Suction/liquid heat interchanger

Techman

We recently started working for a new A.C. customer,the liquid line was in full contact with the suction line ,from the cond unit all the way to the evap coil(40'-45')and both lines were wrapped by Armaflex insulation.Why?Does anyone know of a benefit to this practice? Maybe ,saving the cost of insulating the liquid line as well? The attic is very hot!And attic venilation will be in their future,very soon!

bob_50

It

subcools the liquid which increases refrigerating effect in the evaporator and superheats the vapor in the suction line which reduces compressor capacity. Kind of six of one half a dozen of another. There was a time when manufacturers used to require us to solder the liquid line to the suction line. Suction liquid heat exchangers are still manufactured I believe.

Techman

Bob

Good morning,Which mfrg of AC says that? Just being curious! Walk-in freezers require a S/L heat exchanger which is about 18"long,and cap tubes systems are most times soldered to the suction line,but on AC systems I'm not familuar with that practice.Thanks!!

Empire_2

Good Morning Terry

If you look at you P&E charts additional sub-Cooling of the liquid line increases the net Ref. Effect.

Mike T.

bob_50

Tech

To be honest I can't remember. I'm talking late 50's. The practice was not unusual. It might have been Mueller or Westinghouse.

bob_50

Mike

What you say is true IF the heat removed in subcooling is rejected from the system. With suction, liquid, exchange the heat stays in the system.

Techman

wHICH WAY TO GO?

Thanks Bob! Hi Mike T! Its been months and months since the last time I was able to sit and be here ,amoungth's[?] all of you! Mike ,I think of you and your Dad ,quiet often ! I trust he and you are doing great! Happy "Fathers Day" to you ,both!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Ditto to you, Professor!Professor,what is the "braineact"side of this?

don_185

If

your metering device is in the outdoor unit then the liquid line becomes part of the evaporator.Its no longer a liquid line.
If not...................
I would think by wraping the two together for that long of a run you will lower your superheat maybe low enough to harm the compressor.

On the other side you will lose your colum of liquid one needs for proper valve operation.

bob_50

Don

isn't the liquid line usually warmer than the suction line? Heat flows from hot to cold. Wouldn't that tend to warm the suction line and increase the superheat and further subcool the liquid?

don_185

lol

You got me.I was wondering if anyone was paying attention.

So why would we want to increase the system superheat?
How can added heat to the suction line be of any benefit?

Other then reducing flash gas in the liquid line which I could see no reason why there will be any worry of that in a hightemp system.What purpose could it serve?