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# Calculating Volumetric Flow Rate Out Of A Small Tank Based On Outlet D

11 replies to this topic
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### #1 noobeng

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Posted 20 September 2018 - 12:35 PM

Hi,

I am trying to determine the volumetric liquid flow rate out of a tank under 10 bar of N2 pressure.

Vessel details:

Internal Diameter = 0.5 m

Height = 0.51 m

Liquid level = 50 L / 0.255m

liquid density = 1.005 kg/l

Liquid viscosity = 100,000 cP

I was wondering if you can guide me towards how to calculate the volumetric flow rate at various outlet diameters.

I would like to then calculate the pressure drop over the specific length and hence determine the suitable pipe size.

The solution is non-Newtonian and shear thinning.

Any help would be appreciated.

### #2 Bobby Strain

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Posted 20 September 2018 - 03:07 PM

So, where is the liquid destination? One would normally depressure the nitrogen first, then proceed carefully to transfer the liquid.

Bobby

### #3 latexman

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Posted 20 September 2018 - 04:50 PM

Have you considered the Hagen-Poiseuille equation?  With the right assumptions and corrections, it'll come close.

### #4 breizh

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Posted 20 September 2018 - 08:33 PM

Hi ,

To add to Latexman's comment I've attached resources .

Chemical engineering Fluid mechanics from Ron Darby  or other textbook should help you.

Breizh

### #5 noobeng

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Posted 21 September 2018 - 06:12 AM

Hi , Thank you for the replies. The liquid from Tank 1 is to be injected into Tank 2 for storage and processing. The N2 injection and pressurising of Tank 1 is to get rid of the need for a heated gear pump. What I'm struggling with is how to calculate the volumetric flow rate out of the tank to start with. I think I'm missing something very simple initially.

### #6 breizh

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Posted 21 September 2018 - 07:12 AM

Hi ,

You may find pointers using this excel sheet I prepared a few years ago .

Hope this is helping you and others

Breizh

### #7 Bobby Strain

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Posted 21 September 2018 - 09:12 AM

It's always a bad idea to do what you propose. You must protect the receiving tank from the high pressure when nitrogen breaks through.

Bobby

### #8 noobeng

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Posted 08 November 2018 - 11:03 AM

Thanks everyone for your responses. I have calculated the discharge rate using the Bird et al. equation with viscosity and used the traditional approach to calculate pressure drop in pipes which should be sufficient for this size.

It's always a bad idea to do what you propose. You must protect the receiving tank from the high pressure when nitrogen breaks through.

Bobby

Bobby, would regulating the max N2 P inlet to below the tank design P reduce risks? I will have a precise flow meter installed so the P can be reduced as the V in tank 1 is reduced.

### #9 Bobby Strain

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Posted 08 November 2018 - 05:18 PM

Regulators fail.

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Posted 08 November 2018 - 07:53 PM

Hi all, I was following the discussion and found very interesting. Upon trying to figure out the calculation, I'm unable to access any attachments. Can you help me how to access them.

### #11 breizh

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Posted 10 November 2018 - 01:03 AM

Hi,

Just click on them and save them . You may have issues with your computer or the policy is not allowing you to download files !

Good luck,

Breizh

### #12 Sharma Varun

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Posted 12 November 2018 - 03:21 AM

Thanks everyone for your responses. I have calculated the discharge rate using the Bird et al. equation with viscosity and used the traditional approach to calculate pressure drop in pipes which should be sufficient for this size.

It's always a bad idea to do what you propose. You must protect the receiving tank from the high pressure when nitrogen breaks through.

Bobby

Bobby, would regulating the max N2 P inlet to below the tank design P reduce risks? I will have a precise flow meter installed so the P can be reduced as the V in tank 1 is reduced.

Regulators fail.

Normally in such cases, we design downstream system relief (say in this case tank 2 vent) for gas blow bye case. My observation here is in our practice based on various HAZOP studies which I have attended, we do consider failure of PCV where control loop is involved but we do not consider failure of PRV which is basically a mechanical device with less chances of failure.

I request other forum members to share their views or experiences.