Time to fully discharge a Chiller due to leak

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SacMe24

SacMe24

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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.

 
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.

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

 
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.
Click to expand...
Thank you very much for the tip !!

 
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.

 
We have to calculate the losses from leaks in refrigeration.  Most engineers figure this in air then convert to Freon.  Use the air tables in the MERM.  The velocity of the Freon through the pinhole with be Sonic velocity up to a ratio of the absolute pressures is .5?   

I mean the Mach Tables.

Isentropic flow of a perfect gas...   Depends on the ratio of specific heats.

 
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