Number of pipe diameters

A tabulated form as in Table 19.3. This shows flows versus pipe length and diameter for both copper and steel. Such tables are included in British Gas lM/16 and British Standard BS 6891. Note that Table 19.3 includes allowances for elbows, tees and bends. Allowances, equivalent to numbers of pipe diameters, must be made for all pipe fittings, which cause an additional pressure loss. Further details for allowances to be made for pipefittings, including valves and nonreturn valves, are given in Table 19.4. 

Number of pipe diameters Number of velocity heads (u2/2g)... 

Fitting n, number of pipe diameters K, number of velocity heads... 

From Eq. 6.26 we see that this is the number of pipe diameters needed to have the same friction loss as the fittings. Thus, the equivalent length is 1085[(3.068/ 12) ft] = 277 ft. Therefore, the adjusted length of the pipe is... 

When the gas distribution network was planned, the number of pipe diameters was rationalised. For each pipe diameter, joints and couplings need to be made. Ideally, the pipe diameter should suit the planned flow, but a large number of pipe diameters increases the costs of manufacture and of stocks. Typical pipe dimensions are given in Table 14.3. 

As a vessel is loaded, it moves downward because of deflection of the load cells and support stmcture. Pipes rigidly attached to a vessel restrict its free movement and assume some portion of the load that cannot be measured by the load cells. This is very detrimental to scale accuracy. Deflection of the load cell is unavoidable deflection of the vessel support stmcture should be minimized. Anything which increases vessel deflection, eg, mbber pads used for shock protection, must be avoided. The total number of pipes should be minimized and be of the smallest diameter, thinnest wall possible. Pipe mns to weigh vessels must be horizontal and the first pipe support should be as far as possible from the vessel. Alternatively, a section of mbber hose or flexible bellows should be used to make the final connection to the vessel. The scale should be caUbrated using weights, not by means of an electrical simulation method, which cannot account for the effects of the piping or test the correct functioning of the scale. 

Pipe-type electrostatic precipitators are used to collect liquid aerosols (e.g., mists and fogs). They are also used in applications which require water flushing of collection electrodes. The diameter of precipitator pipes is typically in the range of 15 0 cm, and the length is in the range of 3-6 m. The number of pipes depends on the total gas flow. The gas-flow rates in pipe-type electro static precipitators is normally much lower than in duct-type precipitators. 

For coils, the critical Reynolds number is a function of the ratio of pipe diameter to coil diameter, computed as follows ... 

The equation relating the volumetric flow rate to pressure drop is similar to that for the orifice. The only difference is that the coefficient Co is replaced by the Venturi coefficient, Cv This coefficient approaches 0.99 in. large pipes at high Reynolds numbers. Figure 6.7 illustrates the variation of C as a function of pipe diameter and Reynolds number at the throat. 

It is usually used in order to produce large numbers of medium diameter tanks, or long runs of medium pressure (up to 15 bar) specification pipe. An example of a company currently associated with this process is Owens Corning Pipe. 

Pushkin and Sorokin (1969) studied flooding in a wide range of vertical pipes having diameter range from 6 to 309 mm. They provided with a flooding correlation using Kutateladze number which is independent of pipe diameter as... 

Figure 10.27 Effect of an expansion on local mass transport rate the dimensionless mass transport coefficient ki lki Q is plotted as a function of the dimensionless distance from the expansion x/Dq. Here q is the mass transport coefficient far away from the expansion and Dq is the pipe diameter down stream from the expansion. Reynolds number (o) 2.1 x 10 ( ) 4.2 X 10, ( ) 8.4 X 10 and (+ ) 13 X 10. Ratio of pipe diameters = 0.625, adapted...

Thus plotting IIi as a function of 112, the Reynolds number, produces smooth curves with parametric lines described by 113/2, which is shown in Fig. 4.1. Fig. 4.1 shows Hi as a function of Reynolds number for a variety of spherical particles in a number of different diameter pipes. d(s) identifies sphere diameter. The curves are distinguished by the parametric 113/2, which is LchJD. Fig. 4.1 shows that IIi collapses to a common horizontal line in the turbulent flow regime, that is, at high Reynolds numbers. This horizontal line corresponds to the Burke—Plummer result. For low Reynolds numbers, the correlation for each size sphere is negatively sloped, which corresponds to the Blake—Kozeny result. However, unlike the Ergun equation, the different sized spheres each produce a different correlation in the laminar flow... 

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

At the same time the top-suspended reactor has the complication of accommodating the thermal displacement of the primary coolant pressure pipes relative to the sodium pumps, taking into account the large temperature difference between the "cold" upper support slab (60 C) and the relatively "hot" (approx. 400 C) sodium pipes. To solve this it is necessary to use longer sodium pipes, or a greater number of small diameter pipes, or as a last resort to introduce movable items into the sodium pipes. Changing to the top-suspension design... 

Designs with increased number of pipes with reduced diameters have shown apparent advantages. Apart from bringing down the loss of core flow, it is possible to go for seamless pipes with reduced thickness, by which the structural reliability can be improved significantly. However, a general feeling has been expressed that increased number of pipes may decrease the structural reliability due to the overall increase of the pipe lengths. The incorporation of a flow diode device to increase the friction drop for break flow may also help to increase the core flow. 

A greater number of pipes with reduced diameters have definite advantages. For the smaller diameter pipes, a lesser wall thickness can be chosen without increase of stress. As a result of this, the pipe become relatively flexible, which can accommodate higher thermal expansions. 

Table 1 provides an idea about the diameter and flow velocities with the increased number of pipes, for a typical 500 MWe FBR (PFBR) which has four pipes in the reference design with two primary pumps. 

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