Quote Originally Posted by mad fridgie View Post
OK, keeping it simple, if we had NO superheat at the exit of the evap, would the flash gas in the evap have any effect on the net cooling of the room. (energy only)
Right time to jump in with both feet.

The flash gas is caused where the energy contained in the liquid refrigerant entering the TEV is used to lower the temperature of itself to get to the boiling point in the evaporator.

i.e. Te is -30*C, Tc 35*C subcooling 5K means as ref. enters the TEV at 30*C it has to drop temperature by 60K to boil. Ideally the temperature of liquid feed to the TEV would be as low as possible as this shifts the expansion line on a PE chart over to the left into the higher % region of liquid/vapor mix. If it was 100% that means the liquid at the TEV was already at -30*C. If it was you wouldn't really need a refrigerant circuit as you somehow had the means to get refrigerant at the same temperature as Te so you'd use that means instead.

So in answer the flash gas has no net effect in cooling the room. It only cools the refrigerant to the evaporators boiling point.

How does that sound?

Cheers,
Andy.