Flux profile

Fig. 1. Vacuum evaporation process with use of electron beam heating where A represents the material to be deposited. The flux profile ( ) is at a...

A flatter flux profile provides wider safety margins than previous designs. 

All the references to burn-out have thus far been concerned with uniformly heated channels, apart from some of the rod bundles where the heat flux varies from one rod to another, but which respond to analysis in terms of the average heat flux. In a nuclear-reactor situation, however, the heat flux varies along the length of a channel, and to find what effect this may have, some burn-out experiments on round tubes and annuli have been done using, for example, symmetrical or skewed-cosine axial heat-flux profiles. Tests with axial non-uniform heating in a rod bundle have not yet been reported. 

This is derived by substituting from the heat-balance expression, Eq. (20). Now, the skewed-cosine heat-flux profile being considered gives a known functional relationship between the flux and the quality at any position along the channel. By equating this relationship with Eq. (35), a solution can be obtained giving the local values of (j> and k at the predicted burn-out position. The corresponding peak flux can then be evaluated, and in this way the predicted burn-out lines for the three mass velocities in Fig. 40 can be drawn. 

Fig. 40. Test of the Barnett local-conditions hypothesis applied to a tube with a skewed-cosine heat-flux profile [from Barnett (B4)]. Fluid water, d = 0.422 in., L — 12 in., P = 2000 psia.

Y = axial heat flux profile parameter Y = subchannel imbalance factor... 

Axial heat flux parameter Y The parameter Y, which replaces the heat flux shape factor in the CHF correlation, is not only a measure of the nonuniformity of the axial heat flux profile but also a means of converting from the inlet subcooling (AHin) to the local quality, X, form of the correlation via the heat balance equation. It is defined as... 

An approximate value of Yx at Z = Z, may be calculated by summing over a number of intervals of length. Thus, for a continuous axial heat flux profile, Yt is given by... 

Chopped cosine heat flux distribution For a heat flux distribution of a chopped cosine curve, the flux profile and the subcooled zone length are given by... 

The thickness, 8, was found to be insensitive to particle concentration, gas velocity and height within the furnace. That suggests that the thickness results from a balance of solids internal circulation which is generally much higher than netthroughflow. If the local solids flux profile,... 

Whenever it is necessary to measure reactor neutron flux profiles, a section of wire or foil is inserted directly into the reactor core. The wire or foil remains in the core for the length of time required for activation to the desired level. The cross-section of the flux wire or foil must be known to obtain an accurate flux profile. After activation, the flux wire or foil is rapidly removed from the reactor core and the activity counted. 

Fig. 8. SIMS profiles of 2H and nB in plasma-passivated B-implanted and annealed samples used in channeling studies of B—H complexes by Marwick et al. (1988). 1000 angstroms was etched off the surface of this sample to eliminate a layer containing a large excess of hydrogen. Nevertheless, some excess over the boron concentration remains at shallow depths. The histogram shows the deuterium profile used to analyze the data using calculated flux profiles.

Draw the concentration and flux profiles of a species i with surface concentration of 2 and bottom concentration of 10 (arbitrary units). Assume that the mixing length can be obtained from the distribution of conservative quantities, usually salinity or potential temperature. Craig (1969) suggests a value of 800m in the 4000m-deep Pacific. 

By market volume the most important flavour molecule is L-glutamic acid. In 2004, the worldwide annual MSG production was estimated to be amount 1,500,0001 [21]. The amino acid is extensively used as taste enhancer, frequently in conjunction with nucleotides, a flavour impression which is also referred to as umamf, a term derived from the Japanese meaning deliciousness or a savoury or palatable taste. MSG is manufactured by aerobic cultivation of Coryne-bacterium glutamicum on starch hydrolysates or molasses media in large-scale bioreactors (up to 500 m ). Production strains with modified metabolic flux profiles and highly permeable cell walls for an improved product secretion are... 

Determine the thermal-difffusive mass-flux profiles for all the species. Discuss the results in the context of the solution profiles. Which species have have important contributions to thermal-diffusive mass flux In what regions is the thermal diffusion important What is the direction of the thermal diffusion for the various species How does thermal diffusion compare in magnitude to ordinary diffusion for this problem ... 

By going one more step in approximating the concentration and flux profiles, a consistent second equation is obtained, yielding the pair of first-order partial... 

FIGURE 15.3 Instantaneous flux profiles of estradiol through human epidermal membrane during a three stage experiment. Electrical procedures were iontophoresis (0.8 mA/cm2), electroporation (5 x 100 Y pulses with a pulse width of 100 ms), or electroporation followed by iontophoresis (n = 5-9). 

The reduced solids flux profile, JVI/JV, can be empirically correlated by [Rhodes et al., 1992]... 

The mass flow distribution for various values of rj in horizontal pipe flows (y = 0) with Ndf of 0.01 and Knp of 0.1 is illustrated in Fig. 11.14, which is compared to the experimental data of Wen (1966). The figure shows that a higher tj gives rise to a sharper change in the mass flux profile, namely, a much higher mass flux at the bottom of the horizontal pipe... 

Munger J, Bennett BD, Parikh A et al (2008) Systems-level metabolic flux profiling identifies fatty acid synthesis as a target for antiviral therapy. Nat Biotechnol 26 1179-1186... 

FIGURE 14.6 Radiant heat flux profile in the LIFT. 

The gas flow to the radiant panel is set to obtain a heat flux at the 50 mm location that is 5-10kW/m2 above the critical heat flux for ignition (Section 14.3.2.3.2). The heat flux is verified with a heat flux meter inserted into a calcium silicate dummy specimen. The heat flux profile is shown in Figure 14.6 and can be used to determine the incident radiant heat flux at any location along the specimen center-line. The flux invariant may vary slightly and is usually determined for each apparatus during the initial calibration. 

Lysine Glucose Flux profiling in response to feedback deregulation of lysine biosynthesis [115]... 

Compared flux profiles of recombinant strains for efficient xylose uptake Bioethanol production [361]... 

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