Piping pressure drop

A handy relationship for turbulent flow in eommercial steel pipes is  

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. 

Branan, Carl R. Estimating Pressure Drop, Chemical Engineering, August 28, 1978. 

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Piping pressure drop Optimum pressure drop... 

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 ... 

Usually used where piping pressure drop is high and therefore natural circulation is impractical. 

When the predetermined system blowdown pressure is reached, the pilot valve closes, full system pressure is restored to the dome above the piston, and the piston is quickly moved to the closed position. The pilot valve pressure sensing point may be located in the main valve inlet neck, or on the shell of the vessel being protected. The valve is less affected by inlet piping pressure drop in the latter case, as described below. 

Multiply K by the empty-pipe pressure drop to obtain the pressure drop eaused by the Kenies mixer model installation. The theoretieal horsepower required by the Kenies mixer is determined by... 

Quite often the mixing units or elements are installed in a circular pipe however, they can he adapted to rectangular or other arrangements. Pressure drop through the units varies depending on design and whether flow is laminar or turbulent. Because of the special data required, pressure drops should he determined with the assistance of the manufacturer. Of course, pressure drops must he expected to he several multiples of conventional pipe pressure drop. 

For two stages of compression, what should be the pressures across the cylinders if the intercooler and piping pressure drop is 3 psi ... 

The equations in the section Piping Pressure Drop are, of course, intended for use with full pipes. Reference 12 provides a rapid way to estimate whether a horizontal pipe carrying liquid is full. The criteria are... 

It should be noted that Equations 13.9 and 13.10 apply to smooth pipes, whereas the pipes used for transmission of fluids usually have some surface roughness, which increases the friction factor. However, for short fluid transmission pipes, the overall pressure drop is usually dominated by the pressure drop in the pipe fittings (valves, bends, etc). Thus, for short transmission pipes, there is little point in calculating the straight pipe pressure drop accurately. If the transmission pipe is long (>100 m) and straight, then the Fanning friction factor can be correlated as7 ... 

ISO 4059 1978 Polyethylene (PE) pipes - Pressure drop in mechanical pipe-jointing systems - Method of test and requirements ISO 4427 1996 Polyethylene (PE) pipes for water supply - Specifications ISO 4437 1997 Buried polyethylene (PE) pipes for the supply of gaseous fuels - Metric series - Specifications... 

In motionless mixers the energy input for mixing is provided by the pressure loss from the mean flow. All manufacturers can provide pressure drop data. These are usually given as a friction factor or as a multiplier for the empty-pipe pressure drop. Values range from 30 to 1000 times the empty-pipe friction factor. 

While this is the general recommendation, compliance with this is not always possible. As seen earlier in this book, higher oudet pressure drops may result in reduced valve capacity and instability. In that case, other types of SRVs as discussed in Chapter 9 need to be taken into consideration. API RP 521 also states the outlet pressure drop for individual relief valves should be based on the actual rated valve capacity consistent with the inlet piping pressure drop as discussed in Section 6.1. 

Having now established the friction factor f for the general pressure drop equation, the dimensional analysis equation for pipe pressure drop can be derived. A simple equation is now derived from the earlier Bernoulli equation ... 

Once the two-phase flow modulus (YG) for the particular flow regime has been calculated, Equation 3-60 can be used to calculate APT/100ft, the two-phase, straight-pipe pressure drop. The pressure drop of liquid or gas flowing alone in a straight pipe can be expressed as ... 

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