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Reflux condenser capacity

Reflux condenser capacity

Postby myles » Fri Jul 05, 2013 4:44 am

I am building a new reflux condenser and this time I am going for a variation of Harry's Crossflow.

Horizontal offset tube in shell. I am using 19 of 8mm tubes, and have the end plates ready.

condenser ends.png


These discs are the right size to fit inside the shell, they will get brazed in place first with 56% silver solder, then the tubes will be soft soldered in. The top set are actually for a 7 x 12mm product condenser, both condensers have a 54mm / 2" shell.

I usually use the default settings on the condenser calculator on the HD home site, and build the reflux condenser to full power capacity. For this reflux condenser that will be 19 x 8mm x 300mm for 5.7 kW (6 kW element).

However I suspect this is over spec. (As it is this design I could easily shorten it without any fuss.) Let's face it there are going to be losses from both the boiler and the column, also how often do you ever stabilise on 100% boiler capacity?

So I am curious what you folks do. Do you downsize your reflux condenser by 20%, 30%, 50% even, or do you build for 100% boiler input?
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Re: Reflux condenser capacity

Postby midcarolina » Fri Jul 05, 2013 5:59 am

Myles........ I have long thought that calc may be a good place to start but may not be all that accurate......... because the vapors we are condensing does not represent the total energy input on the boiler, I think it is just a portion and is really lost energy of the input heat
It seems to me for that calc to be any where near correct we would have to be trying to defeat all the energy input in the boiler. I think condenser efficiency and cooling water temp is much more of a concern of ours

I think to be really accurate someone would have to figure the cubic ft of vapor we are trying to change the state of.....

most calc's you find dealing with heat transfer of say tube in shell condensers are based on enhanced tubes in the condenser
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Re: Reflux condenser capacity

Postby Googe » Fri Jul 05, 2013 11:03 pm

Nice work so far :handgestures-thumbupright: . I find it hard to know my heat input cause I'm on gas, but from seeing what outputs and size condenser other people use I get a bit of an idea. I like to be safe and try to build bigger than needed with condensers. What still is this one going on? .
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Re: Reflux condenser capacity

Postby myles » Sat Jul 06, 2013 8:51 am

The reflux condenser is for a 3" SPP packed vodka column that is thumper mounted. The product shotgun is for the pot still that feeds the column. Because we changed spec mid build to a 6 kW boiler (it would have been a 3 kW) the original product condenser is now not enough, but it should be OK for the column.

Basically it is this:

MN 1.png


Most of the time the pot still will be in use, but there is an option to switch off the product condenser cooling and divert the vapour into the vodka column instead.
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Re: Reflux condenser capacity

Postby Googe » Sat Jul 06, 2013 4:13 pm

Nice mate, so you've got a straight pot, a pot into a thumper than into the packed section, and a pot in the packed column as well, to use with the thumper?.
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Re: Reflux condenser capacity

Postby myles » Sat Jul 06, 2013 5:49 pm

Could do, but it seems the owner will intends to leave the column on the thumper so he can switch from pot still to reflux column with just the use of a couple of valves. 1 in the vapour path and 1 or 2 in the coolant supply. No need to interfere with the tri clamps / gaskets unless he wishes to move things. It just makes storage less of an issue.

You can back flush the packing by putting water in through the heads removal side on the LM part of the column, and I recommend doing a steam clean with just water in the boiler if the column is not going to be used for a bit. I will probably fit a spray ball into the big boiler for ease of cleaning.
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Re: Reflux condenser capacity

Postby midwest shiner » Sun Jul 07, 2013 2:34 am

Once again I am blow away by your creative style of thinking and your superior building skills. Looks badass Myles, keep up the great work.
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