Corrugated stainless steel tubing technical data

[Edwin Croissant]

I have found a supplier for corrugated stainless steel tubing in Europe. Prices from € 2,35 per meter.

corrugated tubing.jpg (25.98 KiB) Viewed 5797 times

This type of tubing is used in solar heating equipment. Link to the supplier and a direct link to the product page.

Technical data:

The equivalent diameter is the diameter of a straight tube with the same surface area as the corrugated tube.

[DAD300]

Nice chart Edwin...

[FullySilenced]

Dad did you see they make premade heat exchanger coils from it as well same company..

FS

[Edwin Croissant]

The problem finding this information was that this stuff goes under so many names. Searching on the German word Edelstahlwellrohr did the trick.
One meter of DN8 (12 mm OD) will knock down 2 kW and can be made to fit inside a 50 mm tube with a length less then 20 cm |(I hope ).
Another application I can think of is to use 5 meters of DN12 inside a 100 mm plastic drainpipe with a computer ventilator as a radiator and a mini brushless pump to to circulate the cooling water.
It is also used to make an immersion worth chiller by hobby brewers.

[Edwin Croissant]

I tested a small condenser made from DN8 wellenrohr.

I used two Chinese made k-type Teflon line thermocouples ( 0,61 € each) to measure the inlet and outlet temperature, I checked the temperature readings with a Hanna Checktemp 1 (0,2 ºC accuracy) and found them within 1 ºC. Flow was measured by weight.

Objective was to measure the heat transfer coefficient, to find out if the flow direction made any difference and to find out what improvement a ss scrubby would give.

I used a 2000W (measured 1700W) wall paper stripper as steam source.

The results:
[tr][th]Cooling water[/th] [th][/th] [th]Bottom (center) in[/th] [th]Top in[/th] [th]Bottom (center) in with scrubby[/th] [th]Top in with scrubby[/th][/tr] [tr][td]Flow[/td] [td][align=center]kg/min[/align][/td] [td][align=center]0,298[/align][/td] [td][align=center]0,308[/align][/td] [td][align=center]0,386[/align][/td] [td][align=center]0,384[/align][/td][/tr] [tr][td]Delta T[/td] [td][align=center]°C[/align][/td] [td][align=center]37,8[/align][/td] [td][align=center]39,5[/align][/td] [td][align=center]43,3[/align][/td] [td][align=center]51,0[/align][/td][/tr] [tr][td]Knocked down power[/td] [td][align=center]Watt[/align][/td] [td][align=center]785,9[/align][/td] [td][align=center]848,8[/align][/td] [td][align=center]1166,1[/align][/td] [td][align=center]1366,3[/align][/td][/tr] [tr][td]Heat transfer coefficient[/td] [td][align=center]W/(m²*K)[/align][/td] [td][align=center]490[/align][/td] [td][align=center]535[/align][/td] [td][align=center]770[/align][/td] [td][align=center]1000[/align][/td][/tr] Remarks:
Outer diameter is 50mm, total length ~60cm, effective length ~49cm. Weight of the condenser is 67 grams, weight of the scrubby is 9 grams.
Cooling water inlet temperature was ~17 ºC and during the last test the condenser was able to knock down all steam.

[DAD300]

And this means...????

[skow69]

Scrubbies are cool.

[Maritimer]

And this means...????

This means that having the coolant flow going from the bottom to the top of the condenser is inferior to having it going from top to bottom.

And using a scrubby increases the heat transfer coefficient.

Going from top to bottom with a scrubby compared to going from bottom to top without a scrubby increases the heat transfer coefficient by 1000/490 X 100 = 204%.

Or, knocked down power by 1366.3/785.9 X 100 = 174%.

Edwin, interpretation?

M

[DAD300]

Ahhhh...thank you. I can easily change the flow direction...

Seriously, all of mine have a scrubbie at the top. I thought it was to keep the bugs out!

[FullySilenced]

Well it looks like a bug catcher on yours... since its not in the coil itself as it is in the test fixture...

I was alway told to intertwine the scubbies to disperse the vapor flow diverting it to the colder coils. The scrubbies also work as a heat sink for the cooling coils as well... pulling some of the cold into the vapor patch within the scrubbies...

But you knew all that already

[Edwin Croissant]

I apologize for not giving an interpretation right away but I was very tired last night. So please forgive me

I did not expect that reversing the flow would make a difference and I can't explain this.
It is common knowledge that scrubbies, if properly applied, raise the cooling capacity of a condenser but it was a surprise that the heat transfer coefficient was nearly doubled.
1000 W/(m²*K) is a number I can work with.

[DAD300]

Very nice work...I also apologize for not taking the time to interpret it...

[peacefuldavid]

This is consistent with the plate chillers I use to cool my wort after boil. Hottest (incoming) wort contacts plates with hottest (outgoing) water, coldest (outgoing) wort contacts with coldest (incoming) water. If coldest water hits hottest wort, then the temperature delta is big at onset, but nearly gone by exit. Whereas, the other direction keeps a larger delta throughout.

[Brutal]

This was an interesting read. Thank you for posting your work.

[Edwin Croissant]

Thank you Brutal

Next is to connect the condenser to a water cooler for a computer, a small pump, a flow meter , some temperature sensors and a Teensy 3.1 (an Arduino on steroids ) so I can read the values from the screen connected to the Teensy.

[engunear]

Hey, its great to see someone else with a thermocouple, a flow measurement and a calculator! And I love that pipe!

How many data points per setting did you take? What was your spread from one measurement to the next with the same settings? How much did the flow rate affect the measurements? The scrubbie test had 28% more flow than the non-scrubbie, and HTC varies with flow. How much did this affect the result? I found here http://homedistiller.org/forum/viewtopi ... 0&start=30 that my early attempts at measurement were all over the shop, but they settled down with practice and repetition. (There is a lovely quote from a physics lab I did once: "If you measure something once you know what you have. If you measure it twice and you get a different answer, you don't know what is going on." The student failed.)

Can we meaningfully compare this with a plate chiller? In a plate chiller both the cooling water and the wash/wort change temperature. In a condenser 80% of the power takes vapour to liquid with no temperature change.

I'm assuming that the black hose from the bottom of the photo goes to the wall paper stripper, and you measured the power into the stripper with your DVM? What is the heat loss down the black pipe? Does that affect the experiment? (I spent a day proving conservation of energy - getting a total knockdown power measurement to match my element rating. It took a lot of insulation and fiddling.)

The pic shows what I think is happening in an offset coiled condenser. You can check this with your trusty thermocouple. A more classic Nixon/Stone condenser is easier to measure than your nice tight one. The vapour comes in the bottom. There is a region where condensation occurs. It is uniformly at the liquid boiling point: any region that is cooler immediately gets heated by vapour. There is a region above that with air in it. The temperature drops quickly in this region. Then above that there is a scrubbie. The well known observation is that the scrubbie effects the condensation. I don't get it, and although its well known, I don't believe it.

BTW, don't think I'm dissing you or the expt. I love it!

[Edwin Croissant]

Hey, its great to see someone else with a thermocouple, a flow measurement and a calculator! And I love that pipe!

Thanks

How many data points per setting did you take? What was your spread from one measurement to the next with the same settings?

I did one test for each configuration. That's why I want to connect everything to my Teensy and redo the test with a better setup.

How much did the flow rate affect the measurements? The scrubbie test had 28% more flow than the non-scrubbie, and HTC varies with flow. How much did this affect the result?

I tried to keep the temperature increase constant so I needed more flow as I was able to knock down more vapor. I had some control with the kitchen faucet but it was a hit and miss thing. One thing I noticed that the temperature reacted very swift on the flow adjustments as there is not much water in this condenser.

Can we meaningfully compare this with a plate chiller? In a plate chiller both the cooling water and the wash/wort change temperature. In a condenser 80% of the power takes vapour to liquid with no temperature change.

I don't think so, one is a plate the other one a coil.

I'm assuming that the black hose from the bottom of the photo goes to the wall paper stripper, and you measured the power into the stripper with your DVM? What is the heat loss down the black pipe? Does that affect the experiment? (I spent a day proving conservation of energy - getting a total knockdown power measurement to match my element rating. It took a lot of insulation and fiddling.)

Yes, the black hose connects to the wall paper stripper. The paper stripper rating is 2000 Watt and I measured 1700 Watt. So I lost 400 Watt due to the uninsulated reservoir and hose. This was before my SCR arrived, that is one of the reasons I did the experiment in the kitchen instead of the garage to make use of the cooker hood. After a short while it was becoming very humid in my garage.

The pic shows what I think is happening in an offset coiled condenser. You can check this with your trusty thermocouple. A more classic Nixon/Stone condenser is easier to measure than your nice tight one. The vapour comes in the bottom. There is a region where condensation occurs. It is uniformly at the liquid boiling point: any region that is cooler immediately gets heated by vapour. There is a region above that with air in it. The temperature drops quickly in this region. Then above that there is a scrubbie. The well known observation is that the scrubbie effects the condensation. I don't get it, and although its well known, I don't believe it.

More or less pure ethanol vapor is heavier than air, so I think that the hot ethanol molecules have a tendency to to fill the voids created by the condensed vapor. Steam is lighter than air so if a hot water molecule have a clear unrestricted path out of the condenser it will escape as the voids are filled with air. I think that is why the scrubby between the windings of the coil is so effective in this test. I think that putting the scrubby above the coil will only keep the flies away but it something that I will test the next time