subcooling ?

[scott13]

New, young and dumb. I had question in class the other night- would subcooling go up or down as ambient went down?
I think it would go down but I`m not sure?
Txv and no head pressure control. I can`t find it in any lit.
Thanks for any input.

[sparks]

The subcooling would increase with lower ambient temps.

[scott13]

I just watched a vid on split system from Trane and they said it would decrease. Anyone checked out the live engineers newsletter from Trane- split system piping design.I found it to be intresting but they didn`t go into details.

[sparks]

Originally posted by scott13
I just watched a vid on split system from Trane and they said it would decrease. Anyone checked out the live engineers newsletter from Trane- split system piping design.I found it to be intresting but they didn`t go into details.

Never seen the video, but I have been doing this for a little while. Not that that makes me an expert on anything, believe me there are many more people here with more knowledge that I. With that said here is what I know to be true.

The greater the temp difference between the hot gas and the cool ambient air the greater the ability to remove heat from the gas. Removing more heat, assuming the charge remains the same = increased subcooling. This would be true for a unit operating in its ambient range.

If your talking about a unit running drasticly below it's ambient design then I could possibly see that since the head pressure would be too low, gas too cool to remove the same amount of heat. I guess you also wouldn't have that greater temp difference between the condensing refrigerant and ambient air. But honestly I never took a subcooling measurement with a unit running in that condition. You would normally worry about economising (hvac) or getting that head pressure up with some kind of control(refrigeration).

[scott13]

Sparks, I think your right and the teacher was trying to make a point. So in theroy, one would have to raise head on a low ambient to maintain subcooling? I`m only talking about s.c. not txv`s or anything else.

[Shophound]

Originally posted by scott13
Sparks, I think your right and the teacher was trying to make a point. So in theroy, one would have to raise head on a low ambient to maintain subcooling? I`m only talking about s.c. not txv`s or anything else.


Head pressure control during low ambient conditions is done to maintain a proper pressure drop across the TXV(s). Under these conditions, subcooling isn't as vital as maintaining enough pressure and mass flow rate to keep everything operating normally under the given conditions.

Subcooling IS important during high ambient conditions in order to maintain a solid column of liquid to the TXV.

[airworx]

subcooling goes up as the ambient goes down and goes down as the ambient goes up. also as the load decreases and txv pinches off the subcooling goes up and as the load increases the subcooling goes down.

[scott13]

Airworx; I think the teacher was trying to make a point on s.c. and ambient. He noted no head pressure control and txv function, just theory stuff on condensers.
I would like to know what books you have to back up your statements. I`m just looking for some good books. I hope that didn`t come out wrong?
Thanks.

[snewman24]

>I would like to know what books you have to back up your >statements. I`m just looking for some good books.

One of the better books is "Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems" by John Tomczyk. Amazon.com has it for about $34 including free shipping (a real bargain).