Question on combining 2 streams of different pressure

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Discussion Overview

The discussion revolves around the problem of mixing two fluid streams at different pressures (10 bar and 30 bar) in a cost-effective manner while preventing potential damage to a low-pressure pump. The scope includes theoretical considerations, practical solutions, and engineering principles related to fluid dynamics.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests using a tank at the intersection of the two streams to store them before combining, but questions its cost-effectiveness.
  • Another participant proposes using a throttling process on the high-pressure line and references Bernoulli's equation to consider the relationship between pressure, pressure drop, and fluid velocity.
  • A follow-up inquiry seeks clarification on whether a throttling valve is meant and how it relates to fluid velocity and pressure changes, while also mentioning Pressure Reducing Valves (PRV) and questioning the differences between throttling valves and PRVs.
  • Another participant recommends protecting the low-pressure pump with a check valve, asserting that as long as the mixing point pressure is below 10 bar, there should not be an issue.

Areas of Agreement / Disagreement

Participants express various approaches to the problem, indicating that multiple competing views remain regarding the best method to combine the streams safely and cost-effectively. There is no consensus on a single solution.

Contextual Notes

The discussion includes assumptions about the pressure conditions at the mixing point and the implications of using different types of valves, which may not be fully resolved. The effectiveness and cost implications of the proposed solutions are also uncertain.

sero2000
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Homework Statement



Well I was given an assignment to find ways to solve the the problem of how to mix the 2 streams in the digram together at the lowest cost possible.

The pressures of the 2 streams that are being mixed together are 10 bar and 30 bar

The fear is that instead of combining into 1 stream, the flow from the 30 bar will flow into the 10bar stream and damage the pump

[PLAIN]http://img94.imageshack.us/img94/1051/drawing1x.jpg

Homework Equations





The Attempt at a Solution



The only way i can think of so far is to just add in a tank at the intersection where the 2 streams meet to store both streams before i pump them out as 1 combined stream. But however i don't think it is very cost effective. So i stuck to as how i can continue.
 
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What about using a throttling process on the high pressure line.

Also, think about relationship between pressure (and pressure drop) and fluid velocity, e.g., Bernoulli's equation.

Certainly the two streams would have to enter a chamber with a pressure less than 10 bar.
 
Astronuc said:
What about using a throttling process on the high pressure line.

Also, think about relationship between pressure (and pressure drop) and fluid velocity, e.g., Bernoulli's equation.

Certainly the two streams would have to enter a chamber with a pressure less than 10 bar.

Hey thanks for the reply :D

Hmmm... By throttling process do u mean adding in a throttling valve? I am not sure if i gt it right but a throttling valve will change the velocity of the fluid and so based Bernoulli's equation the pressure would also change?.

Also while searching i also came across Pressure Reducing Valves PRV.

Is there a difference between the the throttling valves and the PRV?
 
If you are worried about the low pressure pump, just protect it with a check valve. As long as the pressure at the mixing point is less than 10 bar, you won't have a problem.
 

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