How to calculate refrigerant charge required?

[refriengr]

Can someone please suggest how to calculate amount of refrigerant charge required in Dx system with flooded condensers?

Thanks.

[icecube51]

use COOLPACK.its free;)

nice program for calculations.

grtz, Ice

[US Iceman]

The total required charge for refrigerant in an air-cooled condenser depends on several things:


Will the condenser have head pressure control valves? I'm assuming it does since you mentioned flooded condenser.
If so, what is the lowest air temperature that will be encountered during operation? The colder the air is, the more refrigerant it takes to block off the condensing surface.
The safest way is to use 100% of the condenser internal volume...

[GXMPLX]

Suggestion: First figure out what size of condenser you need in summer and winter conditions. The volumetric difference between the two is about the amount of liquid you need to flood the condenser in winter (try to use the same type of condenser if possible). Calculate the minimun subcooling you need to compensate for the pressure drop to the last expansion valve, chech condenser manufacturer's data to see how much subcooling it delivers. The differens is the minimun height you must have at the receiver, calculate the volume of liquid refrigerant in it. Add the volume of all liquid lines, add suction side volume times density of suction refrigeran in its average condition, if you don't have manufacturer data for condensers an evaporators, add 30% of condenser pipe volume and 70% evaporator pipe volume. MULTIPLY BY THE DENSITY OF REFRIGERANT AT AVERAGE HIGH SIDE CONDITIONS (USUALLY CONSENSING CONDITIONS) Think of a number between 1 and 10 and add that percent of what you calculated above (this is called a safety factor). If you are charging a perfectly working system the minimum charge should be such that you get enough SUBCOOLING at the outlet of the receiver to feed the expansion valves but you have to do this at maximum thermal load. Please remember it's a suggestion!

[US Iceman]

To charge a system using a flooded condenser; it should be charge at maximum capacity at the coldest temperature. Otherwise you won't know if you have enough refrigerant in the system to block off the condenser surface.

[Shaukat]

see boiling point of refrigerant,

[frederick Smith]

Charge system to no more than 80% of receiver capacity after pump-down. This provides sufficient refrigerant for low ambient operation without overcharging unit.

[Peter_1]

use COOLPACK.its free;)

nice program for calculations.

grtz, Ice

I don't think Coolpack can do this for you

[Peter_1]

Can someone please suggest how to calculate amount of refrigerant charge required in Dx system with flooded condensers?

Thanks.

What do you mean in fact with a flooded condenser?

[desA]

I don't think Coolpack can do this for you

It can't.

The difficult part about accurate refrigerant charge determination lies in understanding the refrigerant density in the 2-phase regions of condenser & evaporator.

I have developed some software, still currently on trial, for estimating the refrigerant charge for simple refrigerant loops. It's been found to be pretty accurate, thus far - based on test results.