Velocity head formula

When vapor bubbles eollapse inside the pump the liquid strikes the metal parts at the speed of sound. This is the elicking and popping noise we hear from outside the pump when we say that eavitation sounds like pumping marbles and roeks. Sound travels at 4,800 ft per second in water. The velocity head formula gives a elose approximation of the energy contained in an imploding cavitation bubble. Remember that implosion is an explosion in the opposite direction. 

The term pump head represents the net work performed on the liquid by the pump. It is eomposed of four parts. They are the statie head (Hs), or elevation the pre.ssure head (Hp) or the pre.ssures to be overcome the friction head (Hf) and velocity head (Hf), which are frictions and other resistances in the piping system. These heads are discussed in Chapter 8. The head formula is the following ... 

Hv - the velocity head, or the energy lost into the. system due to the velocity of the liquid moving through the pipes. The formula is ... 

In the velocity head method of accounting for fitting losses, a multiplicative coefficient is found empirically by which the velocity head term (v)2/2g is multiplied to obtain the fitting loss. This term is then added to the regular velocity head losses in Eq. (63). Extensive tables and charts of both equivalent lengths and loss coefficients and formulas for the effect of flow rate on loss coefficients... 

The coefficient of local resistance to the unit area with sudden expansion is calculated (in the calculation of the velocity head speed in a smaller cross section) by the formula (l-Sj/S (Fig. 13.1), and cylindrical por-... 

Alkylation of cyclohexane with isoprene can be carried out with alkyl radicals formed at 450°C and 20.3 MPa (200 atm) (73). 40% Pentenylcyclohexanes, 20% dipentenes (ie, substances having the general formula C qH ), and 40% higher boiling compounds are obtained using a 6.8 molar ratio of cyclohexane to isoprene and a space velocity of 2.5. Of the pentenylcyclohexanes, the head and tail products are in equal amounts. Even... 

Detonation Velocity, Influence of Inert Components and Inert Additives. Cook (Ref 1, p 211), under the heading Influence of Inert Additives on the Detonation Velocity of Ideal Explosives , gives a formula for determination of detonation velocity of an explosive contg an inert additive if velocity of pure expl is known. 

For a suppressed weir with velocity of approach considered, he used the same value for Cd in Eq. (10.73). The Francis formulas have been checked by many others and found to be accurate within 1 to 3% for all heads above 0.3 ft but to be about 1% too low for heads of 0.1 ft and under. 

This equation was obtained by fitting a curve to the plotted values of Cd for a great many experiments and is purely empirical. Capillarity is accounted for by the second term, while velocity of approach (assumed to be uniform) is responsible for the last term. Rehbock s formula has been found to be accurate within 0.5% for values of Z of 0.33 to 3.3 ft and for values of H of 0.08 to 2.0 ft with the ratio H/Z not greater than 1.0. It is even valid for greater ratios than 1.0 if the bottom of the discharge channel is lower than that of the approach channel, so that backwater does not affect the head. 

Problems involving head loss for thick suspensions of fine materials at velocities greater than calculated by Eq (18-30)—that is, for flow in the turbulent region—can be solved by the usual friction charts or formulas developed for the flow of water, after making due corrections for the density of the suspension. 

Compute the friction-head loss using the Hazen-WiUiams formula. The Hazen-Williams formula is hf = (u/1.318C/ ° 63) 85, where h j = friction-head loss per foot of pipe, in feet of water v = water velocity, in ft/s C = a constant depending on the condition and kind of pipe and Rh = hydraulic radius of pipe, in ft. 

Head loss calculations for bed adsorption are therefore the same as those with filtration. Since head loss formulas through beds of solids have already been discussed under filtration, they will not be pursued here. The important point to remember is that for filtration formulas to apply under moving-bed adsorption operations, the superficial velocity should now be considered relative velocity. 

It shown that the total flow can be calculate by the formula of weir width B, weir head H and water depth of flume d, and the value of g is relate to Hid, but the flow coefficient Q and the non-uniform velocity coefficient a must be obtained by experiment. 

In weir flow calculation formula, the flow coefficient is relate to the weir flow shrinkage and head loss for local resistance non-uniform velocity coefficient a is relate to the inhomogeneous degree of approach velocity in flume cross section and the ratio of weir head H and weir height P. Therefore, the value or expression of and a are not identical by test in specific conditions and certain circumstances at home and abroad. 

As shown from Table 1, in Francis formula, the approach velocity is not considered, which will cause obviously calculated flow errors, and the flow value is very close as calculate by the formula of Rehbock and this article. In fact, if the sectional velocity distribution of weir head under different HIP can be accurate measured, the value tzcan be determined, and the flow rate can be precise calculated by Equation (9), when for preliminary calculation can also use Equation (12). 

RECOMMENDATION Growth studies should include precise and reliable measurements of weight and length velocity and head circumference. Duration of measurements should cover at least the period when infant formula remains the sole source of nutrients in the infant diet. Appropriate measures of body composition also require assessment. 

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