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2

# Two Liquids Mixing At Different Pressures

3 replies to this topic
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### #1 livewise04

livewise04

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Posted 26 June 2020 - 07:20 PM

I have an application as follows:

I have positive displacement pump 1 that is pumping at around 6 BPM ( through a 4" pipe) at pressure P1. There is another smaller positive displacement pump 2 that is pumping at around 0.8 BPM ( through a 1" pipe) at pressure P2. These 2 fluids mix at a point and are discharged to a open tank ( atmospheric pressure). I would like to know the pressure at the mixing point Pm.  Is there any empirical formula that i can use to determine the pressure at point Pm? Any guidance is very much appreciated. see attached schematic for more details.

#### Attached Files

Edited by livewise04, 27 June 2020 - 01:21 AM.

### #2 breizh

breizh

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Posted 26 June 2020 - 09:22 PM

Hi,

Did you try to apply Bernoulli equation ? You need to describe better your system ( pipe length , fiittings, altimetry  ) ,  pipe material ( rugosity ) and the physical properties of the fluid ( Ro, Viscosity) .

Good luck

Breizh

Edited by breizh, 27 June 2020 - 12:10 AM.

### #3 livewise04

livewise04

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Posted 27 June 2020 - 01:27 AM

Thanks Breizh. Could you please provide more details. I can use Bernoulli equation in just one stream ( for example, fluid from pump 1 to tank or from pump 2 to the tank). Now we have two different liquid converging at a point before eventually getting displaced to the atmospheric tank. How will it work here?

Another question:

Let's say the discharge pressure of fluid 1 is 120 psi and the discharge at fluid 2 is about 30 psi. Will there be an issue of the fluid pumped from P2, since the discharge pressure of P2 is small compared to dicharge pressure at P1? Will there be a proper mix?

Edited by livewise04, 27 June 2020 - 03:49 AM.

### #4 breizh

breizh

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Posted 27 June 2020 - 02:13 AM

Hi,

Let you consider the document attached I prepared a few years ago  ( pipes distribution) , review the set of equation applicable to your system and build an excel sheet similar to what I did .

In addition a pdf to calculate head loss for flows converging in a tee .

Hope this is going to work for your application

Good luck

Breizh

#### Attached Files

Edited by breizh, 27 June 2020 - 04:53 AM.