Pressure drop, calculation

In pipe distributors, the pressure drop requited for good gas distribution is 30% of the bed pressure drop for upward facing holes, but only 10% for downward facing ones. The pressure drop calculation and the recommended hole density are the same as for a perforated plate. To maintain good gas distribution within the header system, it is recommended the relation... 

Total pressure drop for vertical upflow of gases and solids includes acceleration and fric tional affec ts also found in horizontal flow, plus potential energy or hydrostatic effects. Govier and Aziz review many of the pressure drop calculation methods and provide recommendations for their use. See also Yang AIChE J., 24, 548-552 [1978]). 

Frictional Pressure Drop Usually this does not have a significant effect on the reaclor size, except perhaps when the flow is two-phase. Some approximate relations fbe cited that are adequate for pressure-drop calculations of homogeneous flow reactions in pipelines. The pressure drop is given by... 

FIG. 14-32 Aeration factor for pressure drop calculation, sieve plates. [Bolles and Fair, Encyclopedia of Chemical Processing and Design, vols. 16, 86. J. M. McKetta (ed.), Marcel Dekker, New Yoik, J9S2.]... 

This relationship holds for a Reynolds number range of 2,100 to 10 . For smooth tubes (assumed for heat exchanger tubeside pressure drop calculations), a constant of 23,000 should be used instead of 20,000. 

The velocities are suggestive only and are to be used to approximate line size as a starting point for pressure drop calculations. 

Pressure drop calculations for shnple geometries like pipe flows are straightforward. The Farming friction factor is given by ... 

The equivalent length of the main flare header is then calculated from the flare stack to the last safety valve, taking into consideration the straight length of the pipe and approximate equivalent lengths for bends, etc. If the achial location of the flare stack is not known by that time, it maybe assumed to be 500 ft from the last piece of equipment. Later on, even if it varies from 500 ft, it will not affect the pressure drop calculation at all compared with the entire length of the pipe. 

TWO-PHASE PRESSURE DROP CALCULATION IN A PIPE LINE PIPE INTERNAL DIAMETER, inch 3.070... 

A slit die is designed on the assumption that the material is Newtonian, using apparent viscous properties derived from capillary rheometer measurements, at a particular wall shear stress, to calculate the volumetric flow rate through the slit for the same wall shear stress. Using the correction factors already derived, obtain an expression for the error involved in this procedure due to the melt being non-Newtonian. Also obtain an expression for the error in pressure drop calculated on the same basis. What is the magnitude of the error in each case for a typical power law index n = 0.377... 

Pressure drop through line systems containing more than one pipe size can be determined by (a) calculating the pressure drop separately for each section at assumed flows, or (b) determining the R totals iox each pipe size sep>-arately, and then converting to one selected. size and using that for pressure drop calculations. For example, using... 

For a system of multiple components of valves, pipe, and fittings. Equation 2-25 can be used to establish a component size to which each separate resistance can be expressed as a common denominator, or common pipe size. Under these conditions, the corrected Rvalues are additive and can be used as one number in Equation 2-27. These types of corrections should be made to improve and more accurately represent the pressure drop calculations. 

For estimating purposes in usual piping systems, the values of pressure drop across an orifice or nozzle will range from 2 to 5 psi. For more exact system pressure drop calculations, the loss across these devices should be calculated using some size assumptions. 

If sonic velocity of step 2 is greater than calculated velocity of step 1, calculate line pressure drop using usual flow equations. If these velocities are equal, then the pressure drop calculated will be the maximum for the line, using usual flow equations. If sonic velocity is less than the velocity of step 1, reassume line size and repeat calculations. 

For non-critical flow the maximum back pressure must be set and pressure drop calculated by the usual friction equations. 

Determine the percent hole area in the active tray portion for pressure drop calculation. Note that hole size does not have to be set at this point (Figure 8-143.)... 

For pass corrections use fluid flow expansion and contraction as an illustration of one approach to these pressure drop calculations. 

Reboiler piping at the liquid inlet and at the vapor outlet can be summarized for convenience in pressure drop calculations into the suggested equivalent feet of Table 10-32. The inlet assumes piping to conveniently pipe the reboiler to a distillation column using welded fittings and a full open gate... 

Figure 10-155. Shell-side friction factor, f , for pressure drop calculation is determined from plot vs. Reynolds Number, z = viscosity at average flowing temperature, centipoise. (Used by permission Brown Fintube Co., A Koch Engineering Company, Houston, Texas.)...

Beattie DRH, Whalley PB (1982) A simple two-phase flow frictional pressure drop calculation method. Int J Multiphase Flow 8 83-87... 

The line pressure-drop calculation is set out on the calculation sheet shown in Table 5.4. Pump selection ... 

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