My new Liebig.

Anything cooling/condenser related.

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rockystill
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Re: My new Liebig.

Post by rockystill » Wed Sep 05, 2018 7:19 am

Thank you!

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Alchemist75
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Re: My new Liebig.

Post by Alchemist75 » Wed Jan 02, 2019 6:19 pm

heartcut wrote:"High efficiency" lab condensers have a thin cooling medium annulus, so I tried a 19 ft 3/8" inside a 1/2" x 0.035" tube for a wort chiller and I chill 6 gal of beer to pitching temp in less than 10 min with about half the water it took with my 1/4" inside 1/2" cooler. Maybe making the outside of a liebig closer to the inside would have a similar effect?
I've brought this up in a couple threads but it hasn't seemed to get much attention. My observation, using lab equipment, is that the west condenser (a variant of liebig) works drastically better than standard liebigs. Having less space between the jacket and vapor tube DOES make a difference in a noticeable way. This principal has affected the way I build condensers any more. You can get away with rather shorter condensers using the west design. Why this is so I have my theories about but I'm no engineer so I'll leave it to another to say why. I only know it works.
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still_stirrin
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Re: My new Liebig.

Post by still_stirrin » Wed Jan 02, 2019 7:46 pm

Alchemist75 wrote:
heartcut wrote:"High efficiency" lab condensers have a thin cooling medium annulus, so I tried a 19 ft 3/8" inside a 1/2" x 0.035" tube for a wort chiller and I chill 6 gal of beer to pitching temp in less than 10 min with about half the water it took with my 1/4" inside 1/2" cooler. Maybe making the outside of a liebig closer to the inside would have a similar effect?
....I have my theories about but I'm no engineer so I'll leave it to another to say why...
Well, I AM a mechancal engineer. And without getting too deep into the physics (mathmatics) of heat exchanger design, there are a few factors which when considered, will improve efficiency of the condenser.

First, heat is transferred OUT of the vapor through conduction through the walls of the heat exchanger’s vapor tube. The heat conduction is proportional to the surface area...that is, the diameter times the tube length. Yet the heat transfer is inversely proportional to the tube thickness. So, you want a thin wall vapor tube...type M instead of type L or type K (typical for copper tubing).

Also, copper is greater than 10 times better at conducting heat than stainless steel, with thickness being equal. But, often stainless tubing has a thinner wall which helps improve its performance.

Now, heat is transferred from the vapor tube(s) into the coolant fluid...typically water. And the heat is collected in the water through convection. Convective heat transfer is optimized by turbulence to a limit. Too fast of water flow will decrease heat transfer, yet water flow slightly greater than laminar flow will transfer heat best. So, slow flow with a narrow annular flow area will be the most efficient...less pumping power input and greater energy transfered.

Successful heat transfer will raise the water exit temperature nearly to the entry temperature of the vapor inlet. This is why counter flow exhangers are preferred...heat transfer efficiency.

But like the heat mixture in the water jacket, the vapor inside the vapor tube transfers its heat via convection to the wall of the vapor tube(s) (exposure to the walls) at which point conduction pulls the heat through the tube wall(s).

If the length of the heat exchanger has limitations geometrically, you can improve performance by using multiple tubes in a tube bank...a shotgun. Again, conductive heat transfer is proportional to the vapor tube diameter by its length multiplied by the number of tubes.

Also, vapor dwell time in the tube bank is increased as the vapor speed is reduced, allowing the vapor to transfer its heat (and condense) more efficiently. Too fast..and the vapor will puff through without fully condensing. And, increasing the water flow rate or adding ice won’t solve the excessive vapor velocity problem...only reducing the heat input to the boiler will help because you’ll reduce the vapor production/mass throughput.

So, vapor speed is a key factor for condenser design as well.

In summary, features to consider are:
1) vapor tube material,
2) vapor tube surface area (diameter x length),
3) vapor flow velocity,
4) coolant fluid (water) flow rate,
5) coolant flow regime (laminar vs turbulent),
6) counter flow design, and finally
7) the number of vapor tubes in the tube bank.

Kinda’ deep answer, but heat exchanger design is a fundamental course for a mechanical engineer. Sorry it seems so complicated...it’s the physics involved. But hey...at least we don’t have to consider radiative heat transfer here.
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