Refrigerant charge, calculation

[PaulLag]

Hi there !

hope you had an happy Thanksgiving, US folks !

Please, I am contacting you for following topic

I have been asked to calculate the refrigerant charge in an air cooled condenser.

As per my knowledge , the rule of thumb is

- if condenser is flooded, you calculate the internal volume multiplied by liquid density
- if not you consider 1/3rd of this value.

where liquid density is the density of the liquid outside of the condenser.

Please, does anybody know a different calculation method or can suggest me some literature to review ?

Thanks in advance !

 

[berkshire]

PaulLag,

Here look at this.
B.E.

You are judged not by what you know, but by what you can do.

 

[PaulLag]

Hello
Mr Berkshire, many thanks for your tip
Indeed this is the way I know.

But if look for example to this catalogue

http://goo.gl/A0OdYZ

, page 24,table 10

or

You can find a table with refrigerant charge.
Does anybody know how these values are derived ?

Thanks

 

[berkshire]

Skimming through that table, that looks like the manufacturers initial charge is based on the internal volume of the condenser. Usually done by the weigh in liquid charge method on an empty condenser. Most often this information is stamped on a nameplate on the unit. It is not the final charge because the maker has no idea of the length of your line sets. However he does give you a value of pounds or kilos per hundred foot run, so you can derive that value yourself. With head pressure control valves you can flood to 100% if not then you need to find the lowest temperature the unit will run at and fill to 80% . your 1/3 or 33.3% would be a safe starting point to get the unit running before final determination of superheat. It is trickier to do this job with Horizontal condensers compared to vertical condensers, because there is far less convection around the coil. I have to ask, are you trying to find a pre charge for a new coil. Or are you trying to determine the volume for a repair?
B.E.

You are judged not by what you know, but by what you can do.