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gwapa
14-09-2009, 01:33 PM
Dear Friends
The following statement was taken from Carlyle compressor selection software.

Design Return Gas Temperature (RGT):

A data field for entering the design RGT for the refrigeration system. This temperature is generally selected as 25 ºFdegrees for Low Temperature applications and 40 ºFdegrees for Medium Temperature applications but may be any temperature equal to or greater than the SST (Saturated Suction Temperature) and less than or equal to 65F (65F is the default).

It is a very wide criterio ¿ Could somebody make this criterio narrow?
If I have -35ºC SST/ Condensing at +40ºC and using screw compressor,subcooling and economizer, which RTG should I select?
I appreciate your very kind comments
Best regards
Gwapa

oldesky
15-09-2009, 06:09 AM
I have always used a rule of thumb of not more than 20K suction gas return. I think that equates to about 35R in imperial.Basically if the elevated RST is not producing useful cooling your cop will decrease. Also, especially at low SST on some refrigerants, High RSTs will produce high discharge temperatures that can cause valve coking and oil carbonising

gwapa
15-09-2009, 08:06 PM
Thanks Oldesky
When you specify 20K=36R, it is over the SST.
that is RGT=SST+20K

Carlyle specify -3,9ºC for low temperature and 4,4ºC for media temperatura. But it could be any between SST and 18,3ºC

So you will be a little higher if you figure aout with 20K

I appreciate your very kind answer
Regards
Gwapa