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Jai
31-01-2002, 08:36 AM
I am working on a 407c system that has lost some of its charge.I can't tell the percentage that was lost. I would like to find out if the composition (chemistry) of the remaining LIQUID in the system has changed. If I remove ONLY the LIQUID (not vapour) from the system, would this liquid be 100% R407C.

Prof Sporlan
31-01-2002, 06:50 PM
If I remove ONLY the LIQUID (not vapour) from the system, would this liquid be 100% R407C.
If the composition of R-407C (R-32/R-125/R-134a, 23/25/52 percent by weight) has changed in the system, it will also change for the liquid R-407C in the system.

Normally, liquid or vapor leaks do not cause sufficient fractionation to be a concern. Leaks at the evaporator and condenser coil (where refrigerant is in its two-phase region) can be more of a problem.

Verifying the pressure-temperature relationship of the refrigerant blend would be in order if one suspects composition has changed significantly.

herefishy
01-02-2002, 12:21 AM
Correct me if I'm wrong, Prof.,

But having the conversation regarding fractionization with a refrigerant mfgr rep., it was stated that the conditions under which actual fractionization could actually occur would have to be entirely "static" (for lack of a better word), in relation to constant temperature and/or agititation in order for a measureable amount of fractionization to occur.

As such, these conditions are rarely found in field service. being that equipment is typically in service and operating at the time that such occurances (leakage) occurs.

I concern myself with such matters when addressing refrigerant leaks on systems containing blends when re-activating systems which may have been "moth-balled", or inactive for some time.

In the end, I was left with the impression that the affects of fractionization are not that significant in the realm of practical, or everyday refrigeration/leak reaair of equipment "in service". That furthermore the refrigerant industry has lessened somewhat it's emphasis on the fractionization issue in the realm of "everyday service/repair.

Prof Sporlan
01-02-2002, 02:36 AM
But having the conversation regarding fractionization with a refrigerant mfgr rep., it was stated that the conditions under which actual fractionization could actually occur would have to be entirely "static"
The Prof can generally buy into this argument, but with the possible exception of a two-phase flow leak. A refrigerant blend flowing thru the evaporator will being evaporating at a low temperature, and continue to evaporate at higher temperature until it reaches saturated vapor (the dew point). The difference in these temperatures is the refrigerant temperature glide in the evaporator, and the reason it occurs is the more volatile components of the refrigerant blend boil off first. So if a leak exists at the inlet of the evaporator, one might expect the more volatile components to leak out, assuming refrigerant vapor and not liquid is leaking out.

But from a practical standpoint, the Prof doubts that your average refrigerant leak in an operating system could cause sufficient fractionation to cause problems.

Derek
01-02-2002, 08:59 AM
ISTR that ASHRAE data gives somthing like +/-2% tolerance on fluid properties so you have to loose a lot before you were left with R134a(?) perfromance.

Theres a number of papers showing R407C performance drops off with time and my only deduction is fractional loss.

Pressures and temperatures should be a reasonable guideline but having a sample tested is only valid at the time you took it and probably not worth the time of money.

If your loosing cooling perfromance and there's no other explaination then recover and recycle (if you have the facility or supplier access).


Derek:cool: