- peter_vcb wrote:

Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

MIKE N- could you please comment on Johans 1/2" copper tube still.

95% from a 3% wash with no packing, what is going on there! all i can consider is that the tube is so narrow that the vapour is exposed to a large surface area just like packing.=============================Hi Peter,I'll give it a go, but first thanks to Johan for the pic. Helps a lot, so I've shoved it in here as wellRodmac is right ... with those indentations it's reminiscent of a Vigreux condenser that has its internal surface area increased by lots of indentations.As I see it, the main feature of Johan's procedure is that it is deliberately kept very slow, so the vapor is moving up this column at a very low speed indeed. As in a lyne arm, vapor will condense on the walls and some of this liquid will be re-evaporated to give vapor with a higher concentration of volatiles. Stripped liquid will accumulate and trickle back down, and the richer vapor will condense a little further up to repeat the process. As the vapor speed is very low, we can think of the column in Tony's terms as having a very small HETP, so we can envisage this liquid/vapor interchange being repeated many, many times before the vapor reaches the top, resulting in good separation.The low speed of the vapor is one important factor. The other is the surface/volume ratio. Same reasoning that we use with packing ... the greater the surface area of the liquid in a given volume of vapor, then the more efficient the evaporation interchange will be. Now the ratio between the internal surface area of a tube and its volume (which will be the same thing as liquid surface area/vapor volume) is very simple: it's 4/D, where D is the diameter. Other things like length and Pi all cancel out. Johan is using 1/2" diameter tubing, so the ratio is 8. Compare this with, say, a 2" diameter tube where the ratio is just 2. He has also increased this ratio slightly by getting busy with his trusty Thor's Hammer, so the ratio could possibly be nearer 9 than 8. We can also see that if he had used 1/4" diameter tubing them the ratio would be up to 16.I reckon that it is this combination of slow vapor speed and fairly high surface/volume ratio that makes Johan's method work so well. I would also think that using several 1/4" diameter tubes would be even better ... the surface/volume ratio would remain the same of course (16), but the volume being processed would increase with every extra tube used. However, if anyone cares to see is this works, I wouldn't bother with the indentations. They are a good idea with 1/2" tubing, but the slight increase in surface area you would get with 1/4" diameter wouldn't be worth mangling a bunch of nice copper tubing that could be used for other purposes at another time.Make any sense?Mike N - I agree that heatloss probably is a problem, but insulate it may not be so

hard since it is a coil.

Johan

Peter, what you are describing begins to sound a lot like a gas

chromatography column, which is often a very long coil of very fine

tubing.

The key problem I see with what you describe will be heat loss - the

smaller the column diameter, the faster the heat loss per unit

length, so there will be a maximum length you can run - as soon as

the column temperature falls below 78 deg C, you're hosed....

You're right that you would have more potential area for reflux, and

that it should proceed downward more slowly, but it will also only

coat a fraction of the tube diameter.

In short, worthy of an experiment!

Mike McCaw

--- In Distillers@yahoogroups.com, "peter_vcb"

<viciousblackout@y...> wrote:> Mike,

length

> yep i was working the same way using mm and using a standard

> of 1m.

or

> so do you think Johans coiled copper tube idea would work as well

> even better? if coiled the cooled vapour will flow down the tube

may

> whereas if it is vertical it may fall straight down and the tube

> experience less wetting of the available surface. conversely it

will

> only flow on the lower section of the tube so vertical may be

better.

> if a coiled one would work it would easier to use indoors you

could

> have 10metres coiled to a low height. it could coil up fully

i

> insulated and coil back down over itself with a fan blowing on it.

> still have this idea of a nice efficient radiator in my room

pumping

> out booze all day and keeping me warm :-)

to

>

> if it scaled up perfectly (i know it wont) a 2" column would need

> be 6m high to work the same as the 1/2" 1.5m column. the cross

to

> section area of a 2" column is 16 times that of a 1/2" column. so

> run at the same power i would need 16 columns at 1.5m which is 24m

of

> 1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so

has

> anybody heard of a very high column run with no scrubbers? cheaper

very

> than copper of s/s would be scaffolding poles. you could get 6m

> cheap and redistill the output to leave the nasties behind.

(?)

>

> Peter

>

>

> --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:

> > peter_vcb wrote:

> > Subject: [Distillers] Re: Reflux Valve = Temperature Controller

> >

i

> > hi Mike

> > makes lots of sense, thanks. i did an excel file after i posted

> yesterday to see the variance in the ratio just like you mention.

> > got different ratios than you (i used mm) .....

is

> > ============================

> > Hi Peter,

> > The way I figured it, the circumference of a cylinder diameter D

> (Pi)D, so the surface area is(Pi)DL

D2L ....

> > The volume of that cylinder is (Pi)D2L/4

> > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)

> or 4/D

number

> > Snag is, the dimensions of this are "per length" so yes, the

> you get will indeed depend on what units you use, so it's better

to

> get rid of that length by comparing different tubes to get a

diameter

> dimensionless number.

> >

> > So if we compare tube A with diameter Da with tube B with

> Db we get TubeA/Tube B = Db/Da

is

> > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches

> diameter, we get Db/Da = 2*4 = 8

> > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B

> 2 * 25.4 mm diameter, and the ratio is again 8.

than

> > In words, Tube A has 8 times as much surface area per volume

> tube B

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> >

> > Better?

> > Mike N

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