What makes a good condenser

[froglet]

Hello please be gentle with me! I have had a big search around, and read our books and things but I still have to ask...

In an inline reflux still, is there a way of calculating how much copper tube is the optimum amount to use in your condenser?

We want to build our condenser with a tightly wound 'double helix' style coil to pump the water through, to increase the surface area for the vapour to make contact with.

However we dont want to go overboard and build a condenser that is a million miles long. We just want to make sure the one we build will handle Froggy's pride and joy - the 2400W heating element. And not just handle it, but work well!

The closest I came to having any real joy was the 'wee calculator' on the parent site, in the condensers section. But it seems to deal mainly with worm style condensers and liebig ones.

Can someone point me in the right direction? Even if the calculations are very complicated I'd like to have a go at working it all out.

[HookLine]

1. The condenser does not have to deal with the full 2400 w. In a 2.5" column it only needs to deal with maybe 1800-2000 w. You don't run a reflux column flat out.

2. I don't know of any calculator specifically for reflux coil condensers. The numbers the calculator on the home site gives don't make sense to me. Ignore it.

3. If you have water restrictions and are going to use a re-circulating pump and reservoir set-up to push water through the condenser (instead of taking it straight from the tap), then you can't use the standard double helix type coil. They have too much back pressure for most pumps. One possible way around this is to use a bleed valve on the output side of the pump, before the coil, and bleed some of the pump output flow straight back into the reservoir so the back pressure is reduced down to a level the pump can cope with. Otherwise you need to use two (or more) parallel coils.

(BTW, strictly speaking, what is referred to by home distillers as a 'double helix', is not. Look up double helix on wikipedia. The so called double helix condenser is probably more accurately described as a single-path, double concentric counter-wind. )

4. For a double coil condenser in a 2" column, I use about 10' (3m) of 1/4" copper tube. It gives an overall condenser length of around 7" (not including connection tails). This easily copes with the power levels I use, around 1200 w. If you use maybe 5 m of tube that should be plenty. You also shouldn't need to make it longer than about 8", cause there will be plenty of extra condenser tube (surface area) in the increased diameter of the coils.

5. Leave some space between the successive winds on each coil, don't have them touching, let the vapour flow around the whole tube.

6. Make sure you use annealed, thick walled tube, the stuff the air-con guys use.

[SaltUbar]

Hi there,

I have had the same problems trying to calculate how much copper I need to extract the energy at the top of the still

q = k A dT

Thermal Conductivity (k) Heat Cap (J/g x C)
Ethonal = 2.44
Copper = 401 0.39
Water = 0.58 4.187
Air = 0.024
Foam = 0.033

W/(m C) 1 = 0.85984 kcal/(hr m C)

q = k A dT / s         (1)

where

q = heat transferred per unit time (W, Btu/hr)

A = heat transfer area (m2, ft2)

k = thermal conductivity of the material (W/m.K or W/m oC, Btu/(hr oF ft2/ft))

dT = temperature difference across the material (K or oC, oF)

s = material thickness (m, ft)

q = 2 π k (to - ti) / ln(ro/ri)  


from what I have been able to gather from research. The heat (energy) transfer is aproximated by the same as the surface area of a flat plate so if you can calculate the surfac area of the copper piping that is in contact with the distallate and cooling water then it should be very close to the performance of your condensor.

Further you have to make aproximations of the heat capacity (conductivity) of the substances as the total is a summation of the capacities.

This turned out to be way complex and I didnt want to spend the effort, i opted instead to take the advice of others on here and made a condensor with aproximate charactoristics as suggested.
See below my first attempt at a cold finger with a double helix condensor

Hope this helps
regards

[HookLine]

That should do it.

Pretty good for a first attempt.

Got a vent hole in the top of the cap?

[Igor_From_Jdessa]

My old experiments. Click for enlarge image

[myerfire]

Nice pictures and nice work. I'm envious.
myerfire

[HookLine]

+ 1

Particularly like the bending work at the bottom of the coil (first pic), where it does a 180º. That is very clean.

And how come they are blue? Something wrong with the camera?

[Igor_From_Jdessa]

I bent a pipe 6x1mm with hands on the polypropylene pipe d20mm. Blue color is given by a flash. A camera is a telephone of NOKIA E66. IMHO not bad for a telephone.

[FloridaShine]

Someone on this site had a great tutorial making the double Helix coil, I found the winding.doc, this is good, but the other one was using 0ne inch black pipe with 3 Toggle eye bolts in line to hold tubing
The one inch pipe was mounted with 2 pillow blocks, Then you bend the first coil starting at about 90 deg, then using a spring bender you continue to wrap the coil forward. until you reach the right length,
Then he would wrap paper around the coil and secure with tie wraps to begin the outer coil. For the life of me I can no longer find this, I did save one of the images, If any
one recognizes the coil please send me link to get all the instructions,

[Samohon]

Here is the Link...

It could be found in the New distiller Reading Lounge..,

Welcome to HD...