Dryout time

Warm-up times can be considerably less than dryout times, if no moisture needs to be driven off. Some warm-up time is important even for previously dried-out furnaces to minimize refractory spalling because of too-rapid or uneven thermal expansion of the dry, solid refractory. 

Q3. What is the difference between dryout time for a newly installed refractory and warm-up time for a previously dried furnace ... 

Performance Requirement - Load Follow Capability - SG Dryout Time - Daily load follow - Relaxation of dryout time to 20 minutes -Excluding frequency control - Related to PSCS removal... 

In general, the term dryout indicates a local continuous contact of the gas phase with the surface. This term contains no statement as to the average (either spatial or temporal) value of the surface temperature at which dryout may occur. The term used in the present study is defined with respect to the averaged viewpoint of the process time. 

It may be used, the relation of the time-averaged heat transfer coefficients on the top and bottom, as a criterion for determination of dryout. It was assumed that the relation he/hi < 1 indicates dryout, i.e., the surface superheat Tw -7f is greater than that, when the surface contacts single-phase water only (hg is the heat transfer at the bottom of the channel). This method can be applied to connect dryout with hydraulic conditions, if the value of he may be associated with intermittent flow parameters. 

One of the more common difficulties in bonding pine veneers and chips is adhesive dryout. Dry-out is associated with the high liquid absorbancy of pine sapwood and it appears especially during long assembly times. This problem can be overcome by using resins modified through reaction with alkylated phenols, especially 3,4-xylenol [52]. Another technique used to achieve similar results is the manipulation of synthesis procedures used in preparing a standard PF resin [52]. The dry-out resistance imparted by alkylated phenols is due to an initial semithermoplastic character in the resin. This is derived from their monomer bifunctionality and the linear polymer that is consequently formed. 

With thick rigid refractory linings, there is danger of fracture from shock thermal expansion when they are cold and suddenly filled with molten liquid thus, they are usually preheated before every filling. The dryout burners also are usually used for preheating, but a different time-versus-input program should be used. It is wise to seek the advice of the refractory supplier or both dryout and preheat cycle timing. 

Warning When using burners for dryout or warm-up operations, do not skimp on adequate flame safety and programming just because you think this is a temporary operation. Too many new furnaces have never produced a nickel because of start-up explosions. The most dangerous times for furnaces are, as with airplanes, (pardon the expression) during takeoff and landing. 

This can cause a temporary dryout on the anode side of the membrane and hence a jump in membrane resistance or a sharp decrease in cell voltage. This voltage drop is, however, recoverable within a period of the time constant that is characteristic of water back-diffusion through the membrane. 

The second functional event AC-0.5HR in the station blackout event tree is related to the restoration of electrical power to the plant safety buses before the dryout of the coolant on the secondary side of the steam generator, assessed from the wide range level, and start of the core heat up. Period of 30 min is assumed to be available for restoration of power in the PSA model for this functional event (Volkanovski and Prosek, 2013, Bertucio et al., 1990). The successful mitigation of the transient is related with power restoration within first 30 min results in successful mitigation of the transient, regardless of other failures, except criticality, in that time period. 

Of the earlier experiments, 3 and 4 were tests of wire wrapped fuel pins which featured In the fuel design at that time. Experiment 3 failed by local dryout downstream of a wire wrap at a position Just above the peak rating. This, together with adverse heat transfer test results and fretting behaviour, led to the change to wear pads and spacer grids. Most of the more recent irradiations, apart from experiment 12, have used NH, dosed coolant. No excessive cruddlng has been seen In any of the series, and deposition appears to... 

Pool scrubbing is produced in the secondary side of the broken steam generator, starting with the gap release, at 8276 s, and ending the dryout of the failed steam generator at 16401 s. During this time, 7.5 Kg of materials, most of it Cs(OH), are retained, as given in table 4.3.2.3. Nevertheless, it is considered that the SPARC model in MELCOR does not properly represent the complicated phenomena taken place under such accidental conditions. 

This is a state of water depletion, or drying of the fuel cell. Liquid stored in the electrolyte, DM, catalyst layer, and channels will be depleted with time. Eventually, this condition will result in a dryout of the membrane and greatly reduced performance. A net balance is, of... 

The effectiveness of EIS can be greatly enhanced with the use of a reference electrode, which has a stable potential at the time of measurement [3]. A suitable reference electrode allows discernment of the different electrode losses from the overall cell response, resulting in a more appropriate equivalent circuit. Ideally, the collective responses of the anode and cathode will add to the full cell resistance. Because the use of a stable reference electrode in many fuel cell systems is difficult, one common way to examine fuel cell behavior is the use of a dynamic hydrogen electrode (DHE). In this case, one of the electrodes is used as the DHE, with hydrogen flow at this location. It is assumed that the losses associated with the DHE are minor, and all polarizations measured can be attributed to the other electrode. This approach can be dubious and is not appropriate when there are phenomena at the DHE that can affect losses, such as anode dryout in a PEFC. Note that the DHE does not have to be the actual anode in the fuel cell but can be used at either electrode to examine the polarization of the opposing electrode. For example, a DHE can be used at the cathode of a DMFC to examine the polarization behavior of the anode in the DMFC. In this case, of course, the reaction does not galvanically proceed in the desired direction, and external power from a galvanostal/potentiostat system must be applied to drive the reaction in the desired direction. 

The requirement for both dynamic and static instabilities is that the increase in the two-phase pressure drop should be either equal to or greater than the decrease in the single-phase pressure drop as the inlet flow decreases. The relevant limit is actually the static (non-linear) instability boundary, which may lead to CHF, has been called the "zeroth mode" of dynamic instability. Thus, in dynamic dispersion-type analysis, it corresponds to the time-independent, zero-frequency (or infinite wave number), real wave number case which, corresponds precisely to the homogeneous equilibrium limit for the flow. In non-linear (called excursive instability ), the channels could switch from one flow rate to another while maintaining the same total pressure drop. When non-linearly unstable, the channel flow fluctuates, or reverses, and dryout can ensue. ... 

All the reported data relate to conditions where core power equals SG removed power. This is also valid when dryout situations occur and testifies of the small excursion of rod surface temperature. The excursion is actually limited to a few tens of Kelvin and is stable as a function of time. The main comments to the achieved results are ... 

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