Coolant turbulant-flow

Environment Mill coolant temperature 160°F (71 °C), turbulent flow... 

An alternative in cast molds is a large flood chamber (Figure 6.16). However, efficient water cooling requires turbulent flow and this may not be attained in a flood chamber or in large coolant channels (Chapter 17). Many small channels are better than a few large ones. The cooling circuits will normally be zoned so that different areas of the mold can be independently controlled. The coolant flow rate should be sufficient to ensure turbulent flow and to keep the temperature differential between inlet and outlet to about 3C. 

For prediction of subassembly coolant flow rate and temperature distributions a wide range of coolant flow and thermal convection regimes must be considered including laminar and turbulent flow natural, forced and mixed (forced + natural) convection and steady state and transient reactor conditions. 

If the coolant entered at 13°C, T would equal 8-0 and the heat-cooling effect. The overall heat transfer coefficient H) is made up of the sum of the reciprocals of the heat resistances including those of (/) the thin liquid layer dragging on the surface of the plate, because the Reynolds number is low or the surface is rough, (h) the plate itself, and Hi) any scale deposited on the plate and derived from protein or water hardness. Very significant reductions in the coefficient arise from (/) and more so from Hi). Therefore, from this standpoint, it is desirable to have very turbulent flow and clean plates. 

Another important consideration in cooling channel design is to ensure that the coolant circulates in turbulent rather than laminar (streamline) flow. The coefficient of heat transfer of the cooling system is drastically reduced in laminar flow. The condition of laminar or turbulent flow is determined by the Reynolds number (Re). This is a dimensionless number given by the equation ... 

For a channel of circular cross-section, turbulent flow occurs when the Reynolds number is greater than 2,300. The coefficient of heat transfer of the cooling system continues to increase as turbulence increases, so the design limit of the Reynolds number for cooling channels should be at least 5,000 and preferably 10,000. If the volume flow rate of the coolant remains... 

For turbulent flow existing in the coolant channels, the friction factor f, is determined by using /2/ ... 

Nu ist referred to the Nusselt number as a dimensionless parameter characterizu both the physical properties of the coolant and dynamic characteristics of the flow. For the turbulant flow in the cooling channels of the core, different empirical correlations for Nu are available. All correlations are expressed as a function of Reynolds number, specifying hydraulic condition and prandtl number Pr, for physical properties of the coolant. 

Within the assembly subchannels, the gravity-dominated, churn-turbulent coolant and air flows are sensitive to perturbations caused by air heatup and coolant cross flow to adjacent subchannels through the variable (0-40 mils) rib gaps. As a consequence, it is difficult to quantify local heat transfer conditions. A semi-empirical approach, based on separate effects (single heated wall) experiments, is being taken to establish the T/H criteria for the ECS phase. For restart, a conservative T/H precursor criterion to potential fuel damage conditions for the ECS phase power limit have been adopted. The criterion is as follows ... 

Another effect that has only recently been explored (11) is the cladding surface temperature fluctuations caused by interaction with the turbulent flowing coolant stream. Since the amplitude of these fluctuations may be of the same order as the temperature drop from the surface to the stream, some effect on the cladding metallurgical properties and corrosion resistance could result. 

The Brayton dimensions are sized for a lOOkWe Brayton, since two Braytons are operating at full capacity and one Brayton is a spare. The Braytons are oriented with the axis of the alternator parallel to the axis of the space ship boom to provide additional protection of the alternator s electrical sensors from reactor radiation. The Braytons are also oriented to avoid turbulent flow in the turbine to protect the thrust bearings and maintain efficiency. Figure 5-5 shows the base case Brayton design. The label numbers from Figure 5-5 correspond directly to the label numbers in Figure 5-6, a two dimensional schematic, which shows the path of the primary coolant through the primary components only. 

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. 

Dependences of length of cooling zone on annular flow rate Wa that is experimentally received (curve 1, Fig. 4.6) and calculated by equation (4.7) (curve 2, Fig. 4.6) are presented in Fig. 4.6. It is obvious that at low rates of annular flow (of coolant) significant discrepancy between experimental and calculated values of Lcooi is observed. At the same time at high w this discrepancy is reduced and at coolant movement rate about 350 cmVsec calculated Lcooi coincides with experimental. Heat transfer coefficient will be totally determined by coefficient of heat emission of cooling internal flow ai due to the fact that when Wa is increased the value of az is risen (because turbulence level of annular flow is increased). Thus, the equation (4.7) can be transformed with consideration of following conditions ... 

Rather different picture is observed under formation of hydrodynamic flows (coolant) structure in annular canals of tubular turbulent apparatus (Fig. 4.24). Flows structures in annular canals of cylindrical and divergent-convergent apparatus (Bo = 80) practically coincide up to volumetric flow of liquid flows Wa = 110 cmVsec. At Wa> 110 cmVsec in divergent-convergent apparatus reduction of criterion Bo is observed that is determined by the rise of longitudinal mixing rate (Fig. 4.25) and in cylindrical canal the rise of criterion Bo is observed (Fig. 4.24). 

Small-scale sodium experiments have been performed to investigate the coolant thermal-hydraulic behavior, such as turbulent mixing in compact reactor space, flow reversal by natural circulation with... 

The flow of the coolant around components and structures can cause structural vibrations due to the unsteady characteristics of the gas motion. The turbulence and the vortex shedding from an object protruding into the flow are the main sources of flow-induced vibrations that are considered. Flow-induced vibration analysis is done in two steps 1) determination of... 

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