Hoses for phase-change

[DaBit]

I am still not sure what kind of hoses I could use for my cascade.
Basically, there are three suitable hose types:

1) Rubber with barrier lining to prevent leakage
2) PTFE with stainless steel braid.
3) Pure stainless steel hoses.

Barrier lined rubber hoses are not very suitable since their useable temperature range does not go lower than -40C / -40F

Stainless steel braided PTFE hoses seem already a better choice, and in fact it is what our phase-change guru Bowman uses. But I have read that PTFE is a permeable material; it leaks small amounts of gas over time.

For example, check page 8 in this document
There they test a meter of hose with 30 bar (~450 psi) helium. To prove their hose superiority, that state that permeability has decreased from 317 milliliters/hour to 138 milliliters/hour. Thus, it would take 27 hours to leak a gallon of gas with Bioflex super-duper-hose. Damn, that's much.
Now, we use lower pressures and larger molecules, but these only move out slower.

It might lead to nice explosion risks when using a closed and airtight mainboard housing like I do, and ethane as the low stage refrigerant.


The last hose type is full stainless steel. Do these hoses have their share of problems also?

[]JR[]

How about using a solid copper vibration eliminator to get enough play to put the head on the chip? Found these which are braided but ive seen some which are like a concentina of solid copper, im still looking for a pic...

]JR[

[DaBit]

What would the bending radius of these thing be? They can be used to the evaporator. Then I still have to route most of the piping with copper, but at least I reduce the risk of breaking the processor due to mechanical stress.

But it seems to me that these things are similar constructed as stainless steel hose.

[bowman1964]

every flexable hose made for refrigeration has a permeationn rate.but they are alot of variables involved in the way they test.

for a positive leak proof system the only thing is stainless convoluted tubing.that is for sure.

like has been said before everthing is give and take.

you just have to make a deciesion......

do you want a positive no leak system that will withstand 50 years of leakproof sealing.that will break after you bend it enough times.

or do you want a flexable hose ,able to withstand multiple bending and just will leak down in 10 years or so.

it is always give and take.

for a computer system that will have multiple mounting and removal times..i will be moved on to bigger and better things in 10 years or so.or however long it takes.

i have some stainless convoluted tubing i may try on the cascade .very simerlar to the prommie stock tubing.but i havent decieded yet on if i want to try it or not.

[berkut]

Remember that oil also makes hoses more "gas tight"

I think that PTFE hoses like bowman, baker and I use are the best (at least those wich i seen)

[DaBit]

Originally posted by bowman1964
every flexable hose made for refrigeration has a permeationn rate.but they are alot of variables involved in the way they test.

Indeed, but the leak rate indicated in the document above surprised me. Sure, it's helium. Sure, it's a very high pressure. But I still consider the permeation rate very high.

for a positive leak proof system the only thing is stainless convoluted tubing.that is for sure.

Do you mean stainless steel hose or pipe?

or do you want a flexable hose ,able to withstand multiple bending and just will leak down in 10 years or so.

I can live with 10 years. I can even live with a single year.
The problem is: when ethane leaks inside my mainboard box, it cannot escape. And everything boils down to ethane or ethylene in the low stage due to the restrictions regarding fluorinated carbons. I simply cannot recover these high pressure refrigerants.

for a computer system that will have multiple mounting and removal times..i will be moved on to bigger and better things in 10 years or so.or however long it takes.

Well, you know me long enough to know how often I change my systems

Remember that oil also makes hoses more "gas tight"

I think that PTFE hoses like bowman, baker and I use are the best (at least those wich i seen)

In my cascade there won't be much oil circulating through the hose.

Has anyone of you ever tried convoluted stainless steel hose? I know Herefishy uses it.

[Marci]

S'wot I've ordered and am waiting to arrive...

[DaBit]

Good. I will use 3/8" copper during testing, but after testing I definitely need something else. I really want to hear your results.

offtopic: I just ordered a bottle of ethane for the cascade >. All they need to do is to check me if I have a criminal record.

[berkut]

Dabit ]:-> How much did it cost ? Is it cheaper than R23 i found?

[bowman1964]

dabit you would never notice a leak though the hose,by the permeation rates.but it depends on a lot of varables,

you can buy convoluted stainless steel tubing here in the states for gas opperated appliances.comes in 30" lenghts i have found so far.

the same thing prometia uses.


i have been looking though some of my books,looking for a permeation rate for tfe hoses,they were never really tested for these applications with the differant refrigerations we are using.so there is no data on the subject.i can find rates for rubber based hoses.which for a 3/8 id hose with r134a has a permeation rate of .07 pounds per year @212f

[]JR[]

http://www.flexiblehose.co.uk/smoothbore2.htm

out of interest ive found a uk supplier for some suitable cascade hoses, they can come with bspt fittings too...

]JR[

[DaBit]

EUR 68,- for 3kg ethane, purity 2.4 (99.4%). This excludes all extra cost such as transport cost, dangerous goods tax, minimum order costs, cylinder rental, etc.

This seems just as expensive as R23, but it is not. Hydrocarbon charge is usually only about 40% by mass of fluorinated hydrocarbon charge.

And ethane is the better refrigerant of the two. R23 has some pretty bad properties. Have you ever drawn a PH chart for it? I did:



See and shiver. This is at -100C evaporating, -30C condensing, 5K superheat and 5K subcool. Thus, no suction gas<->liquid line heat exchanger.
As you can see, discharge temperature is already almost 140C, about the limit of the average compressor. And this with the compressor sucking in -95C gas.
With SG<->LL HX, discharge temp rises to above 200C, way too hot.

With ethane, we are talking 75C discharge without SG,->LL HX, and about 110C with efficient SG<->LL HX.

Ethane also needs a lower compression ratio and has a higher volumetric capacity.

But yes, it is flammable...

[DaBit]

Originally posted by bowman1964
dabit you would never notice a leak though the hose,by the permeation rates.but it depends on a lot of varables,

OK, if you say so, I believe.
What about temperature range. I intend to use those hoses for ethane transport. And I hope to reach the -100C evaporation someday. This doesn't mean that the hose must transport -100C vapour, but -80C would be a reasonable guess.

you can buy convoluted stainless steel tubing here in the states for gas opperated appliances.comes in 30" lenghts i have found so far.

I have been looking for them in The Netherlands, without luck. Here they seem to use exclusively a rubber kind of gas hose.

The big advantage of that hose would be that I could braze it directly onto the 3/8" copper pipe, right?

Also, bending radius of convoluted SS hose is not bad. Usually somewhere around 140mm dynamic and 40mm static.

i can find rates for rubber based hoses.which for a 3/8 id hose with r134a has a permeation rate of .07 pounds per year @212f

That sounds acceptable, but barrier lined rubber hoses are not by far as permeable as (P)TFE hoses.

[herefishy]

DaBit,

The plumbing department in your hardware store will have the stainless steel gas connectors that you will want to use. Look in the water heater department.

[charlie]

no, no, no and no,

THESE are the sh*t

Vacuum insulated refrigeration lines

[Weapon]

IMO, it seems that the best solution to your problem might be a combination of the two types of hose/tubing that you mentioned.

I have no idea how your system is setup with the sealed mainboard box so it is hard to speculate on how this would work but would it be possible to use a section of the convoluted SS type, mount a flare fitting onto it and then connect the shortest possible length of SS braided/PTFE hose to make the last jump?

that would minimize the loss through the PTFE/SS hose (very small overall surface area for the gas to leak through) and possibly allow enough flexibility to where the convoluted SS tubing wouldn't break after system change-outs...

[DaBit]

Originally posted by herefishy
[B]DaBit,

The plumbing department in your hardware store will have the stainless steel gas connectors that you will want to use.

Nope, these hoses are not common in The Netherlands
But I already found a supplier. They only can't tell me the I.D.

no, no, no and no,

THESE are the sh*t

Vacuum insulated refrigeration lines

Where, what, how, how expensive?
Looks good for everything except the last piece.

IMO, it seems that the best solution to your problem might be a combination of the two types of hose/tubing that you mentioned.

An even better combination: 3/8" pipe until the last feet/30cm or so, and convoluted SS hose from there.

[herefishy]

What's convoluted here, is the issue. The tubing is not "convoluted", it's corrugated..... deleted!

Dabit, the SS CORRUGATED tubing (gas connect) is $6.00 for an 18" or 24" connector, here (US). By Golly, you PM me, and I will send the material (including the high-temp flux that you'll need) to you. Also, I find that 1/2"x3/8" pipe, fitting reducers best accomodate the transition from the SS corrugated tube to the copper suction (which typically is 5/8" O.D. but a swedge makes the fit )

You are a good brazier, right? You'll require 45% silver (along with the high-temp flux that I'll send ya') to accomplish the connections. Actually, today I brazed in a SS tube, and the 15% seemed to work even better for me )

If I MUST to send you all the "whole ball of wax", I may not do it for free.

PM me.

Let me know!

[]JR[]

Originally posted by herefishy
What's convoluted here, is the issue. The tubing is not "convoluted", it's corrugated..... deleted!

Like the middle bit of an accordian, i wasnt sure what to call it

]JR[

[migginz]

would sliding the pipe inside hose with same ID as pipe OD and using 3 or 4 jubilee clips be safe?

[Weapon]

Originally posted by herefishy
What's convoluted here, is the issue. The tubing is not "convoluted", it's corrugated..... deleted!

ummm. negative.

http://www.amazonhose.com/products.asp?id=61-1

convoluted says the catelog and the manufacturer.

[DaBit]

Corrugated, convoluted. Seems to be the same discussion as TEV vs. TXV.

Anyway, I can't help you since my English is not good enough for this

[]JR[]

Im pretty sure thats not the type of hose herefishy is talking about though....

]JR[

[herefishy]

corrugated stainless steel tubing

http://www.oxinst.com/SCNPSC482.htm

convoluted stainless steel tubing

http://www.artifex.org.uk/


It appears that convoluted and corrugated are references to the same material. I checked my Funk and Wagnall's, and actually convolution is to twist / fold, and corrugate is to bend into parallel ridges.

I guess that the terms are interchangeable in reference to the material. I learned something ! Maybe in the US, we more commonly use the term convolute as a verb, as opposed to an adjective. In my search, I noticed that the convoluted tubing is a UK site.

..sorry 'bout that.

[DaBit]

Whatever; these are the hoses I want