Straight tubing

At Che opposite limit, where Che density Is high enough for mean free paths to be short con ared with pore diameters, the problem can be treated by continuum mechanics. In the simplest ease of a straight tube of circular cross-section, the fluid velocity field can easily be obtained by Integrating Che Nsvler-Stokes equations If an appropriate boundary condition at Che... 

Coils For flow inside helical coils, Reynolds number above 10,000, multiply the value of the film coefficient obtained from the apphcable equation for straight tubes by the term (1 + 3..5 D /DJ. 

Readings given by open straight tubes (Fig. 10-ld and le are too low due to flow separation. Readings of closed tubes oriented perpendicularly to the axis of the stream and provided with side openings (Fig. 10-lg) may be low by as much as two velocity heads. 

Venturi Meters The standard Herschel-type venturi meter consists of a short length of straight tubing connected at either end to the pipe line by conic sections (see Fig. 10-15). Recommended proportions (ASME PTC, op. cit., p. 17) are entrance cone angle Oti = 21 2°, exit cone angle Cto = 5 to 15°, throat length = one throat diameter, and upstream tap located 0.25 to 0.5 pipe diameter upstream of the entrance cone. The straight and conical sections should be joined by smooth cui ved surfaces for best results. 

Tube-Bundle Bypassing Shell-side heat-transfer rates are maximized when bypassing of the tube bundle is at a minimum. The most significant bypass stream is generally between the outer tube limit and the inside of the shell. The clearance between tubes and shell is at a minimum for fixed-tube-sheet construc tion and is greatest for straight-tube removable bundles. 

Relatively low cost in small-capacity straight-tube type... 

Straight tube loss See Chapter 1, Fluid Flow, Piping Pressure Drop ... 

All losses except for straight tube Straight tube loss 2- Ah = 2.9-4-N 2g See Chapter 1, Fluid Flow, Piping Pressure Drop ... 

Equation (12) indicates that the band variance is directly proportional to the square of the tube radius, very similar to that for a straight tube. At high linear velocities, Tijssen deduced that... 

The fixed-tubesheet exchanger is the most common, and generally has the lowest capital cost per ft of heat-transfer surface area. Fixed-tubesheet exchangers consist of a series of straight tubes sealed between flat, perforated metal tubesheets. 

As with other removable-bundle exchangers, the inside of the shell, and to the outside of the tubes. However, unlike the straight-tube exchanger, whose tube internals can be mechanically cleaned, there is no way to physically access the U-bend region inside each tube, so chemical methods are required for tubeside maintenance. 

Poiseuille flow Parabolic laminar flow in a straight tube. 

The simplest model ignores tortuosity and assumes the bed equivalent hydro-dynamieally to a matrix of straight tubes - like a bundle of drinking straws e.g. as in Figure 2.10. 

Fig. 4. Singularities in MWCNT imaged by means of basal plane lattice fringes, (a) Straight ideal MWCNT. (b) Capped MWCNT. The tube closes progressively by clusters of 2-5 graphene layers. (c)(d) Bamboo-like compartments in straight tubes.

Maximum Unsupported Straight Tube Spans (AH Dimensions in In.)... 

Liquids in turbulent flow in circular helical coils should be handled the same as for gases or use 1.2 Xhj for straight tubes. 

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