Inner diameter turbulent flow

The minimum velocity requited to maintain fully developed turbulent flow, assumed to occur at Reynolds number (R ) of 8000, is inside a 16-mm inner diameter tube. The physical property contribution to the heat-transfer coefficient inside and outside the tubes are based on the following correlations (39) ... 

Noncircular Channels Calciilation of fric tional pressure drop in noncircular channels depends on whether the flow is laminar or tumu-lent, and on whether the channel is full or open. For turbulent flow in ducts running full, the hydraulic diameter shoiild be substituted for D in the friction factor and Reynolds number definitions, Eqs. (6-32) and (6-33). The hydraiilic diameter is defined as four times the channel cross-sectional area divided by the wetted perimeter. For example, the hydraiilic diameter for a circiilar pipe is = D, for an annulus of inner diameter d and outer diameter D, = D — d, for a rectangiilar duct of sides 7, h, Dij = ah/[2(a + h)].T ie hydraulic radius Rii is defined as one-fourth of the hydraiilic diameter. 

Hwang and Kim (2006) investigated the pressure drop in circular stainless steel smooth micro-tubes ks/d <0.1%) with inner diameters of 244 pm, 430 pm and 792 pm. The measurements showed that the onset of flow transition from laminar to turbulent motion occurs at the Reynolds number of slightly less than 2,000. It... 

Example 6 Losses with Fittings and Valves It is desired to calculate the liquid level in the vessel shown in Fig. 6-15 required to produce a discharge velocity of 2 m/s. The fluid is water at 20°C with p = 1,000 kg/m3 and ji = 0.001 Pa s, and the butterfly valve is at 0 = 10°. The pipe is 2-in Schedule 40, with an inner diameter of 0.0525 m. The pipe roughness is 0.046 mm. Assuming the flow is turbulent and taking the velocity profile factor a = 1, the engineering Bernoulli equation Eq. (6-16k written between surfaces 1 and 2, where the pressures are both atmospheric and the fluid velocities are 0 and V = 2 m/s, respectively, and there is no shaft work, simplifies to... 

Use the Reynolds analogy to derive an expression for the Nusselt number for fully developed turbulent flow in an annulus in which the inner wall is heated to a uniform temperature and the outer wall is adiabatic. Assume that the friction factor can be derived by introducing the hydraulic diameter concept. 

The piping inner diameter is typically designed for turbulent flow, Reynolds number greater than 2100, over the designed flow rate range. The units for performing this calculation are provided in the CCS system density (g/cm ), particle size (cm), velocity (cm/s) and viscosity (g/cms or poise). Note, the most common unit for viscosity is... 

Liquid methyl ethyl ketone (MEK) flows through a pipe with an inner diameter of 2.067 inches at an average velocity of 0.48 ft/s. At the fluid temperature of 20°C the density of liquid MEK is 0.805 g/cm and the viscosity is 0.43 centipoise [1 cP = 1.00 X 10" kg/(m s)]. Without using a calculator, determine whether the flow is laminar or turbulent. Show your calculations. 

For fully developed turbulent flow, the inner and outer convection coefficients are approximately equal to each other, and the tube annulus can be treated as a noncircular duct with a hydrauLc diameter of - 77, . The Nusselt num-... 

In a pioneering investigation, Serizawa [127, 128] measured the lateral void distribution as well as the turbulent axial liquid velocity fluctuations for bubbly air/water up-flows in a vertical pipe of diameter 60 (mm) inner diameter. They used electrical resistivity probes to measure the local void fraction, the bubble impaction rate, the bubble velocity and its spectrum. Turbulence quantities, such as the liquid phase mean velocity, and the axial turbulent fluctuations were measured using a hotfilm anemometer. A supplementary... 

It is generally accepted that the hydraulic diameter correlates Nu and /for fully developed turbulent flow in circular and noncircular ducts. This is true for the results accurate to within 15 percent for most noncircular ducts. Exceptions are for those having sharp-angled corners in the flow passage or concentric annuli with inner wall heating. In these cases, Nu and /could be lower than 15 percent compared to the circular tube values. Table 17.16 can be used for more accurate correlations of Nu and /for noncircular ducts. 

For turbulent flows, the entrance length is equivalent to 50 times the inner diameter. 

Equation (10) is valid for a column with an inner diameter of 100 mm and a clear liquid height greater than 1200 mm. In a further step we therefore examined, wether gas holdup is influenced by the column dimensions. In figure 3 gas holdup measurements are plotted versus gas linear velocity. The experiments were carried out in columns with inner dimensions larger than 150 mm and clear liquid heights higher than 1000 mm. Furthermore, the employed gas distributors caused a churn turbulent flow already at low gas throughputs. 

Now that we have required that the stagnation pressure be at the location Zmi, the question of just how far upstream of the nozzle entrance the pressure can be measured without loss of accuracy needs to be addressed. Using the deflnition of the Fanning friction factor to estimate the pressure drop for fully developed, turbulent flow (22), one can show that Po will increase by less than 0.10 bar as much as 100 inner tubing diameters upstream of the nozzle entrance as long as the flow speed inside the tubing does not markedly exceed 3 m/s (Figure 3 a). 

The unwanted deviation between Tmeas and Tavg can also be reduced if turbulent flow conditions are maintained upstream of the nozzle. [In fact, Halverson (24) reported that, under laminar flow conditions, the temperature measured with a thermocouple that touches the inner tubing wall can be closer to Tmeas than the one measured along the central axis of the flow.] To estimate the maximum tubing diameter that can be used upstream of the expansion device (i.e., while still maintaining turbulent flow), we proceed as follows The Reynolds number of the fluid at pre-expansion conditions under turbulent flow is given by... 

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