Oxygen quasi-steady

In a short time period, the dynamic model shown in Equation (3.13.1.1) at quasi-steady-state condition, OTR to microbial cells would be equal to oxygen molar flow transfer to the liquid phase.4... 

If the fuel responds fast to the compartment changes, such a quasi-steady burning rate model will suffice to explain the expenditure of fuel mass in the compartment. The fuel heat flux is composed of flame and external (compartment) heating. The flame temperature depends on the oxygen mass fraction ( Yq2 ), and external radiant heating depends on compartment temperatures. 

Verhallen P.T.H.M., Oomen L.J.P., v.d.Elsen A.J.J.M., Kruger A.J., and Fortuin J.M.H. (1984) The diffusion coefficients of helium, hydrogen, oxygen and nitrogen in water determined from the permeability of a stagnant liquid layer in the quasi-steady state. Chem. Eng. Sci. 39, 1535-1541. 

If during the beginning of the experiment the fermentation is at a quasi-steady state, that is the growth rate is such that the biomass concentration X may be considered to be constant during the experiment, then a material balance for the oxygen gives ... 

Similarly, the quasi-steady oxygen weight fraction profile in the gas phase subject to the boimdary conditions in Equations 11 and 12 is ... 

In keeping with the assumptions of the classical quasi-steady droplet combustion models by Spalding (I) and Godsave (2), the combustion process is assumed for this investigation to take place instantaneously at a fiame surface where the fuel and oxygen react stoichiometrically and completely. Then the rate at which fuel is reacted at a fiame surface located at r = b can be expressed in terms of the delta function by ... 

Actually, we found that w° (wbm, iron(II) complexes,) [Cat]12, and wf [Cat], and linear radicals termination on catalyst may be not taken into account [22], With allowance for quasi-steady-state conditions for R02 radicals the calculated by formula (1) wterm= vr, can be considered a measure of activation of molecular oxygen with iron(II) complexes. Discrepancy between wAP+MPc and wterm in the case of absence of linear termination of chain is connected with additional formation of alcohol and ketone at the stage of chain propagation Cat + R02 (2) ... 

The rate has been obtained from the initial rate of internal oxidation of Ag-Cd alloys involving 1 % Cd. When a Ag-Cd alloy is exposed to oxygen at 400°C, oxygen is dissolved in form of atoms, diffuses into the interior of the alloy, and reacts with Cd atoms under formation of a precipitate of CdO in metallic silver as matrix. The reaction may be followed by volumetric measurements of the consumption of gaseous oxygen. Under quasi-steady-state conditions, the rate of formation of oxygen atoms by dissociation of O2,, must equal the rate of diffusion... 

Assuming a quasi-steady state for active species, when chain lengths are large (>>100), the rate of oxygen absorption, which must not be confused with the rate of propagation, is written, no matter what the partial oxygen pressure may be, as... 

Simple transient state experiments in laboratory plug flow reactors can qualitatively tell whether the surface processes mentioned above are instantaneous or not. For example, a step composition change can lead to two types of results. Either the outlet composition follows what is expected from tlie steady state rate equations or not. In the fonner case, one may assume quasi steady state. In the latter case, one is facing a slow surface step (oxidation/reduction of rhodiiun, oxygen storage/release, transient deactivation by SO2, etc.) that affects the main reaction mechanism. 

The quasi-steady approximation requires the assumption that the dissolved oxygen concentration varies linearly across the zone of internal oxidation. Therefore, the oxygen flux through the internal oxidation zone (lOZ) is given by Pick s first law as Equation (5.3),... 

The explosion limit phenomenology observed in hydrogen-oxygen mixtures has been semi-quantitatively described in section 2.1.2. For an initial pressure below approximately one atmosphere there exists one threshold temperature for explosion, typically between 700 and 900 K, whose magnitude is determined by the appropriate isothermal branched chain kinetics. More specifically, this boundary, separating regimes of slow, quasi-steady state and explosively rapid reaction, is defined by an equality between the rates of chain centre formation by branching steps and destruction by termination steps. 

This implies that the spray tends to approach a saturation state unless additional heat and oxygen are supplied from the outside of the spray stream. It also implies that the behavior of the outer diffusion flame dominates the subsequent evolution of spray combustion from the spray boundary side. In real spray combustion, this boundary-layer type of change occurs dynamically because the boundary of the spray stream is located in the coherent vertical structure of the shear layer. In addition, turbulent effects are inevitable. However, such fluid dynamic effects have not yet been well characterized. Therefore, we focus on the behavior of the outer diffusion flame based on a quasi-steady continuum spray model. Chiu s theory is developed on this basis to classify the combustion modes excited by the penetration of the outer diffusion flame into the spray region. 

We can obtain a better understanding of the physico-chemical process by simplifying the rate equations in the following way. We note that the oxygen solubility in iron is low, and thus the corresponding rate constant U (see eq. (9-31)) is relatively small. Consequently, for a quasi-steady state process, Ax A since the diffusional resistance of Fe per unit thickness is much greater than that of wiistite. It then follows from eqs. (9-32) and (9-33) that 7o(Fe) 7pe(FeO). Eq. (9-33) can thus be written as ... 

This picture is further complicated by the investigations of Schuldiner and Warner,who found that hydrogen and oxygen are readily absorbed into the platinum surface. Thus by cycling a platinum electrode into hydrogen or oxygen evolution, the surface structure of the metal would be changed. Thus the time necessary to obtain a quasi-steady-state surface area will depend on the potential limits of the cycle. This has not, however, been defined in cyclic voltametric studies and the assumed reproducible surfaces have not been satisfactorily demonstrated. The work of Will and... 

This paper considers a heat transfer system during this quasi-steady state period only. Figure 1 depicts a cross section through a part of a container wall, on one side of which is liquid oxygen, boiling at atmospheric pressure the other side is exposed to the atmosphere. 

Figure 8 Quasi steady state polarization curves 1(E) of oxygen reduction at a AulPAnilFePc rotating disc electrode in 0.5 M H2SO4 (25 °C 2 mV s ).

FIGURE 5 The time constants for the obtaining quasi-steady-state for the oceans. The caicuiation assumed a -i-8 initial ocean whose isotopic composition is driven by the competition between chemicai weathering and hydrothermal activity on the seafloor. The inset shows the haif-iife of any perturbation in the oxygen isotope composition of the oceans. For geologically plausible choice of rates, the ridge process dominates the oxygen isotope composition of the oceans. 

The composite flux method with quasi-steady-state assumptions has been used in studies of hydrogen-oxygen-nitrogen flames (Dixon-Lewis, 1979a) and of a hydrogen-air flame inhibited by hydrogen bromide (Dixon-Lewis, 1979b). However, the same order of accuracy is now obtainable by the finite-element technique described in Section 6.2. 

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