Fractional power transfer

Figure 7.7 Fraction power transfer for a 1-1-8 laser mixture [41].

Figure 41 from Ref.34) gives the fractional electron power transfer to the different excitation processes in pure C02. Fractional power transfer is a unique function of E/N and is also independent of both ne and NCo2. 

Fd(E/N) is the fractional power transferred to dissociative electronic excitation at a given E/N, as derived from Fig. 41, W is the electric power density transferred to the discharge (W cm-3) and 6.7 x 105 J mol-1 is the 7 eV threshold energy of process XLIV, N°o2 is the initial number density of C02. The experimentally determined degree of C02 dissociation zd at the exit of the discharge zone of length 5 has been fitted by a first order equation with volume variation... 

The amount of interfacial transfer area created by the action of the flowing gas on the liquid is proportional to some fraction of the power transferred from the gas per unit volume of liquid. 

Effects of Temperature on kG and k, The Stanton-number relationship for gas-phase mass transfer in packed beds, Eq. (5-301), indicates that for a given system geometry the rate coefficient kG depends only on the Reynolds number and the Schmidt number. Since the Schmidt number for a gas is approximately independent of temperature, the principal effect of temperature upon kG arises from changes in the gas viscosity with changes in temperature. For normally encountered temperature ranges, these effects will be small owing to the fractional powers involved in Reynolds-number terms (see Tables 5-17 to 5-24). It thus can be concluded that for all... 

In the previous sections, stagnant films were assumed to exist on each side of the interface, and the normal mass transfer coefficients were assumed proportional to the first power of the molecular diffusivity. In many mass transfer operations, the rate of transfer varies with only a fractional power of the diffusivity because of flow in the boundary layer or because of the short lifetime of surface elements. The penetration theory is a model for short contact times that has often been applied to mass transfer from bubbles, drops, or moving liquid films. The equations for unsteady-state diffusion show that the concentration profile near a newly created interface becomes less steep with time, and the average coefficient varies with the square root of (D/t) [4] ... 

Two-dimensional CE instrumentation is more complicated, with two power supplies, one for each capillary (Figure 21.18). The sample undergoes separation by CSE. Fractions are transferred between capillaries by manipulation of the voltages applied across the two capillaries. 

This equation is used to estimate the mass transfer coefficient at liquid-solid interfaces in packed towers, and it might be the best available correlation for liquids. Note that in this equation the reciprocal Schmidt number is raised to a positive fractional power. 

The energy E is expressed in electronvolts (eV), or kiloelectronvolts (keV). If the cathode-to-anode voltage is 50 kV, the electron impinges on the anode with a kinetic energy of 50 keV. Most of the power transferred to the accelerated electrons is dissipated as heat in the anode, and only a small fraction of the power results in the emission of x-rays. TVo important types of x-rays are produced bremsstrahlung and characteristic x-rays. 

Consequently the fraction of total power transferred between the two fibers is F, and the beat length z, = InFIC. Using the figures from the previous section a 1 % difference in core radii of the two fibers results in a maximum exchange of 10% of total power. We consider this problem again in Chapter 29. 

An important application of the solution of the coupled local-mode equations for weak power transfer determines how slowly a waveguide must vary along its length in order that an individual local mode can propagate with negligible variation in its power. If we assume the /th local mode alone is initially excited with unit power, i.e. h((0) = 1, then the fraction of power excited in the jth... 

Thus a fraction F of the total power is exchanged between the two modes and the beat length is InFIx. At the resonance of Eq. (28-21), F = 1/2, and 50 per cent power transfer occurs. We emphasize that the solution, Eq. (28-23), is only accurate at, or very close to, resonance. This situation minimizes the power loss to radiation and to the backward-propagating fundamental mode. 

Fig. 29-2 (a) Normalized coupling coefficient of Eq. (18-42) as a function of the normalized separation d/p for a pair of identical step-profile fibers, (b) Fraction of total power transferred between step-profile fibers with slight difference dp in their core radii. 

When dp is due to radius variations only, it follows from Eqs. (29-8)and (18-42) that the fraction of total power transferred between the fibers is... 

We can estimate the power transfer if the emissivities are near unity each surface radiates a power given by the Stefan-Boltzmann law, and each absorbs a large fraction of that power, so the net power transmitted is approximately... 

The terms dryout occurrence appear in the right part of Fig. 1, when primary system mass inventory is roughly lower than 40% of the nominal value. Dryout is caused by the combination of low flow and high void fraction. As a consequence, film boiling heat transfer regime is experienced with low coefficient for heat transfer. Rod surface temperature increases in various zones of the core and the overall process of thermal power transfer from fuel rods to the fluid may become unstable. The system operation in these conditions is not acceptable from a technological point of view. It may be noted that the temperature excursion is strongly affected by primary system pressure and thermal power levels the linear rod power plays a role in these conditions. At primary system pressure around 15 MPa (nominal operation for PWR), post-dryout surface temperature jumps may be as low as a few tens of Kelvin, tolerable for the mechanical resistance of the rod-clad material. 

When the gas velocities are increased, both the Reynolds number and the Nusselt number would increase, while the ratio Nu/Re decreases with (Re) to the —0.4 to —0.6 power. An increase in gas velocities would improve on the heat and mass transfer coefficients from gas to wall, but would also increase the fraction of heat that is not given up to the wall and the fraction of benzene that never goes near the wall due to the reduction in residence time. 

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