Entrapped gases

Permeability Bulk sohd permeability is important in the iron and steel industiy where gas-solid reactions occur in the sinter plant and blast furnace. It also strongly influences compac tion processes where entrapped gas can impede compaction, and solids-handling equipment where restricted gas flow can impede product flowabihty. The permeabihty of a granular bed is inferred from measured pressure drop under controlled gas-flow conditions. 

Adiabatic Compression of Entrapped Gas or Vapor as a Cause of Initiation of Explosives. See Vol 1, p A103-L... 

C.G. Wade, USP 3715247(1973) CA 78, 126471(1973) [Water-in-oil emulsion expl containing entrapped gas. An example is AN 31-7, NaN03 10, Ediylenediamine Dinitrate 10, NH4CI04 10, magnesium nitrate hexahydrate 12.3 and water 20 (heated until all dissolved), blended with a mixture of Indra 2119 wax 2 and sorbitan monooleate 10 parts, followed by addition of Corcel hollow glass agglomerates to make 100 parts]... 

Adiabatic Compression of Entrapped Gas or Vapor as a Cause of Initiation of Explosives. It has been shown by some Brit investigators that one of the important causes of initiation of sensitive expls by mech actionfsuch as impact) is the adia-... 

Adiabatic compression of entrapped gas or vapor as a cause of initiation of expls 1 A103... 

The contact resistance should increase with a decrease in the ambient gas pressure when the pressure is decreased below the value where the mean free path of the molecules is large compared with a characteristic dimension of the void space, since the effective thermal conductance of the entrapped gas will be decreased for this condition. 

In nucleate boiling, bubbles are created by the expansion of entrapped gas or vapor at small cavities in the surface. The bubbles grow to a certain size, depending on the surface tension at the liquid-vapor interface and the temperature and pressure. Depending on the temperature excess, the bubbles may collapse on the surface, may expand and detach from the surface to be dissipated in the body of the liquid, or at sufficiently high temperatures may rise... 

The formation of gas bubbles in a porous medium affects, e.g., the performance of anaerobic granular sludge particles containing entrapped gas (waste-water treatment), or the performance of electrochemical reactors where a gas (hydrogen, oxygen, chlorine) evolves inside a porous electrode. A related problem is that of bubble nucleation on structure surfaces, which can be as varied as specially designed surfaces for enhanced nucleate boiling heat transfer, or the... 

The mechanism of bubble formation by nucleation requires supersaturation of the dissolved gas [11-13] and a nucleus radius greater than the critical [7], The main sources of heterogeneous nucleation are usually surface irregularities capable of containing entrapped gas, e.g. pits and scratches. The bubbles typically develop over the electrode surface, grow in size until they reach a break-off diameter and subsequently detach into the electrolyte. After detachment, some residual gas remains at the nucleation site and another bubble will form at the same place [2,13,14], In most two-phase flow simulations [15-19], it is assumed that bubbles detach with a constant diameter, although from experiments [20,21] it is know that electrochemically formed bubbles show a size distribution. 

The ultrasound reflectivity of entrapped gas in echogenic liposomes allows real time image-guided drug and gene delivery. 

This protocol can be adapted for many other types of cell. In the gene transfection for adherent cells, the transfection efficiency in the condition of suspension was higher than that in the condition of adhesion on the culture plate. Although this result is unclear, it is thought that the distance between BLs and cells is important. Because BLs entrapping gas is easy to flow and result in getting away from the adherent cells on the plate. 

Expulsion of entrapped gas (air) from granulated or (particularly) powder feeds is very important because it reduces lamination and capping of the tablets. As repeatedly mentioned (also, for example. Section 10.2 and [B.48, B.97]), if gas is entrapped in compacts where it becomes compressed in the residual pore spaces and/or elastic deformation is still present when the compaction pressure is released, products from pressure agglomeration methods are partially or totally destroyed during ejec-... 

Other effects are related to depth. Protective garments which rely on entrapped gas for their insulating power lose much of their effectiveness at depth because the material compresses. For example, a 1/4-inch nylon-lined wet suit compresses to about 50% of its original thickness when subjected to a pressure of 4 atm (19). In addition to reducing the insulating power of the suit, compression also reduces the buoyancy. This can cause a serious problem for the diver when a thick foam suit is used to give thermal insulation. 

Unfractionated excess air. The most straightforward explanation of the phenomenon of a gas excess above atmospheric equilibrium in ground waters is complete dissolution of small air bubbles trapped in soil pores (Fig. 5a, Heaton and Vogel 1979, 1981 Rudolph et al. 1984). This traditional—but experimentally never directly verified— concept implies that the excess has the same composition as the entrapped gas, which is assumed to be atmospheric air, hence the name excess air . We refer to this concept as the unfractionated air (ElA) model. Because the composition of air is given by the volume fractions Zi, the ETA-model needs only one parameter to describe the excess air component, namely the amount of trapped and completely dissolved air per mass of water (Ad). The excess air term in Equation (5) is written as ... 

The model parameters Ag and F in the CE-model have a clear physical interpretation (Aeschbach-Hertig et al. 2000, 2001). Ag given in cm STP g approximately equals the initial volume ratio between entrapped air and water, whereas F describes the reduction of the gas volume by partial dissolution and compression. Correspondingly, F can be expressed as the ratio of two parameters v and q, where v is the ratio of the entrapped gas volumes in the final (Vg) and initial state (Vg ), and q is the ratio of the dry gas pressure in the trapped gas to that in the free atmosphere (P) ... 

Complete dissolution of entrapped air was only achieved if the sand column was continuously flushed with air-saturated water at relatively high flow rates. Numerical modeling of the kinetics of gas exchange between entrapped gas and water enabled an understanding of the mechanisms that lead to different type of excess air fractionations depending on the experimental setup. Both the numerical model and the data showed that after a water table increase a new equilibrium between water and entrapped air was quickly achieved, although in the first phase complete dissolution of the smallest bubbles is possible. 

Foaming Forms stable films to entrap gas Whipped toppings, chiffon desserts, angel food cakes 1, W, H... 

In externally imposed inhomogeneous magnetic fields (TO 0) the rotational forces may generate sufficiently strong vortices in the solid/liquid interface sublayers to destroy the layer structure on account of large MHD-stresses appearing on the capillary walls (also on the surface of microscopic particles and entrapped gas bubbles in the flow, if impurities are present). The critical flow velocity for structure destruction is [125]... 

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