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# Flow and Pressure Drop Relation

## Flow and Pressure Drop Relation

(OP)
How flow change with pressure drop? If P1 at the inlet of pipe=50 psig &P2 at end of pipe is based on pr. drop and flow is x for e.g. Now if i put orifice in pipe due to more delta P should flow increase to > x since flow is proportional to delta P? Why by putting orifice then flow decrease???

### RE: Flow and Pressure Drop Relation

Putting an orifice in the line introduces extra frictional losses.

So now you have P1, P1a, the orifice, P2a, P2.

Depending on what stays the same the flow will either increase, stay the same or decrease.

You haven't said what happens to P1 and P2 when you put the orifice in.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Flow and Pressure Drop Relation

Do not think of flow, system pressure and pressure drop as independent of each other. All 3 are related.

Increasing pressure drop by adding the orifice will tend to reduce flow. If you try to force the same flow, then system pressure must increase. If system pressure can not increase, ultimately flow will reduce.

The converse is also true.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

### RE: Flow and Pressure Drop Relation

OK, re reading this again a bit more closely, you say delta P (P1-P2) increases and then you insert an orifice plate, if the flow reduces, then the pressure drop across your orifice for the same initial flow x is higher than the increase in delta P.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Flow and Pressure Drop Relation

@zamakaze,

I think you need to obtain some general knowledge of hydralic flow in pipes. Your question is very basic and just throwing a formula at you seems a bit "risky". Besides there seem to be some language barrier and a good textbook in your own language would probably be the best option for you.

Also, hove to remember that there is a big difference between restriction orifices and orifices used for flow measurement.

Best regards, Morten

--- Best regards, Morten Andersen

### RE: Flow and Pressure Drop Relation

zamakaze,

On your next trip to Tim Hortons or the like, obtain a straw. Blow through the straw as hard as you can. Then, pinch it almost closed near the middle with two fingers while blowing through the straw as hard as you can again.

Now, you know the answer, right?

Good Luck,
Latexman

### RE: Flow and Pressure Drop Relation

zama,

the flow is the result of the total pressure drop in your pipe, the flow is proportional to the square root of the pressure drop, more pressure drop the less flow, unless you change the piping or the supply pressure.

### RE: Flow and Pressure Drop Relation

Just remember that a pump puts out flow, not pressure. Pressure is the resistance to flow.

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