Velocity, high coolant

Figure 9. High coolant velocities in unclogged tubes of radiator section caused impingement attack and penetrating failures.

If care is taken in the panel design to prevent low velocity regions near the tops of panels, which can become easily blocked by vapor, and if a sufficiently high coolant velocity is used (>1 m/s... 

In DCMD, increase in flow rate increases the permeate flux. The shear force generated at high-flow rate reduces concentration polarization. Banat [64] found that the flow rate of cooling water had minimal effect on the permeate flux. Ohta [65] has shown that an increase in coolant velocity from 0.02 to 0.08 m s resulted in 1.5-fold increase in the permeate flux. In the same study, it was found that an increase in velocity of hot feed increased the flux by twofold. 

The high surface to volume ratio of spherical fuel elements ensures excellent heat transfer conditions, which results in low maximum and average fuel temperatures. In case of a coated particle fuel, the situation is even more favourable, since such fuel is designed to operate at very high temperatures. The coolant velocity is about 16 cm/sec. The core is cooled by forced convection, but the residual heat produced in the fuel chamber is removed by natural convection. 

MCST [12,13]. For high temperature reactors, the coolant enthalpy rise in the core is high and coolant flow rate is inevitably low. The gap between fuel rods is kept small to increase the coolant velocity in the core. 

The coolant flow velocity, which is usually determined by flow experiments, has been limited in LMFBR designs in order to prevent excessive vibration of the fuel rods. Smaller fuel rod diameters are advantageous for a high power density concept with fixed average linear heat rate, but this concept requires more mass flux to keep the cladding surface temperature below the limit. High mass flux, that is, high flow velocity, raises a concern of FIV. 

Severe corrosion by turbulent mill coolant was found generally throughout a rolling-oil system. Hose couplings were severely wasted in as little as 8 weeks (Fig. 7.23A and B). Turbulence caused by high-velocity flow through nozzles accelerated attack. Attack at bends, elbows, intrusive welds, and discharge areas was also severe. 

Coolant flow is set by the designed temperature increase of the fluid and needed mass velocity or Reynolds number to maintain a high heat transfer coefficient on the shell side. Smaller flows combined with more baffles results in higher temperature increase on the shell side. Reacting fluid flows upwards in the tubes. This is usually the best plan to even out temperature bumps in the tube side and to minimize temperature feedback to avoid thermal runaway of exothermic reactions. 

Reactor coolant primary circulation system Depending on design, this closed-loop cooling system may recirculate high-purity treated water or other fluid at 300,000 to 450,000 US gpm (1,136-1,704 m3/m), and at velocities of 15 to 16 ft/s 4.5 to 4.9 m/s. 

The constricted orifice of the concentric quartz wall directs the coolant argon along the outer wall of the torch (Figure 1). The low-pressure region, generated by the Bernoulle effect from the peripheral high-velocity gas flows, centers the plasma, cans-... 

Contact condensers employ liquid coolants, usually water, which come in direct contact with condensing vapors. These devices are relatively uncomplicated, with typical configurations illustrated in Figure 14. Some contact condensers are simple spray chambers, usually with baffles to ensure adequate contact. Others, incorporate high-velocity jets designed to produce a vacuum. 

HYLIFE Lithium Flow. The lithium jets are injected into the 8-m-high HYLIFE chamber with 9.5 m/s initial velocity (72.2 m /s flow rate). Additional coolant in the neutron reflector increases the flow to 86.2 m /s. The mixed-mean temperature rise in the lithium is 18 K, and the peak lithium temperature is 500°C. Eleven recirculation pumps, each with 7.8 m /sec (124,000 gpm) capacity, return the lithium to the top of the vessel. About 9.8 m /s is diverted from the flow loop to four Li-Na intermediate heat exchangers which in turn drive twelve steam generators. The plant gross electric power is 1236 MWg 135 MW is used to drive the 4.5 MJ - 5 % efficient laser, 95 MW is used elsewhere in the plant, and 1006 MW is the net power. 

In operation, the sample container is attached to the joint on the Till pot, and the entire column is evacuated down to the stopcock on the sample container. The still pot is cooled in liquid nitrogen, and the sample is allowed to distill into it. The stopcock on the still pot is closed, and a Dewar is placed around the latter. A small amount of heat is then supplied by the heater, and the pressure in the column is allowed to increase. When the desired operating pressure, which should be fairly high in order to decrease the vapor velocity in the column, is reached, the coolant is supplied to the condenser at such... 

Cavitation corrosion of cylinder liners is not caused by high velocity water flow, nor by impingement of coolant streams. Rather, it appears that vibratory effects are primarily responsible. Under the tremendous stresses of fuel compression and combustion in the Diesel cycle, these 3/4 inch thick cylinder liners vibrate or "ring" at frequencies estimated to be in the range of 7,000 to 8,000 cycles per second, and higher. 

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