R407c

[bersaga]

What are the repercussions of using R 407C for a medium temperature refrigeration application ? I'm aware of the temperature glide of 6-8K and possible fractionation that happens with this refrigerant. How about design and field issues ?

Design : Evaporator and Condensor selection - need to oversize ?

Field : Leakages - how do you manage this ?

Some air-conditioning manufacturers claim that R 407 C is a very efficient refrigerant because of the glide - the compressor suction 'sees' a higher suction temperature and so does not have to 'work ' as hard as say, if R22 is used. But then in the condensor, the condensing temperature also progressively drops and may approach the ambient - so you may need a higher design condensing temperature - and off goes your efficiency advantage , right ?

Any views/assistance appreciated ?

[Andy]

Hi Bersaga
407c works well at high temperature ranges. My most recent experience is on water to water heat pumps with 2 deg C evaporation and 52 deg c condensing, with COP in the range of 3.8, so you could say it works well there. Medium temp is proabably alright, but you would have a little both controlling your evaporator flooding and your sution superheat, I would say leading to less than ideal (high) superheats and some reduction in effeciency.
Regards. Andy

[bersaga]

Thanks Andy - but say , on an application that requires -15 C evaporating temp. R407 C has a glide of 6-8 K(or more) at that point. Do I select a TXV rated at -15 evap or look for some sort of average ?

[frank]

Have a look at this from Copeland http://www.ecopeland.com/Literature/...0100_Glide.pdf

Frank

[Andy]

Hi Bersaga,
from reading Frank's Copeland document I would say use Dew point to set the expansion valve and Mid point when selecting compressors and matching capacities.
Kind Regards. Andy.