Gas zones

If the gas volume is not isothermal and is zoned, an additional magnitude, the gas-to-gas total-exchange area QGj, arises (see Hottel and Sarofim. Radiative Tran.sfer, McGraw-Hill, New York, 1967, chap. 11). Space does not permit derivations of special cases only the single-gas-zone system is treated here. 

Sin e-Gas-Zone/Two-Surface-Zone Systems An enclosure consisting of but one isothermal gas zone and two gray surface zones can, properly specified, model so many industrially important radiation problems as to merit detailed presentation. One can evaluate the total radiation flux between any two of the three zones, including multiple reflec tion at all surfaces. 

The simplest application of this simple gray-plus-clear model of gas radiation is the case of a single gas zone surrounded by a single surface zone, Eq. (5-163) for a gray gas. The gray-plus-clear model gives... 

Intermittent (I) - In this flow pattern the liquid inventory in the pipe is non-uniformly distributed axially. Plugs or slugs of liquid that fill the pipe are separated by gas zones that contain a stratified liquid layer flowing along the bottom of the... 

If an oil or gas zone is present above this water sand, R should be computed the same way and calculated. 

After detachment of the flame from the wall and reduction of its width, three zones develop in the vessel parallel to each other a flame and burned gas zone and two zones (adjacent to the sidewalls), where no flame is present and where the gas temperatures are lower than behind the flame. All this happens in a field of very high centrifugal acceleration, which induces a free convection movement of the flame and the product zone behind it toward the... 

The film zone—Liquid is shed from the back side of the slug and forms a film of length lf below a gas zone. 

The gas zone—A gas bubble is trapped between consecutive slugs, riding on top of the liquid film. 

ABSTRACT The Mallik gas hydrate field represents an onshore permafrost-associated gas hydrate accumulation in the Mackenzie Delta on the coast of the Beaufort Sea, Northwest Territories, Canada. This deposit contains a high concentration of natural gas hydrate with an underlying aquifer or free-gas zone at the base of the hydrate stability field. The physical and chemical properties of CH4 and C02 hydrates indicate the possibility of coincident C02 sequestration and CH4 production from the Mallik gas hydrate bearing zones. This study presents a numerical assessment of C02 sequestration and the recovery of CH4 from the gas hydrates at the Mallik site, Mackenzie Delta, Canada. 

Diverter - The part of the bell nipple at the top of a marine riser, that controls the flow of gas or other fluids that may enter the wellbore under pressure, before the BOP stack has be set in place. It is used when drilling through shallow underground gas zones for diverting gas kicks in deep high pressure zones. 

Figures 4.6—4.8 are the results for the stoichiometric propane-air flame. Figure 4.6 reports the variance of the major species, temperature, and heat release Figure 4.7 reports the major stable propane fragment distribution due to the proceeding reactions and Figure 4.8 shows the radical and formaldehyde distributions—all as a function of a spatial distance through the flame wave. As stated, the total wave thickness is chosen from the point at which one of the reactant mole fractions begins to decay to the point at which the heat release rate begins to taper off sharply. Since the point of initial reactant decay corresponds closely to the initial perceptive rise in temperature, the initial thermoneutral period is quite short. The heat release rate curve would ordinarily drop to zero sharply except that the recombination of the radicals in the burned gas zone contribute some energy. The choice of the position that separates the preheat zone and the reaction zone has been made to account for the slight exothermicity of the fuel attack reactions by radicals which have diffused into...

Prompt NO mechanisms In dealing with the presentation of prompt NO mechanisms, much can be learned by considering the historical development of the concept of prompt NO. With the development of the Zeldovich mechanism, many investigators followed the concept that in premixed flame systems, NO would form only in the post-flame or burned gas zone. Thus, it was thought possible to experimentally determine thermal NO formation rates and, from these rates, to find the rate constant of Eq. (8.49) by measurement of the NO concentration profiles in the post-flame zone. Such measurements can be performed readily on flat flame burners. Of course, in order to make these determinations, it is necessary to know the O atom concentrations. Since hydrocarbon-air flames were always considered, the nitrogen concentration was always in large excess. As discussed in the preceding subsection, the O atom concentration was taken as the equilibrium concentration at the flame temperature and all other reactions were assumed very fast compared to the Zeldovich mechanism. 

Solid materials are often dried or heated using combustion gas exhaust from a fired heater as the material is conveyed through a hot combustion gas zone. Solids handling dryers may take a number of forms, e.g., a rotary kiln. Losses involving dryers usually involve internal fires or explosions. 

A deflagration wave formed by a reactive gas under one-dimensional steady-state flow conditions is illustrated in Fig. 3.7. In the combustion wave, the temperature increases from the initial temperature of the unburned gas to the ignition temperature and then reaches the flame temperature. The heat generated in the reaction zone is transferred back to the unbumed gas zone. 

The thermal balance of the heat flux transferred back from the reaction zone to the unburned gas zone and the heat supplied to the unbumed gas to increase its temperature from the initial temperature Tq to the ignition temperature Tj, is represented by... 

Lease condensate is much the same as condensate produced in cycling or gas field plants, except that the plant product contains more pentanes and hexanes. Mere separation of the well stream from a high pressure gas zone does not effect complete recovery of the lighter liquids. 

Possibly, a reservoir could be discovered with the oil at its bubble point with a gas zone so small that it would be difficult to identify. Normally, if no gas cap is present, the initial reservoir pressure is above the bubble-point pressure of the oil. 

The use of a wetted spherical model affords the opportunity of studying combustion under steady-state conditions. Forced convection of the ambient gas may be employed without distortion of the object. Sufficiently large models may be employed when it is desired to probe the gas zones surrounding the burning sphere. It is apparent that the method is restricted to conditions where polymerization products and carbonaceous residues are not formed. In the application of such models, the conditions of internal circulation, radiant heat transmission, and thermal conductivity of the interior are somewhat altered from those encountered in a liquid droplet. Thus the problem of breakup of the droplet as a result of internal temperature rise cannot be investigated by this method. 

Hydrate formation from gas dissolution of rising water Hyndman and Davis (1992) proposed that as methane-unsaturated water rises, it becomes saturated at lower pressures. As the saturated (or supersaturated) water passes through the phase stability zone, hydrate formation occurs without a free gas zone. This model results in a maximum hydrate concentration at the three-phase (BSR) boundary with a successively lower hydrate amounts above the BSR as was shown to be the case in Cascadia Margin ODP Drill Sites 889 and 890 by Hyndman et al. (1996). 

Dual induction In the shallow penetration log, a higher resistivity is obtained relative to a free gas zone due to hydrate dissociation. This is a very tricky interpretation problem with Rw changing, and gas and hydrate both being insulators. The deep induction log shows high resistivity and mimics an ice-bearing reservoir. However, this log is confounded by Rw changing, and by gas and hydrate both being insulators... 

In the RCC process (Figure 8-13), the clean regenerated catalyst enters the bottom of the reactor riser where it contacts low-boiling hydrocarbon lift gas which accelerates the catalyst up the riser prior to feed injection (Hydrocarbon Processing, 1996). At the top of the lift gas zone the feed is injected through a series of nozzles located around the circumference of the reactor riser. 

Equation summary. As an attempt to clarify, I offer this further explanation the curve of Eq. (4.13) will derive the CD drag force constants of both Eqs. (4.9) and (4.10). The Eq. (4.13) CD drag force offers both this same range of Reynolds number coverage, and also extends beyond Eqs. (4.9) and (4.10), especially in the gas-phase zone. Remember also, Eq. (4.13) is applicable in either the liquid or gas zones and is suggested to... 

Semi-hermetic tandem pumps are also used for supercritical gases, in the same way as tandem pumps are used for high system and discharge pressures as described in Section 5.3. In order to separate the liquid-filled rotor compartment from the gas zone, the pump is fitted with two mechanical seals. Accordingly, fluid can no longer be fed from pump 1 to pump 2... 

Clearly when K = 0, the two direct exchange areas involving a gas zone g[ j and g gj vanish. Computationally it is never necessary to make resort to Eq. (5-155) for calculation of gg,. This is so because sj, gSj, and gg may all be calculated arithmetically from appropriate values of StSj by using associated conservation relations and view factor algebra. 

It may be proved that the Q and S vectors computed from Eqs. (5-162) and (5-163) always exactly satisfy the overall (scalar) radiant energy balance Im Q = lJ)-S. In words, the total radiant gas emission for all gas zones in the enclosure must always exactly equal the total radiant energy received at all surface zones which comprise the enclosure. In Eqs. (5-162) and (5-163), the following definitions are employed for the four forward-directed exchange areas... 

The Limiting Case M = 1 and N = 1 The directed exchange areas for this special case correspond to a single well-mixed gas zone completely surrounded by a single surface zone A2. ffere the reflectivity matrix is a 1 x 1 scalar quantity which follows directly from the... 

Prompt NO mechanisms In dealing with the presentation of prompt NO mechanisms, much can be learned by considering the historical development of the concept of prompt NO. With the development of the Zeldovich mechanism, many investigators followed the concept that in premixed flame systems, NO would form only in the post-flame or burned-gas zone. Thus, it was thought possible to experimentally determine thermal NO formation rates and, from these rates, to... 

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