Pressure reducing orifice plates

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SUMMARY

This discussion focuses on calculating flowrate and pressure drop across two pressure reducing orifice plates in series, specifically for seawater applications. The initial supply pressure is 9 bar, with the goal of estimating flowrates at reduced pressures of 6, 4, and 2 bar. Key considerations include the orifice plate dimensions, the minimum flow required for the oil cooler, and the impact of choked flow conditions. The iterative nature of the calculations is emphasized, as pressure drop is dependent on velocity and Reynolds number.

PREREQUISITES
  • Understanding of pressure reducing orifice plate design
  • Knowledge of fluid dynamics, particularly choked flow
  • Familiarity with Reynolds number and its implications on flow
  • Experience with iterative calculation methods for fluid systems
NEXT STEPS
  • Research "orifice plate calculation methods" for detailed formulas
  • Study "choked flow in liquids" to understand its effects on pressure and flowrate
  • Explore tools like the TLV water flow rate calculator for practical applications
  • Learn about pressure drop calculations across orifice plates in fluid systems
USEFUL FOR

Engineers and technicians involved in fluid dynamics, particularly those working with pressure reducing systems in marine or industrial applications. This discussion is beneficial for anyone needing to optimize flowrate and pressure management in systems utilizing orifice plates.

clint84
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Hi,

I would like to know how would i be able to solve a problem involving two (2) pressure reducing orifice plates in series with seawater as medium.

I know the orifice diameters, the supply pressure, but i don't know the overall flowrate, and pressure after the orifice plates.

The Ship's firemain which is the source of pressure = 9 bar, has a branch which is connected to an
Oil cooler downstream. Downstream from the oil cooler the pipe discharge into the sea (3m below waterline). The total length of branch pipe is 10m and the supply point is 5 m above the discharge point, with the discharge point being 3 m below waterline.

If I know the pressure but don't know the pressure drops or flowrate, is it possible to solve for the flowrate and pressure after the multiple orifice plates by hand?

I'm guessing this would be an iterative equation because the pressure drop over the orifice plates will be dependent on velocity - which i don't know, and K, which is dependent on Reynold's number and also related to velocity. Is there a method to solving this problem?

The only standards i find are on flowrate measuring orifice plates which are not the same as pressure reducing orifices.

Any help would be much appreciated

Cheers

Clint
 
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The oil cooler will require a minimum flow and so you must design for that, with a safety margin.
You know your input pressure, outlet head, pipe sizes and the pressure drop across the oil cooler at that design flow.
The two orifice plates will have to each drop half the remaining pressure.
 
I already know the minimum flow into the oil cooler, but what if i wanted to calculate/estimate the resultant flowrate from reducing supply pressure from 9 bar down to 6, 4, and 2, keeping orifice plate dimensions constant?

The orifice plates in series at the moment are designed for a specific supply pressure and design flowrate into oil cooler. I want to know how the flowrate and pressure drop over the orifices will change if i deviate from the design supply pressure, i.e. supply pressure is reduced significantly
 

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