Velocity water-flow

Correlations for CHF in refrigerants Weisman and Pei (1983) suggested a theoretically based predictive procedure for CHF at high-velocity water flow in both uniformly and nonuniformly heated tubes, which was found to yield equally good results with experimental data for four other fluids R-l 1, R-113, liquid nitrogen, and anhydrous ammonia. 

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. 

Using a water eductor to wet the polymer particles rapidly. The polymer is fed into a water-jet eductor, where high-velocity water flow instantly wets each particle, thus preventing lumping. This procedure speeds solution preparation and is particularly useful where large volumes of solutions are required. 

A distributor is frequently installed at the top of the column for use during backwash. It collects water evenly and prevents resin from escaping the column should unexpected surges develop in the water flow during backwash. Columns lacking an upper distributor or screen to prevent loss of resin should have an external system to prevent resin from being lost to the drain. It is referred to as a resin trap and may consist of a porous bag that fits over the outlet pipe or a tank designed to lower the linear velocity. Resin drops to the bottom of the tank and is returned to the column when convenient. 

Cooling Wa.ter. The primary rehabihty concern is that water chemistry must be maintained in a low fouling, noncorroding regime. In addition, water flow velocity must be maintained above a certain threshold (ca 0.5 m/s in tubeside flow) to avoid fouling and corrosion. 

Unhke other refrigeration systems, the chiUed-water flow rate is of no particular importance in steam-jet system design, because there is, due to direct heat exchange, no influence of evaporator tube velocities and related temperature differences on heat-transfer rates. Widely varying return chiUed-water temperatures have Uttle effect on steam-jet equipment. 

Water flow, gal/min Spray-nozzle pressure, Ih/im Water flow per nozzle, gal/min Effective area, length X width, fd Effective height, ft Wind velocity, ft/min... 

Impediments to water flow resulting from inadequate equipment design or lodgement of foreign objects in the tubes can exercise a dramatic effect on the erosion-corrosion process. Much of this influence is linked to the creation of turbulence and the simple increase in fluid velocity past obstructions. The importance of these factors is quickly recognized when the phenomenon of threshold velocity is considered. 

A common cause of erosion is partial obstruction of tubes by foreign bodies. At the inlet end, for example, debris such as sticks, glass fragments, and wood chips may lodge in tube ends or be held against the tubes by water flow. The nominal velocity of the water past the obstruction increases according to the degree of obstruction. It can be shown... 

Cathodic protection of water power turbines is characterized by wide variations in protection current requirements. This is due to the operating conditions (flow velocity, water level) and in the case of the Werra River, the salt content. For this reason potential-controlled rectifiers must be used. This is also necessary to avoid overprotection and thereby damage to the coating (see Sections 5.2.1.4 and 5.2.1.5 as well as Refs. 4 and 5). Safety measures must be addressed for the reasons stated in Section 20.1.5. Notices were fixed to the turbine and the external access to the box headers which warned of the danger of explosion from hydrogen and included the regulations for the avoidance of accidents (see Ref. 4). 

Heat transfer coefficient between a pipe and a wall. Water flows in a pipe d =15 mm) with a velocity of v = 1.0 m s. The mean temperature of water is 0 , = 15 °C, and the wall temperature 6 = 50 °C. Calculate the heat transfer coefficient away from the pipe inlet. For water the properties are... 

Warm and hot water heating systems 27/453 Design water flow temperature 27/454 Maximum water velocity 27/454 Minimum water velocity 27/454 System temperature drop 27/455 Use of temperature-limiting valves on emitters 27/455... 

With respect to general corrosion, once a surface film is formed the rate of corrosion is essentially determined by the ionic concentration gradient across the film. Consequently the corrosion rate tends to be independent of water flow rate across the corroding surface. However, under impingement conditions where the surface film is unable to form or is removed due to the shear stress created by the flow, the corrosion rate is theoretically velocity (10 dependent and is proportional to the power for laminar flow and... 

In sea-water flowing at slower velocities and more especially in stagnant conditions, pitting and crevice corrosion may develop, particularly beneath deposits and marine growths at the surface of the metal. Some data for the Ni-30 Cu Alloy 400 are shown in Fig. 4.40 the corrosion was mostly pitting. 

The specimens should be oriented so that their flat surfaces are parallel to the direction of water flow and so that one specimen will neither shield an adjacent specimen from effects of water velocity nor create any considerable extra turbulence upstream of it. 

Sudden eniargement/contraction, 70, 80 Total line, 64 Two-phase flow, 124-127 Vacuum lines, 128-134 Velocities, 83, 89, 90 Velocities, chart, 91 Velocity head, 71 Water flow calculations, 96 Water flow, table, 93, 97, 98 Pressure level relationships,... 

Fig. 27. Approximate boundary of the low-velocity burn-out regime for water flowing in round tubes. The low-velocity regime lies to the left of any given curve [from Macbeth (M2)].

Water flows from a tap at a pressure of 250 kN/m2 above atmospheric. What is the velocity of the jet if frictional effects are neglected ... 

Water flows in a 50 mm pipe, 100 m long, whose roughness e is equal to 0.013 mm. If the pressure drop across this length of pipe is not to exceed 50 kN/m2, what is the maximum allowable water velocity The density and viscosity of water may be taken as 1000 kg/m3 and 1.0 mN s/m2 respectively. 

Water flows at a velocity of 1 m/s over a plane surface 0.6 m wide and 1 m long. Calculate the total drag force acting on the surface if the transition from streamline to turbulent flow in the boundary layer occurs when the Reynolds group ReXc = 105. 

Water flows at 2 m/s through a 2.5 m length of a 25 mm diameter tube. If the tube is at 320 K and the water enters and leaves at 293 and 295 K respectively, what is the value of the heat transfer coeflicienl How would the outlet temperature change if the velocity were increased by 50% ... 

Maynes and Webb (2002) presented pressure drop, velocity and rms profile data for water flowing in a tube 0.705 mm in diameter, in the range of Re = 500-5,000. The velocity distribution in the cross-section of the tube was obtained using the molecular tagging velocimetry technique. The profiles for Re = 550,700,1,240, and 1,600 showed excellent agreement with laminar flow theory, as presented in Fig. 3.2. The profiles showed transitional behavior at Re > 2,100. In the range Re = 550-2,100 the Poiseuille number was Po = 64. 

Hao et al. (2007) investigated the water flow in a glass tube with diameter of 230 Lim using micro particle velocimetry. The streamwise and mean velocity profile and turbulence intensities were measured at Reynolds number ranging from 1,540 to 2,960. Experimental results indicate that the transition from laminar to turbulent flow occurs at Re = 1,700—1,900 and the turbulence becomes fully developed at Re > 2,500. 

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