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# Vapor Speed and Watt Density per Liter

edited April 2016

my new setup with a 150L boiler and three elements will have 2ea 5500 low density (one of which will have the power controller on it) and 1ea 4500w low density element. probably massive overkill for a 4" column but whatever. My watt input per liter has halved from the current 9000 watts over an actual 40 liter charge (with heat up of about 18-20 min), to a 14500 watts over an estimated probable 125liter charge (heat up times estimated 35 minutes). what will that do to my vapor speed/volume thru my 4" 7 plate column?

watt density currently is close to 225w per liter. new system is close to 120w/liter. does my watt density effect vapor speed/volume or just heat-up time?

Tagged:

• Watts affect vapour speed, density effects scorching. Eg." X "watts at low density gives the same vapour speed as "X" watts at high density. The lower the density the less chance of scorching

• edited April 2016

Ultra low watt density heaters will not prevent scorching, the sheath temperature and watt density is still astronomical compared indirect heating methods (bain marie, oil jacket, steam jacket, etc).

However, running multiple ULWD heaters at fractional power will make a difference.

Typical watt densities for these I see referenced is about 30-50w/sq.in.

Doubling the needed elements and running at 50% max brings this down to 15-25.

Low watt density would really be considered about 5-10w/ sq.in. However, this doesn't change the issue of high sheath temperature.

• Let's assume you have heated up your boiler to the point where you are producing vapor. We know that more heat input equals a quicker time to boiling for a given mass of liquid. Once you reach the boiling point (saturation temperature) then the physics are that your heat input goes to losses to the environment, and evaporation of product. The amount of heat that you lose to the environment will likely be slightly higher for a larger boiler, but should be small in comparison to the heat that goes into producing vapor.

Lets assume that you lose 500 watts to the environment. At this point the vapor produced is proportional to the heat input. Therefore if you double the heat input, you will double the volume of vapor produced and therefore double your vapor speed. You can now see that having twice the volume of liquid in the still really does not enter the equation once you are at saturation temperature or boiling.

• @grim. Agreed ulwd elements generally dont prevent socorching how ever multiple elements on controller reduce the effects. Was answering in regards to vapour speed

• edited April 2016

Yeah just always bugged me that everyone referred to them (including the manufacturer) as ultra low watt density, which they are, for water heaters, but for our purposes, and in the grand scheme of things, they are "Very High Watt Density" elements, which are only marginally better than "Extremely High Watt Density" elements, and they still have sheath temperatures only slightly cooler than the surface of the sun.

:)

Has nothing to do with the topic, of course.

@Lockie summed it up perfectly.

• edited April 2016

@grim said: grand scheme of things, they are "Very High Watt Density" elements, which are only marginally better than "Extremely High Watt Density" elements, and they still have sheath temperatures only slightly cooler than the surface of the sun.

Lmfao.

• In any case 14.5kw is going to be much more than a 4" column can handle, so you will have no problem getting the maximum potential from your rig, even assuming Procaps.

StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

• I'm only using sugar and juice washes at this point so scorching isn't a problem. I do notice that the higher density elements give me more foaming from cavitation produced, particularly during stripping.

Ok. Well it's good to know I've got the power to run the boiler and will maintain my column capacity as well.

I'm gonna play with my plate combos too. I'm running 3 pro caps and 4 perfs now. I want to switch to the SD perfs and add rashig rings to 2-3 plates.

Question is... Will adding rings ON TOP of plates keep my plate reflux and add the reflux from the rings to it? IOW if 12" of rings gives 2.3 plate equivalent does that get added to the plate equivalent of the actual plates?

Also am I correct in my understanding that by adding plates I reduce the need for reflux condensation and this can speed up production at higher ABV? Basically more plates is faster fuel?

• Also I should say you guys are friggin legendary. Thanks for the responses!! Big help.

• I seem to recall someone saying they got flooding with packing directly on top of the 4" sieve plates. Not positive but it rings a bell.

StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

• That would make sense if the packing got in the down comer and slows the flow.

• in a place with dual voltage, I would look into powering you HV elements on the LV, if you are in the US and have 240/120, powering a HV element on the LV, halving the voltage reduces the power to 1/4.. this takes multiple contactors and safety items to implement properly.

Or, anywhere, you could make a jumper cord/box for two elements that plugs into a single HV outet (run two (or more) elements in series... 2 5500 elements in series will be 2750W, you can most certainly run this on a single controller, and if you stay under 50%... add a 3rd and 4th element in series along side the first two for a series/parallel combo, and back at 5500W at 1/4 of the watt density...

and remember, reducing watt density is to stop scorching, not foaming... foaming will happen, and slow heating, a rolling boil, circulation,additives, etc are how to combat that.

• edited May 2016

@CothermanDistilling said: Or, anywhere, you could make a jumper cord/box for two elements that plugs into a single HV outet (run two (or more) elements in series.

I suggested this a while back and got told it was over complicating things. It might be a bit of stuffing around to wire up but its actually pretty simple inside and means you can do a lot without ever needing a controller.
I had a look back then to see what combos I could come up with by using a few elements and combinations of series and parallel wiring. Mixing element sizes gives you even more possible steps.
The finished box could be as simple as a power board with a jumper lead that you insert into different plugs for different power levels. No switches, no relays, no controllers just wiring.
Three equal sized elements sized for the boiler/column size looks like a good choice to me. Lots of steps in the 'run' range and two major steps in the 'heat up' range. 3x 2.2kW elements that I use would be a good size for 2" and under I think.

Hooking elements up like this will change their Watt density but not in all combo's unfortunately.

• I think they talk about that in Mike Nixons book

• They do indead. The only book you need.

• @punkin said: I seem to recall someone saying they got flooding with packing directly on top of the 4" sieve plates. Not positive but it rings a bell.

That was me using stainless steel packing

Worked it out to be a few different things

Stainless was packed too tight for the seive plates

Super RC was cooling too much so knocked too much back down to fast relevant to vapour speed. If I had reduced coolent flow and power I could have reduced the impact

The flow controllers I had on my procaps where not allowing my caps to drain correctly

• If you have downcomer flow issues with procaps, something definitely wrong!

• You can test the maximum flow rate through the procaps in your column just by pouring in water at the top of the column until you get to a flow rate where the plates flood. I expect that flow rate to be high. Obviously this is a static test with no power applied to the boiler.

Adding packing on top of the plates is a way to increase the purity of the product from plates that are not correctly designed for the operating conditions of the column. This does not mean there is anything wrong with the plates - it could be the way that you are operating them, is not what they were designed for.

This does not however mean that there will be a corresponding increase in product speed. You could get higher purity at the same speed as previously. Lots of variables involved.

• maybe with a sealed boiler and pouring in, but that is not normal still operation... and that is not 'flow restriction' but instead 'vapor lock'...

• edited June 2016

@Myles said: You can test the maximum flow rate through the procaps in your column just by pouring in water at the top of the column until you get to a flow rate where the plates flood. I expect that flow rate to be high. Obviously this is a static test with no power applied to the boiler.

Adding packing on top of the plates is a way to increase the purity of the product from plates that are not correctly designed for the operating conditions of the column. This does not mean there is anything wrong with the plates - it could be the way that you are operating them, is not what they were designed for.

This does not however mean that there will be a corresponding increase in product speed. You could get higher purity at the same speed as previously. Lots of variables involved.

I don't believe this to be true. A packed section will take the place of more plates in a shorter length is all. Adding a packed section is done in a a column without any plates to increase purity.

StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

• edited June 2016

Sorry @punkin, but adding packing on top of plates in a plated column is a fairly conventional fix in commercial applications.

Normally used when you have changed an operating parameter, or are utilising a column that was actually designed for a different process (or was just designed incorrectly).

It is a fix for a problem, and not a recommended practice, and is a different application to adding in a packed section to an existing plated column when you wish to run a different product.

• Sorry i misunderstood what you were saying.

StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

• @punkin , @Fiji_Spirits , actually punkin reading Fiji's comment again possibly it was my miss-understanding. I read it to mean adding packing inside the column on top of each plate, and not adding a packed column above the plated section.

Two very different scenarios, so perhaps Fiji can clarify which he was refering to?