Again, the source of electrons is a conventional electron gun. 

Maxwell considered the motion of a gas in the neighborhood of a plane solid wall, in che presence of a temperature gradient. In particular, when Che velocity field is one dimensional and everywhere parallel to the wall, and the temperature gradient is parallel to the velocity field, he found that... 

The high potential and small radius of curvature at the end of the capillary tube create a strong electric field that causes the emerging liquid to leave the end of the capillary as a mist of fine droplets mixed with vapor. This process is nebulization and occurs at atmospheric pressure. Nebulization can be assisted by use of a gas flow concentric with and past the end of the capillary tube. 

The electrical conductivity O of a gas is defined as the ratio of the current to the field, ie, from the most general form of Ohm s law. Neglecting ion mobihty, this becomes equation 16, which can be written in terms of the current density components ... 

Gonzalez, Fr., Boyce, Me. P., Solutions to Field Problems of a Gas Turbine-Axial Flow Chemical Process Compressor Train Based on Computer Simulation of the Process, Proceedings of the 28th Turbomachinery Symposium, Texas A M University, p. 77, 1999. 

The combustion-flow interactions should be central in the computation of combustion-generated flow fields. This interaction is fundamentally multidimensional, and can only be computed by the most sophisticated numerical methods. A simpler approach is only possible if the concept of a gas explosion is drastically simplified. The consequence is that the fundamental mechanism of blast generation, the combustion-flow interaction, cannot be modeled with the simplified approach. In this case flame propagation must be formalized as a heat-addition zone that propagates at some prescribed speed. 

Morecambe Bay The Morecambe Bay field is a recently developed gas field in the Irish Sea connected to the NTS by means of a gas pipeline to Barrow terminal. While it is possible to operate this field throughout the year, it is currently being drawn on only in the winter months as a form of peak-shaving. 

The principal applications of mass transfer are in the fields of distillation, gas absorption and the other separation processes involving mass transfer which are discussed in Volume 2, In particular, mass transfer coefficients and heights of transfer units in distillation, and in gas absorption are discussed in Volume 2,. In this section an account is given of some of the experimental studies of mass transfer in equipment of simple geometry, in order to provide a historical perspective. 

In the authors experience, the amount of carbon dioxide in 10 microliters of blood can readily be determined by adding the blood to an acid, through which bubbles an inert gas. The CO2 is then brought into the field of a long cuvette, of approximately 20" in length, and the carbon dioxide measured at the near infrared with a filter instrument. Instrumentation can be designed readily for measurement of the carbon dioxide content of as little as 1 l of plasma with this principle at the rate of approximately 40-60 per hour. 

Membranes act as a semipermeable barrier between two phases to create a separation by controlling the rate of movement of species across the membrane. The separation can involve two gas (vapor) phases, two liquid phases or a vapor and a liquid phase. The feed mixture is separated into a retentate, which is the part of the feed that does not pass through the membrane, and a permeate, which is that part of the feed that passes through the membrane. The driving force for separation using a membrane is partial pressure in the case of a gas or vapor and concentration in the case of a liquid. Differences in partial pressure and concentration across the membrane are usually created by the imposition of a pressure differential across the membrane. However, driving force for liquid separations can be also created by the use of a solvent on the permeate side of the membrane to create a concentration difference, or an electrical field when the solute is ionic. 

Ionization in the condensed phase presents a challenge due to the lack of a precise operational definition. Only in very few cases, such as the liquefied rare gases (LRG), where saturation ionization current can be obtained at relatively low fields, can a gas-phase definition be applied and a W value obtained (Takahashi et al., 1974 Thomas and Imel, 1987 Aprile et al., 1993). 

In field ion microscopy, ions of a gas such as hydrogen or one of the rare gases image the tip. The principle is shown in Fig. 7.10 for helium. A high positive potential... 

Previous studies of Vapor Cloud Explosions (VCE) have used a correlation between the mass of a gas in the cloud and equivalent mass of TNT to predict explosion overpressures. This was always thought to give conservative results, but recent research evidence indicates that this approach is not accurate to natural gas and air mixtures. The TNT models do not correlate well in the areas near to the point of ignition, and generally over estimate the level of overpressures in the near field. Experiments on methane explosions in "unconfined" areas have indicated a maximum overpressure of 0.2 bar (2.9 psio). This overpressure then decays with distance Therefore newer computer models have been generated to better simulate the effects... 

Figure 3.1. Sketch of Batchelor-scale scalar field in a gas-phase flow. 

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