Operating Flux

The peak operating flux density (Umax) should never closely approach or enter saturation over the power supply s entire operating range. 

Fc is the volume of the eore (Cm ). is the switehing frequency (FIz). is the maximum excursion of the operating flux density. 

Checking the maximum operating flux densities using Faraday s law, at light load, the frequency is approximately 1 MHz, the is 211G. At its heavy load (200kHz) the is 1,100G. This seems to be exactly what is required. 

The major losses within any core material are the hysteresis loss and eddy current loss. These losses are typically lumped together by the core manufacturer and given in a graph of watts lost per unit volume V5. the peak operational flux density (5max) and frequency of operation. Hysteresis loss is given as... 

The reactions of Fig. 1 are not in contention. The enzymes and intermediates of Figs. 2 and 4 are probably present in most tissues, particularly where Aid activity is greater than that of TA. No secure evidence exists, however, that the individual reactions of either Figs. 1 or 2 are so linked that they constitute a metabolic pathway, with a flux generating step, ordered reactant, and end-product stoichiometry or fixed direction of operational flux. Nor is there a basis for belief that the PPP can operate as... 

A change in a core response, such as power density, at a core location T is related to the current estimates of the governing system operators, flux and eigenvalue through the following GPT functional ... 

For most ferrites, an operating flux density of 0.25 T is acceptable, since the saturation flux density is typically around 0.3 T. 

For the 10 kDa membrane no substantial flux decline is observed. These results are summarised in Figure 6.29. The 10 kDa membrane also has a much lower pure water flux and operational flux. The fluxes of the 10 kDa and 100 kDa membranes are verj similar at a calcium concentration of 4 mM 50 and 63 Lm h for the 100 kDa and 10 kDa membranes, respectively. It should be noted that the transmembrane pressures were 100 kPa (100 kDa) and 300 kPa (10 kDa). The effect of flux on fouling... 

The efficiency of backshock can be assessed based on the ratio of the filtrate volume obtained during the filtration period to the volume of permeate lost during the backshock period in a working cycle. The ratio of gained and lost filtrate volume is a function of backflush frequency, the period of backflushing, the operation conditions, and the properties of the foulant materials. A high operational flux usually needs a strong backflush, which may correspond to an increased loss of permeate volume, to maintain stable performance. Therefore, the backflush conditions need to be optimized in order to maximize the productivity of the process. 

The particular function of the MOR is to manage reactor control over. the considerable range between JYf (full operating flux) and (about 1% of Nf).. 

The control vector u consists, in this example, of a single element, the flux (j). There are constraints on (j), for certainly it cannot be negative, nor should it exceed some largest value, maximum power. Usually would be the same as the normal operating flux. We therefore indeed have a problem with control constraints. 

The designer of the RO system chooses the flux rate it is not a property of the membrane. In general, the flux that an RO system is designed for should be a function of the influent water quality. This is because higher flux results in more rapid fouling of the membranes. So, the lower the influent water quality, the lower the operating flux of the RO system should be. Table 3.3 shows the recommended flux as a function of influent water source (which is an indirect measure of the water quality) and silt density index (SDI), which is a measure of the tendency of water to foul a membrane (See Chapter 3.9). When in doubt, a default flux of 14 gfd is usually recommended. 

For a natural uranium reactor, where the possible excess reactivity is limited by the low value, it may not be possible to overcome the peak in the transient, and it will then be necessary to wait for some time after the peak is reached before the reactor can be started up again. One way of avoiding such a situation, employed in the CANDU heavy water reactor, is the use of booster rods of enriched uranium which can be inserted into the core to provide a temporary increase in reactivity. For any reactor with a limited capacity for xenon override, it is desirable to restart after an unscheduled reactor trip as soon as possible, before the xenon transient has had a chance to build up. The re-establishment of the xenon burn-out due to restoring the operational flux level then allows the equilibrium xenon concentration to be regained without any large change in the reactivity having taken place. 

Figure 6.24 Fractional deposition of humic acids at different operating fluxes. The intercepts on the x-axis indicate the critical fluxes.

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