Time to fully discharge a Chiller due to leak - Mechanical - Engineer Boards
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# Time to fully discharge a Chiller due to leak

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Not an HVAC engineer but was hoping someone here could help me figure out a problem for my master's program. Given the following:

1) Initial Freon charge in pounds

2) Initial pressure (psi)

3) Diameter of pinhole on chiller wall

Is there an equation I can use to calculate the total time it takes to fully discharge a chiller (complete loss of pressure)? System is not running, just sitting idle.

Thanks guys! I've been scratching my noodle on this one for a while.

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If this were me, I would first try to estimate a discharge coefficient of the hole.  Then I would numerically step through pressure drops and integrate the mass flow rate of freon leaving the system (depends on if liquid or gas wherever the hole is, though).  From the known mass (or estimated) of freon in the system you can then figure out how long it took from the integral of flow rate across time.

This is a total shot in the dark at it (not my forte) but I think that would get you in the ballpark.

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On 5/29/2019 at 8:16 PM, SacMe24 said:

Not an HVAC engineer but was hoping someone here could help me figure out a problem for my master's program. Given the following:

1) Initial Freon charge in pounds

2) Initial pressure (psi)

3) Diameter of pinhole on chiller wall

Is there an equation I can use to calculate the total time it takes to fully discharge a chiller (complete loss of pressure)? System is not running, just sitting idle.

Thanks guys! I've been scratching my noodle on this one for a while.

I’m sure I’ve seen that equation before.  Did you try looking in the MERM?

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On 5/31/2019 at 6:40 AM, EngrPaper said:

If this were me, I would first try to estimate a discharge coefficient of the hole.  Then I would numerically step through pressure drops and integrate the mass flow rate of freon leaving the system (depends on if liquid or gas wherever the hole is, though).  From the known mass (or estimated) of freon in the system you can then figure out how long it took from the integral of flow rate across time.

This is a total shot in the dark at it (not my forte) but I think that would get you in the ballpark.

Thank you very much for the tip !!

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On 5/31/2019 at 9:28 PM, P-E said:

I’m sure I’ve seen that equation before.  Did you try looking in the MERM?

I did but didn't see anything of use there...I did find this though and believe it's pretty much what I need. Let me know if you'd agree:

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You also have to account for the dp/dt. This is going to be a differential flow/discharge rate. I do recall that there is a calc on that in the MERM in the section on differential equations, but it is for a simple tank discharge. It's going to be a lil different with compressible flow, however.

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On 6/3/2019 at 11:48 AM, SacMe24 said:

I did but didn't see anything of use there...I did find this though and believe it's pretty much what I need. Let me know if you'd agree:

That paper looks spot on. Good find.

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Thank you very much man... appreciate the comment.

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