- --- povinstitute <povinstitute@...> wrote:

> Does anyone have any experience using this type of condenser design

As effective? sure...as efficient? Almost.

> and will it perform as efficiently as a coil occupying the same space?

>

> http://homedistiller.org/detail/STILLHEAD.doc

The efficiency of a condenser is proportional to 4 things:

1) Differential temperature - how much colder is the cooling water than the

vapor it's cooling

2) Flowrate - how much coolant can you push through the coil in a given time

(i.e. liters per hour) which can affect #1

3) Thermal characteristics of the materials used (the coolant and the

condenser)

4) Surface area of the heat transfer surfaces.

To make a valid comparison, on must keep all factors but one constant. So,

assuming we have the first three constant (temp of the water, flowrate of the

water, and materials) then the factor that makes all the difference is the

surface area where the coolant and vapors exchange heat (a 'condenser' is

simply a heat exchanger where a phase change (vapor to liquid) occurs).

The condenser you're referencing is also known as a "cold finger" style, kind

of like a liebig condenser inside out, inside another liebig condenser. The

coolant flows through the outer jacket and back through the center pipe and

finally out through a pipe inside/concentric to that. Effectively, your heat

transfer surfaces are the inner wall of the jacket, and the outer wall of the

"finger" made of the center pipe.

Now, for the math (this is going to be *very* approximate, but it shows the

proportions):

1) We'll assume that we have a outer jacket of 2" and the inner jackect of 1

1/2" (leaving a 1/4" space all around for your water) and the inner "finger" is

1" pipe (the diameter of the outlet in the middle is irrelevant except if it

restricts flow...we'll assume not).

2) We'll also assume that this condenser is a foot long...just 'cuz.

3) the surface area of the outer jacket is 3.14 * 1 1/2" (circumference =

pi*diameter) * 12" ~ 56.5 sq. in.

4) the surface area of the inner pipe is ~ 37.7 sq. in.

5) total heat transfer surface is ~ 95 sq. in. (I'm rounding)

Now a spiral condenser, we'll figure the math like this:

1) We'll assume that we're using 1/4" tubing

2) We'll calculate each revolution of the coil were a separate ring and ignore

the extra area added by the portion that sticks through the wall that supplies

and returns the water...just know that it adds just a little bit more to the

total.

3) Each ring will be ~1 1/2 wide on the outside, but with 1/4" tube, that

means that the hole is 1"...for the sake of a happy medium, we'll assume a 1

1/4" diameter to split the difference.

4) Giving a small (say, 1/8") gap between each ring in the spiral, that allows

for (12" / 3/8" (tube plus gap)) = 32 coils in your spiral.

5) The surface area of each ring is 1/4 * pi (thickness of the tube) times 1

1/4 * pi (diameter of the ring) and equals around 3.1 sq. in.

6) Thus, the total surface area of the coil is 32 * 3.1 or ~ 99 sq.in.

(rounding again).

All told, they're nearly equal...in all honesty, it really left me

reconsidering my next condenser. Furthermore, one could realistically achieve

a much greater flowrate through the cold finger design than the coil, thus one

could maintain a greater differential temperature (less time spent in contact

with the vapor thus heating up) than the coil. The coil's internal size

seriously restricts flow so that the leaving water is quite toasty and at that

point not too effective in condensing.

The remaining consideration for the cold finger design would simply be that of

pressure release. With coil condensers, the top is either open, or at least

vented to protect in the event that heat input should exceed heat removal (i.e.

your pump fails/blows up and stops pumping) or when the heat is turned off, the

rig doesn't implode from the vacuum. The cold finger design as described by

that drawing inherently requires a sealed top...though it could be tweaked to

have a vent.

Very good question,

Trid

-holy crap I'm longwinded - --- In Distillers@yahoogroups.com, Trid <triddlywinks@...> wrote:
>

Standard white table vinegar, it's 5% acetic acid. Use it neat. In

> What's the typical concentration that you use?

>

> Trid

> -humblest apologies for the brain hurty :)

>

Oz we buy cheap homebrand stuff from the supermarkets for about 50

cents per litre. I get 5 x 4lt plastic containers of it about once a

year.

Slainte!

regards Harry