Freon leak vs. moisture

Techman

Hay Professor!! I was going to ask this question in class the other day but I didn't want to make a fool of myself in front of everyone. So I'll ask you now. As Freon is leaking out of a system ,low, medium, hi pressure leak, does moisture travel into the system? KindaSorta like salmon swimmmmming upstream?!?

icesailor

Stupid Questions:

The only stupid question is the one not asked.

If you were wondering, but afraid to ask, someone else was there with the same question but were too afraid to ask. Some others thought they knew the answer but would be wrong.

I'd like to think I know the answer but I'd like to have someone ask the question so I could find out if I was correct. Or if I wasn't, then I'd know the answer.

Never hesitate to ask a question, no matter how stupid you think it is. You have no idea how many people will be helped by the answer to the question you asked. You also have no idea how many people appreciate you asking and someone else giving the correct answer

Pick any topic on heatinghelp.com. Look at the replies. But look at how many people looked at the string.

Ask the question. Don't be bashful.

Eugene_Silberstein

No Moisture In.... Most of the Time

Under normal conditions, the answer to your question is No. As long as the pressure in the system is above 0 psig, you will not pull any air or moisture into the system.



If the system leak is on the high pressure side of the system, air and moisture will not be pulled into the system. The same holds true if the leak is on the low side and the pressure is above 0 psig.



However, if the leak is on the low side of the system, there is a good chance that, if the compressor is allowed, or forced, to operate, the suction pressure can be brought down to a pressure below 0 psig, thereby allowing air and moisture to enter the system.



So, if the system is off on Low Pressure, it's not a great idea to over-ride the low pressure control to "see if the compressor turns on". You may have just added moisture to the system!

unclejohn

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unclejohn

Dear Professer

I would think that vapor or moisture pressure would be the controlling pressure here and not system gas pressure, Since the system piping is dry and the outdoor air would normally have a higher moisture content I would think that moisture would enter the system even on the high side..

Eugene_Silberstein

The Thee Legged Stool of Moisture Flow

In order to have moisture flow, we need to have three things. We need a source of water, a path for the water to take and a driving force to push the water through the hole.



In the case of a leak in a refrigeration system, we have the source of water (the moisture in the air) and we have the hole (the leak site). What we are missing is the driving force.



In some instances, the driving force can be gravity or capillarity (capillary attraction), but neither are relevant in our refrigeration system scenario.



Since we have pressure pushing out of the system, our driving force is not in the right direction for moisture to be pushed into the system.

unclejohn

I was

On a job many years ago at a Baush and Loam lab that made eye drops. The lab had to have a very low humidity. There were actually two A/C units and evaps were one in front of the other. The discharge of one into the supply of the other. Well the RH was still to high in the room and the job was done as specked. Some real smart guy came out and explain that even though the supply duct to the lab was pressurised moisture was entering the duct. We sealed the supply and the job ran as designed. And I don't see the difference between air pressure and refrigerant pressure.

Eugene_Silberstein

When you say...

When you say "sealed" the duct, are you referring to insulating/wrapping the duct?

Techman

Dry vs. wet

Is there some point ,say 10 psig, that the moisture in the air says "I'm going over to that dryness and balance out this moisture inbalance " ? and the moisture does overpower the Freon leak? Like moisture can talk, lol!

Harvey Ramer

This is way to interesting to leave alone!

This is my understanding of how it works.



In order to grasp this we must first realize that air and water vapor are 2 completely independent gasses. One does not hold the other. They merely coexist in the same space along with many other gasses. The only relationship the gasses have is the transfer of kinetic energy from molecules in an attempt of mother nature to reach a thermal equilibrium. 

Dalton's Law explains to us that if we apply mechanical force to a mixture of gasses in a confined space, each gas will act independently of each other as if the other gas did not exist in that space. Therefore if we would have an evaporator fan pushing air through ductwork but the evaporator coil is removing all the water vapor, the partial pressures of the water vapor inside the ductwork would be zero. Regardless of the pressure of the air. Meanwhile outside the duct, if we have a 70°F air temp @ 50% humidity, the partial pressure of the water vapor will be .18 psi.



So yes. Water vapor could be entering the duct at the same time air is exiting the duct.



Any thoughts? Please correct me if this is not accurate.



Harvey

 

Eugene_Silberstein

Dalton is an Interesting Individual

Very good point Harvey.



The only issue is that Dalton's law refers to different gases in a given volume or space, which means that there are no interconnecting pipes or barriers within the space.



The situation at hand is referring to two isolated spaces, as the interior of the duct and the exterior of the duct are not unobstructed from each other. So, in essence, we are talking about two separate volumes here.



I love it when you guys send me back to the books!



I will dig out my old physics books later on (I'll have to dust them off first!) and take a closer look.



I'll let you know what I find!

Techman

3 amigos

Whenever I hear of "Daltons Law" I also think of "Charles Law" and "Boyles Law" . Do those last two guys enter into air as much as Dalton? How? Perfect example of applying"Dalton Law", Harvey, Professor,!!!!!!!. My last apprentis and I were going over those 3guys recently.

Eugene_Silberstein

The Verdict is in!

I spoke with two of my colleagues from the physics department here at the college, and the answer is.....

Moisture cannot enter the system if the presure in the system is higher than the pressure outside of the system.

We must look at the total pressure in each area (inside the system and outside the system) to determine the direction of fluid flow. Fluid flow refers to liquids and gasses. Even though the "water vapor pressure" is higher outside the system than inside the system, given the absence of water vapor inside the system, the total pressure in the system prevents water vapor from entering.

This will hold true unless the pressure inside the system drops to atmospheric, at which point, "all bets are off".

Thanks to Professors Janet Haff and Muhammed Khalik for confirming!



Enjoy!

Harvey Ramer

Well Then.

That is that!



I'm awful glad that I'm wrong! It makes things a lot easier and less confusing.



Thanks Professor, for digging into this and finding the answer. Now I may be able to sleep once again ;-)



Harvey

Techman

DITTO THAT, Harvey

Thanks , Professor, You and your cohorts just shot a 44 year belief in the butt!!!!!!!! I was instructed that way in 72' or so and it KindaSorta made sense. So, I believed it! So, I solemnly swear to amend my dirty nasty way of thinking! Hat's off to You and Them.



Harvey, I really like that "sleeping thing"  LOLALOT. Dalton down , Charles next.

Harvey Ramer

A little time.

Give me a little time Terry. I'm 30 years and 500 books behind ;-)



Harvey

pecmsg

Venturi

Just to throw the Monkey Wrench in

A long shot but wouldn’t air / moisture get drawn in with a “Venturi Effect” / Bernoulli equation

Loved the class Professor

Techman

The Battle

Hi Professor,I was talking to Al Maier of Emerson Flow Controls and says hello and that he agrees with you on this .

Eugene_Silberstein

Glad to Hear

Al is a good man.



I'm just glad that we were able to clear this up. I'm all about getting accurate information out to my peeps!