Forced-circulation loop

Fadavi, A., and Chisti, Y. (2005), Gas-liquid mass transfer in a novel forced circulation loop reactor, Chemical Engineering Journal, 112(1-3) 73-80. 

Fadavi, A., Chisti, Y., and Chriascarontel, L. (2008), Bubble size in a forced circulation loop reactor, Journal of Chemical Technology Biotechnology, 83(1) 105-108. 

On top of the prestressed concrete vessel there is a steel vessel extension which is fixed by means of separate tendons anchored to the bottom of the concrete vessel. This extension contains the pipe nozzles for the hot and cold leg pipes, for the forced circulation loops of the reactor pool cooling system, and for some other system pipes. It also encloses the upper riser plenum, and the pressurizer. 

The closed cooling water system consists of a separate, forced circulation loop. This system uses water piped from the site service water source to provide a heat sink for selected nuclear system equipment. Its purpose is to provide a second barrier between the primary systems containing radioactive products and the service water system that is the final heat... 

Loop AT—There must be a difference in temprerature in a forced circulation loop system to provide the drivirrg force for solution-controlled mass transpxrrt. 

All these crystallizers are equipped with a forced circulation loop that serves to keep the supersaturation within the metastable zone, that is, serves to avoid spontaneous nucleation. 

Pump loops. An in-pile loop [1.1] is similar to all forced-circulation loops it consists of i pump, pressurizer, circulating fines, heaters and cook rs,. and associated control and proce.ss e quipment. The circulating pump, designed at ORXL [14-10], is a caniuHl-rotor type which delivers 5 gpm at a 40-ft head at prc.ssurijs up to 2000 psig. 

Descriptions of Inconel Forced-Circulation Loops Operated in the LITR and the MTR... 

Te.sts have also been made in which the fissioning fuel is pumped through a system in which a thermal gradient is maintained in the fluid. These tests included the Aircraft Reactor Experiment (described in Chapter 16) and three types of forced-circulation loop tests. A large loop, in which the pump was outside the reactor shield, was operated in a horizontal beam hole of the LITR, A smaller loop was operated in a vertical position in the LITR lattice with the pump just outside the lattice. A third loop was operated completely within a beam-hole of the MTR. f The operating conditions for these three loops are given in Table 12-8. 

Dynamic tests of the reaction between Bi and steel in the presence of a radiation field must be completed before a final selection can be made of materials for the LMFR. The effect of velocity on corrosion is not certain from the out-of-pile studies, so that no exact analogy can be made between out-of-pile forced circulation loops and in-pile capsules. There has been limited work done at Harwell [6] with thermal convection loops in and out of a radiation field. These loops had no U but did contain Ca and Zr inhibitors. The data suggest that pile radiation may have induced some acceleration of mass transfer. 

An in-pile, forced-circulation loop has been built at BNL and two others at Babcock Wilcox Research Laboratory to test the corrosion stability of LMFR materials under conditions to be expected in the reactor experiment. In this loop, Bi containiiif approximately 1500 ppm of 180 ppm Zr, and 850 ppm Mg will be pumped at a rate of 5 to 7 gpm. The bulk A2 will be approximately 75°C, with a maximum temperature of 500°C. There are three sample sections in the loop one, containing samples of 1 % Cr-1/2% Mo steel, 2 % Cr-1% Mo steel. Be, and graphite, will be at the center of the reactor and will be in a flux of approximately 3 X lO " thermal neutrons one within the shield will see delayed neutrons at a temperature of 500°C and the third section will be outside the reactor at a temperature of 425°C. This test is presently being assembled, and will be operating late in 1958. 

By cutting out a section of heated length of a Freon loop at the inlet and restoring the original flow rate, Crowley et al. (1967) found that the reduction of the heated length increased the flow stability in forced circulation with a constant power density. A similar effect was found in a natural-circulation loop (Mathisen, 1967). Crowley et al. (1967) further noticed that the change of heated length did not affect the period of oscillation, since the flow rate was kept constant. 

The heart of a forced circulation process is the neutralization loop (see Figure 10.2). It consists of a neutralizer, the vapor separator and the circulation pump. Due to its low investment costs, vacuum neutralization is chosen in most... 

Many solid circulation loops require that the standpipe or at least a portion of it be inclined to the vertical because of layout constraints. Therefore, an inclined conical moving bed is regarded as a generalized case for analysis. Axial force balance on an elemental slice of material shown in Fig. 21a gives... 

Not all crystallizers are agitated with impellers in the vessel itself in agitated tank configuration. A common arrangement is to use a pump (or an axial flow impeller in an external pipe) to generate flow in a loop external to, but drawing from, and discharging to the main vessel. Such crystallizers are known as forced circulation crystallizers. These are widely used, for example, in sodium chloride crystallization (see Chapter 5, section... 

Remedies for a leakage problem are discussed in Secs. 4.7 and 4.8. Remedies for a deficient liquid head are raising liquid level or cutting down pressure drop in the reboiler loop. If impractical, a forced-circulation reboiler should be considered. 

Bioreactors. Bioreactors that utilize hving cells are typically called fermenters. There are several different types of bioreactors mechanically stirred or agitated tanks bubble columns (cylindrical tanks that are not stirred but through which gas is bubbled) loop reactors, which have forced circulation packed-bed reactors membrane reactors microreactors and a variety of different types of reactors that are not easily classified (such as gas-Uquid reactors and rotating-disk reactors). Biochemical engineers must choose the best bioreactor type for the desired purpose and outfit it with the right instrumentation and other features. 

Fuller, C. J. and MaePherson, R. E., "Design and Operation of Stainless Steel Forced-Circulation Boiling-Potassium Corrosion-Testing Loops, Oak Ridge National Laboratory Report, ORNL-TM-2595, 1967. 

Cycle type Indirect cycle intermediate loop of forced circulation molten salt. Ca-Br thermochemical water cracking cycle/ supercritical CO2 Bra54on cycle with a feed-forward multi-effect distillation bottoming cycle... 

A forced circulation, ambient pressure fused salt (flibe) intermediate heat transport loop carries the heat from the in-vessel intermediate heat exchanger (IHX) to the balance of plant (BOP). Figure XXIV-4 shows the overall heat flow for the reactor and BOP at full power of 400 MW(th). 

The STAR-H2 reactor heat source drives a balance of plant through an ambient pressure, forced circulation, fused salt (flibe) intermediate heat transport loop. 

On the left hand side, it is shown a sketch of a (forced circulated) FC-type crystalliser, a crystalliser with external circulation loop. On the right hand side, one can find a simplified solubility system in which the metastable limit is marked with a dashed line. What happens within one circulation loop is indicated by numbers in the solubility diagram as well as in the FC-crystalliser sketch. 

A typical steam-generation thermosiphon circuit is shown in Exhibit 7-48. Briefly, this circuit is the difference of the water-steam mixture and the static head in the downcomer that maintains fluid circulation. Locating the steam drum at the top of the furnace provides the static head and collects the steam being generated Steam returns to the top portion of the drum, while the water lines come off die bottom. Loops and pockets must be avoided when layipg out die downcomer, and riser piping and any horizontal lines must slope toward the vwiste heat boiler or convection coil. Wh pumps are used in this circuit, it is called forced circulation. 

The rated thermal output of MONJU [5.63, 5.64] is transported through the primary heat transport system (PHTS) and intermediate heat transport system (IHTS) loops to the steam generators. Shutdown heat removal is normally by forced circulation (FC) provided by pony motors associated with each of the loop pumps. Heat is rejected to air at the air blast heat exchanger of the intermediate reactor auxiliary cooling system (ACS) which branches off from each IHTS loop. Thus the auxiliary cooling system (ACS) of the Monju reactor is coupled with the secondary system which also has the role as decay heat removal system. 

When the vessel is opened, especially during refuelling, decay heat is removed by the twelve RRPa cooled by chilled water to obtain a very low primary temperature compatible with the conditions of maintenance. The primary circuit operates in a natural convection mode and the RRPa loops operate with a forced circulation. 

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