Sudden enlargement

The integration in equation (3.92) can be carried out after insertion of the velocity profiles for the appropriate viscosity model to obtain the pressure loss (p2 - pf)- For power-law fluids, this procediue leads to  

For a horizontal system, zi = Z3, putting pi P2 and substituting for a from equation (3.16), equations (3.93) and (3.94) yield the following expression for the head loss, hg  

If n were equal to zero, the velocity would be uniform across the pipe cross-section (a = 1) and equation (3.95) would reduce to 

This agrees with the expression for turbulent Newtonian flow when the veloeity profile is assiuned to be approximately flat. 

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FIG. 6-13 Contractions and enlargements (a) sudden contraction, (h) rounded contraction, (c) sudden enlargement, and (d) uniformly diverging duct. 

Expansion and Exit Losses For ducts of any cross section, the frictional loss for a sudden enlargement (Fig. 6-13c) with turbulent flow is given by the Borda-Carnot equation ... 

There is a sudden reduction in the suction between the tank and the piping. There is an eccentric 6-to-4 reducer between the suction pipe and the pump. There is a eoneentrie 3-to-4 inereascr from the pump back into the piping, and a sudden enlargement going into the discharge tank. The formula is ... 

This calculation includes the contribution from the elbow and the sudden enlargement. 

USED AS INCREASER LOSS IS UP TO 40% MORE THAN THAT CAUSED BY A SUDDEN ENLARGEMENT... 

For sudden enlargements in a pipe system when there is an abrupt change from a smaller pipe flowing into a larger pipe, the resistance coefficient, K, is given by ... 

For higher resistance valves, such as globes and angles, the losses are less than sudden enlargements or contractions situations. For these reduced seat valves the resistance coefficient EL, can be calculated as [3] ... 

Note that for straight duct flow at constant cross-section, the total and static pressures decrease together (constant resistance). At the contraction section, the total pressure decreases very litde, but static pressure is converted to velocity pressure, because static and velocity pressures are mutually convertible. At the sudden enlargement, the process of changing the velocity pressure to static pressure is inefficient, and a total pressure loss occurs. AtJ the static pressure is 0, and the total pressure is the velocity pressure as the gas stream leaves the duct. 

Venting, dusts, (deflagration), nomograph, API, 514-520 Relief valves, 400 Code requirements, 415, 420 Installation, 422, 429-434 Safety-relief, 400 Relieving pressure, 411-417 Resistance coefficient, K, (flow), 71, 72 Flow coefficient, Q, 81, 83 Pipe sizing, 83, 84, 86 Sudden contraction, 80 Sudden enlargement, 80 Tables/charts, 73-76, 77, 78-80 Valves, 81... 

Friction losses occurring as a result of a sudden enlargement or contraction in the cross-section of the pipe, and the resistance of various standard pipe fittings, are now considered. 

Water flows at 7.2 m- /h through a sudden enlargement from a 40 mm to a 50 mm diameter pipe. What is the loss in head ... 

For flow at right angles to the axes of the tubes, the cross-sectional area is continually changing, and the problem may be treated as one involving a series of sudden enlargements and sudden contractions. Thus the friction loss would be expected to be directly proportional to the number of banks of pipes j in the direction of flow and to the kinetic energy of the fluid. The pressure drop - APf may be written as ... 

Braga M, Ringel MD, Cooper DS. Sudden enlargement of local recurrent thyroid tumor after recombinant human TSH administration. J Clin Endocrinol Metab 2001 86(11) 5148-51. 

Hepatic venous thrombosis, also known as Budd-Chiari syndrome, is caused by hypercoagulable disorders precipitated by pregnancy, infection, and birth control medication. An acute painful abdomen, sudden enlargement of the liver, and the presence of ascites make up a triad of clinical symptoms that are important in the diagnosis of this syndrome. Myeloproliferative disorders such as polycythemia vera and paroxysmal nocturnal dyspnea were previously thought to be responsible. Factor V Leiden and prothrombin 20210 mutations are also known to be responsible, Other intraabdominal thromboses include portal vein thrombosis, mesenteric vein thrombosis and renal vein thrombosis. 

Fc = friction due to sudden contraction, ft 1 lbf/lbm Fe = friction due to sudden enlargement, ft lbf/lbm Fe = correction factor for radiant heat transfer based on emissivities and absorptivities of surfaces, dimensionless defined by Eqs. (6) and (7)... 

Note For sudden enlargements or sudden contractions, use the smaller diameter on the nominal pipe size scale. 

The entrance loss he, in feet, assuming a basket-type strainer is used at the suction-pipe inlet, is Kv2/(2g), where K = a constant from Fig. 6.14 v = liquid velocity, in ft/s and g = 32.2 ft/s2. The exit loss occurs when the liquid passes through a sudden enlargement, as from a pipe to a tank. Where the area of the tank is large, causing a final velocity that is zero, hex = v2/lg. 

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