Coolant Water Temp Vs Vapors on takeoff

[theskaz]

Observation:

When my new pot still was doing it's sac run, I was recirculating water through the shotgun condenser. when the temp of the water reached 145 as measured by a digital temp sensor, I started seeing vapors coming out the end. added more cold water to get the temp down to 130, and vapors stopped (as visible to the eye)

Question:

Is there a known Max limit for coolant temps before they no longer work to knock down the vapors irrespective of the type of still or condenser?

[rubelstrudel]

Cooling efficiency and ability is a function of the difference in temperature between product medium and cooling medium + the efficiency of the heat exchanger.

In practical life it is difficult to get efficient cooling when the coolant is above 50c or so depending on the properties of your cooler.

[LWTCS]

Two factors
1. Flow rate for cooling medium
2. Cooling medium temps

If your cooling medium temps are hot, then you need more circulation. Similarly, if your cooling medium temps are cool, then you'll need less flow.

The size of your HX's cooling surface area will factor into how to apply 1 & 2

[theskaz]

Thanks guys. I ask the question for programmatic reasons, lets call it a safety shutoff for the heating elements. If I say "If the coolant temp gets to 120F (~50c) kill or cut heating element power" is there any rebuttal that could be had?

this is from a safety standpoint, not so much an efficiency standpoint.

[LWTCS]

I would definitely run the system manually first to fully determine how all of your input variables shake out during the run.
Change in any of the variables changes that "Alert" function that your trying to achieve based on collection speed/purity etc.
Are you recirculating your cooling medium, using a fresh water supply, chiller?

[Single Malt Yinzer]

I started seeing vapors coming out the end

When you see vapors/puffing it's a really bad sign - alcohol vapors at that temp will flash over with any source of ignition. You did the right thing to cut the heat back.

For closed loop cooling I aim for 2-3x the size of the still for cooling without having to add ice or other cooling measures. It depends on a bunch of factors but also the time you're distilling also plays into it. My setup is such that I can swap warm water with cool water as I am doing the run. It's a pain to deal with but I don't have an automated system. Would be nice though.

[theskaz]

I would definitely run the system manually first to fully determine how all of your input variables shake out during the run.
Change in any of the variables changes that "Alert" function that your trying to achieve based on collection speed/purity etc.
Are you recirculating your cooling medium, using a fresh water supply, chiller?

I definition have and will continue running manually as needed to test. whether or not I am using a chiller, fresh water, or any other device would be outside the scope of my question. all those methods effectively set the water(coolant) at a certain temp when it comes into the condenser. the temp of the water, and it's usefulness of knocking down vapors as a "starting point" is my goal. on my still, i observed about 140F as the tipping point, and rubel says ~50C (~120F). Im curious about other stills.

I started seeing vapors coming out the end

When you see vapors/puffing it's a really bad sign - alcohol vapors at that temp will flash over with any source of ignition. You did the right thing to cut the heat back.

For closed loop cooling I aim for 2-3x the size of the still for cooling without having to add ice or other cooling measures. It depends on a bunch of factors but also the time you're distilling also plays into it. My setup is such that I can swap warm water with cool water as I am doing the run. It's a pain to deal with but I don't have an automated system. Would be nice though.

All great points. and I know vapors are a nono, hence a bit of a safety idea. I was running 5 Gallons of wash and 15 gallons of water recirculating. took 45 minutes from power on till I was done and I had to add some cold water @ the 37 minute mark.

Keep in mind im asking in general, not specifically for my still, or even "my" design. For those that have noticed when their recirculation water isnt doing it's job, what temperature was that at?

[StillerBoy]

I was running 5 Gallons of wash and 15 gallons of water recirculating. took 45 minutes from power on till I was done

From the quote above, I would estimate you have a high power boiler.. but running the cooling system from a 15 gal reservoir, is going to give you problems..

For a unit to run properly, a constant temp water flow is required, otherwise, you will not have an efficience running unit, you will be constantly adjusting for efficiency.. most members who run from a reservoir use a 35 - 45 gal barrel to work from with many having also a cooling system attached to it, thus providing constant stable water temp going to the unit..

The more constant, colder the water is, the better it is to manage efficience of the PC and RC..

Mars

[Fruit Squeezer]

From a safety standpoint,
YOU
are the safety measure....
You should not run any type of still automatically. It invites complacency.
Even worse, DO NOT rely upon any still to run unattended.

Wierd shit can and will happen when permitted !
A hose can pop off or kink, rendering a temp alarm innefective. A vapor leak can occour, creating a flamable vapor cloud, and reducing coolant output temps, rendering an alarm innefective. The column / linearm could clog, creating a pressurized bΩmb, and again, coolant temps would drop as catastrophy loomed.

Example: The explosion at George Jones's distillery.

http://www.wkms.org/post/kentucky-fire- ... n#stream/0" onclick="window.open(this.href);return false;" rel="nofollow

Professional tradesmen built the still and experienced craftsmen were in charge of it. Complacency and reliance upon automation (and blind faith in equipment) led to a horrible end.

My point isn't to bash the idea, but automation is always awesome until it's relied upon and fails horribly.

Forgive me if I came at you strongly, but I am a total safety Nazi. It's just how I am.

[theskaz]

I appreciate everyones input, I really do. You all have great points and my question isnt getting answered.

I wasnt asking from the perspective of my cooling system is broke, and I'm trying to fix it. Nor am I asking about all the other particulars that go into heat dissipation. My simple ask is "What temperature have you guys noticed that the cooling medium is no longer effective" I was expecting answers like
"My still would get vapors @ 140"
"Mine would be getting them @ 120"
"I dont need no stinkin thermometer"

I am trying my damnedest to not be disrespectful, and I apologize if it comes off like that.

@Fruit Squeezer,
you have a point, and let me go on the record that I am not automating anything.... really....

What I am doing, is building a dual controller for my EHERMS brew setup AND my still. This controller has a touch screen that shows temps for my HLT/MLT/Boiler (or Boiler/Column/Coolant) and has buttons to turn things on and off. Now, for that to work, I need certain data, and since I already have that data, why not add some additional safety measures in place that go above and beyond just my 2 eyes? Think of it as an additional indicator that something is out of bounds. I said that I wasn't automating anything (on the still side, I am automating on the brew side) but there is some kind of automation in the fact that when i slide my bar from 100% to 75%, my SSR kicks on and off automatically. and every 750ms, my temp sensors go get a reading. it kinda ends there though. just a 2nd set of eyes per-se. Ill be starting another thread about the particulars when I get my PCB back from the assembler.

[Single Malt Yinzer]

My simple ask is "What temperature have you guys noticed that the cooling medium is no longer effective" I was expecting answers like
"My still would get vapors @ 140"
"Mine would be getting them @ 120"
"I dont need no stinkin thermometer"

The answer is it depends on your setup. If you want a number to watch for use 100. It's arbitrary but should be more than safe.

Factors:
- If your vapor tube is copper it will transfer more heat out of the tube and provide more cooling.
- Stainless steel transfers less heat then copper and reduces the effectiveness of the condenser.
- If your vapor tube is smaller than 1/2" then the speed that vapor travels reduces the ability of the condenser to cool the vapor.
- if the water jacket is 1" and the vapor tube is 1/2" it can heat up the water quickly reducing effectiveness.
- You can stick a SMALL amount of copper mesh in the end of the condenser to reduce the speed that the vapor travels. I don't like this option but many people do it.

And yes we went off topic for this post - sorry. You seem to have a good cooling setup and were asking a valid question. But this is the internet so we ignored it.

[theskaz]

Thank you SO MUCH! that is perfect.

on one of your factors, if you have 5 x 1/2 vapor tubes, the speed isnt an issue right? it would be like going through a 2.5" tube?

... but it's inside a 2" tube... does that math work?

[Single Malt Yinzer]

A shotgun tube condenser like that does 3 things:
- it increases the surface area which makes it more effective (5x as much surface area as 1)
- it decreases the speed the vapor travels (surface area/volume)
- it increases the amount of water in the water jacket so it decrease the speed that it heats up

if you're puffing with a 2" shotgun you're running WAY too hot in the kettle. That type of condenser should be able to handle nearly anything you throw at it. I know we say stripping runs should be hot and fast but not that fast. You should be getting a nice stream the size of a pencil lead. Beyond that any you're going a little crazy.

[ydoih8u]

A=πr²

So the area of a 2 inch tube would be 3.14*(2/2)² = 3.14 inches around. The area of each 1/2 tube would be 3.14*(0.5/2)²= 0.19625 inches times 5 yo get 0.98125 inches around of area for all 5 1/2 tubes.

[rubelstrudel]

A=πr²

So the area of a 2 inch tube would be 3.14*(2/2)² = 3.14 inches around. The area of each 1/2 tube would be 3.14*(0.5/2)²= 0.19625 inches times 5 yo get 0.98125 inches around of area for all 5 1/2 tubes.

I think you should check those mathematics.

Area of a circle is Pi*radius² but that's not really interesting here.
The surface area of a tube: Area(tube) = Pi*2*radius*Length (I.E. circumference * length of tube)

[ydoih8u]

I wasn't giving the surface area of a tube. I was answering the question directly that 5 1/2 tubes equal 2.5 inches of area.

[still_stirrin]

A=πr²

So the area of a 2 inch tube would be 3.14*(2/2)² = 3.14 inches around. The area of each 1/2 tube would be 3.14*(0.5/2)²= 0.19625 inches times 5 yo get 0.98125 inches around of area for all 5 1/2 tubes.

Here, let me help translate what I "think" you're trying to say.

The "flow area" for the vapor, which directly affects vapor velocity, the 1/2 nominal ID (type M) is 0.2543 sq.in. So, 5 nominal vapor tubes is 5 x 0.2543 = 1.2714 sq. in.

Likewise, the flow area of 2" (type M) is 3.1699 sq.in., or roughly 3.1699 / 1.2714 = 2.49 times the vapor flow area.

Now, when calculating the coolant flow area you consider the OD of the vapor tube bank. For this, the OD of the 1/2" (type M) is 0.625" such that the water flow area is 3.1699 - (5 x 0.3068) = 1.6359 sq.in.

That means the ratio of the coolant flow area / vapor flow area is 1.6359 / 1.2714 = 1.287.

But since heat exchanger efficiency considers the conducting surface area, which is the circumference of the vapor tube OD x the number of tubes x the length that the vapor tube is in contact with the coolant medium (the tube bank length in contact with the water), you can't disregard the length of the shotgun (or a simpler design...Liebig).

Also, keep in mind that heat liberation inside the vapor tubes is a function of the dwell time...the direct consequence of vapor velocity. Typically, flow velocities greater than 20 feet per second result in poor heat transfer rates. Slower velocities are better, so increasing vapor flow area is a benefit to efficiency, not only inside the vapor tubes but also in the water jacket because of the increased conducting surface area.

Sorry for the dissertation, but I wanted to help translate the communication that has been bouncing back and forth, to hopefully clear up the misunderstanding.
ss

[theskaz]

A shotgun tube condenser like that does 3 things:
- it increases the surface area which makes it more effective (5x as much surface area as 1)
- it decreases the speed the vapor travels (surface area/volume)
- it increases the amount of water in the water jacket so it decrease the speed that it heats up

if you're puffing with a 2" shotgun you're running WAY too hot in the kettle. That type of condenser should be able to handle nearly anything you throw at it. I know we say stripping runs should be hot and fast but not that fast. You should be getting a nice stream the size of a pencil lead. Beyond that any you're going a little crazy.

in my 2 sac runs, I knocked down everything without an issue (my shotgun condenser is 2ft long) and got about just a tad larger than a pencil lead. I have a 5500w element in the boiler and was running it at 100%. the pump that was recirculating was a chugger pump (7GPM) through 1/2 in lines. once the coolant temp got to 140-145 it started puffing. I just added cold water, and it was ok. that reminds me though...

I had an interesting thing happen. after I added cold water and it cooled the condenser down, the distilllate was dripping but erradically. it was puffing(audibly) until i closed the coolant valve to almost closed. then i got the normal stream. If i opened it back up, puffing again. I smelled and tasted the product and it was pretty much water. I was trying to find the cardboard and wet dog, and never caught it.

[still_stirrin]

...I had an interesting thing happen...after I added cold water and it cooled the condenser down, the distillate was dripping but erratically....it was puffing (audibly) until i closed the coolant valve to almost closed...then i got the normal stream. If i opened it back up, (it started) puffing again.

When you started recirculating cold water, the vapor was collapsing in the vapor inlet, such that it was literally "sucking" air into the condenser. This is type of flow is called, "huffing" obviously because it is sucking in air from the spout.

The opposite flow, but with the same sounds, is "puffing", when vapor is being exhausted out of the spout due to inadequate cooling power. You experienced this when your reservoir water warmed to 140*F, or more.

If your reservoir warms too much during the run, you either need a larger reservoir, or you need to "turn over" some of the coolant in the reservoir. If you can drain some of the reservoir water and refill it with cold, or cool water, you'll see the product output stability more constant throughout the run.

It is obvious that your shotgun condenser is doing its job well, just that you aren't removing the waste heat in the reservoir in time.

...I smelled and tasted the product and it was pretty much water. I was trying to find the cardboard and wet dog, and never caught it.

If you've successfully refluxed the wash, chances are the backend is compressed as well, and the purity will drop very rapidly once the alcohol has been exhausted. I find that I don't get much "tails" when I use the VM reflux still. The %ABV will drop very sharply at the end just as the output flow diminishes to a drip.
ss

[theskaz]

no reflux'n just a straight pot still.