Pipes internal diameter , Reynolds

For pipe fittings, valves, and other flow obstructions the traditional method has been to use an equivalent pipe length Lequiv in Equation 4-30. The problem with this method is that the specified length is coupled to the friction factor. An improved approach is to use the 2-K method,s-6 which uses the actual flow path length in Equation 4-30 — equivalent lengths are not used — and provides a more detailed approach for pipe fittings, inlets, and outlets. The 2-K method defines the excess head loss in terms of two constants, the Reynolds number and the pipe internal diameter ... 

Table 48.2 Effect on Reynolds Numbers of Changing Pipe Internal Diameter for a Fixed Volumetric Flow Rate at Ambient Conditions...

Derive an expression relating the pressure drop for the turbulent flow of a fluid in a pipe to the heat transfer coefficient at the walls on the basis of the simple Reynolds analogy. Indicate the assumptions which are made and the conditions under which you would expect it to apply closely. Air at 320 K and atmospheric pressure is flowing through a smooth pipe of 50 mm internal diameter, and the pressure drop over a 4 m length is found to be 150 mm water gauge. By how much would you expect the air temperature to fall over the first metre if the. wall temperature there is 290 K ... 

Here, IDin is the internal diameter (in inches) of the pipe that contains the fitting. This method is valid over a much wider range of Reynolds numbers than the other methods. However, the effect of pipe size (e.g., 1 /IDin) in Eq. (7-37) does not accurately refect observations, as discussed below. 

Measurements with different fluids, in pipes of various diameters, have shown that for Newtonian fluids the transition from laminar to turbulent flow takes place at a critical value of the quantity pudjp in which u is the volumetric average velocity of the fluid, dt is the internal diameter of the pipe, and p and p. are the fluid s density and viscosity respectively. This quantity is known as the Reynolds number Re after Osborne Reynolds who made his celebrated flow visualization experiments in 1883 ... 

The Reynolds number characterizing laminar-turbulent transition for bulk flow in a pipe is about Re 2300 provided that the fluid moves unidirectionally, the pipe walls are even and behave in a hydraulically smooth manner, and the internal diameter remains constant. However, intestinal walls do not fulfill these hydraulic criteria due to the presence of curvatures, villi, and folds of mucous membrane, which are up to 8 mm in the duodenum, for instance (Fig. 18). Furthermore, the internal diameter of the small intestine is estimated to... 

To use the Pipe Friction Manual chart, compute the velocity of the liquid in the pipe by converting the flow rate to cubic feet per second. Since there are 42 gal/bbl and 1 gal = 0.13368 ft3, 1 bbl = (42)(0.13368) = 5.6 ft3. With a flow rate of 500 bbl/h, the equivalent flow in ft3 = (500)(5.6) = 2800 ft3/h, or 2800/3600 s/h = 0.778 ft3/s. Since 6-in schedule 40 pipe has a cross-sectional area of 0.2006 ft2 internally, the liquid velocity, in ft/s, equals 0.778/0.2006 = 3.88 ft/s. Then, the product (velocity, ft/s)(internal diameter, in) = (3.88)(6.065) = 23.75. In the Pipe Friction Manual, project horizontally from the kerosene specific-gravity curve to the vd product of 23.75 and read the Reynolds number as 61,900, as before. In general, the Reynolds number can be found faster by computing it using the appropriate relation given in Table 6.1, unless the flow velocity is already known. 

Re = Reynolds number, a dimensionless quantity ID = Internal diameter of the pipe, ft y = Linear velocity of the fluid at flowing temperature and pressure, ft/s... 

Although there are many designs of flow nozzles, the International Standards Association (ISA) nozzle has become an accepted standard form in many countries. Values of K for various diameter ratios of the ISA nozzle are shown in Fig. 10.8 as a function of Reynolds number. Note that in this case the Reynolds number is computed for the approach pipe rather than for the nozzle throat, which is a convenience as Nr in the pipe is frequently needed for other computations also. 

K = value of at a Reynolds number of 1 K = value of Kat high Reynolds numbers = internal pipe diameter in inches. 

Numbers are a fundamental component of measurements and of the physical properties of materials. However, numbers without units are meaningless. Few quantities do not have units, e.g., specific gravity of a substance is the ratio of the mass of a substance to the mass of an equal volume of water at 4°C. Another unitless quantity is the Reynolds Number, Re = pvllr where p is the density v is the velocity rj is the viscosity of the fluid, and / is the length or diameter of a body or internal breadth of a pipe. The ratio r]lp = /i the kinematic viscosity with units of fit. R = vHp and has no units if the units of v, I, and p are consistent. 

Reynolds number A measure of how turbuient a flow is. it s the linear velocity, times density, times internal pipe diameter, divided by viscosity. 

This workbook computes the Nusselt number for forced convection in a circular pipe as a function of the Reynolds (based on diameter) and Prandtl numbers (and where appropriate one or two other parameters). It includes subroutines for laminar, transition, and turbulent flows and for liquid metals. Results for a range of Reynolds and Prandtl numbers are shown in this plot. This spreadsheet was developed to aid in verifying our internal-flow module (Ribando, 1998). 

Moody plot, chart, diagram A dimensionless representation of friction factor with Reynolds number tor a fluid flowing in a pipe. Presented on log-log scales, the diagram includes laminar, transition, and turbulent flow regimes. It also includes the effects of pipe relative roughness as a dimensionless ratio of absolute roughness with internal pipe diameter. The plot was developed in 1942 by American engineer and professor of hydraulics at Princeton, Louis Ferry Moody (1880-1953). 

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