Cooling loop w/ passive pump failover protection (pic)

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Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sat Nov 14, 2015 12:52 am

Hi here's a scan of a quick scribble I did of what I have in mind for my cooling loop. If you all could take a look and critique it I'd appreciate it.

A 5A battery maintainer plugged into the wall keeps a 12V 35AH SLA battery charged, a 12V 1A 600 L/hr pump feeds a manifold, branching off the manifold are ball valves controlling the flow to the reflux and product condensers, hot water comes off the condensers into an exterior series of ladder-step hotwater baseboard finned tube that's enclosed in a 4' wide by 6' high by 5" deep "chimney" so the stack effect will draw air up and through the finned tube without the use of fans.

The bottom two steps are bare copper tube wrapped in cotton or burlap with soaker hoses zip tied to their tops to get the coolant down below ambient on hot days. The air being drawn up by the hotter finned tube above it helps evaporate the water in the cotton and the cooled humidified air is drawn up the chimney also helping cool the coolant below ambient. The coolant then returns to the reservoir. The inlet of the radiator needs to be NO LESS than 1 foot above the top of the reflux condenser or it won't flow right.

Note, the stair-step arrangement is actually TERRIBLE for thermosiphon but I can't find a source for longitudinal finned tube whose arrangement can be seen in the lower right corner of the jpg. Since I'm stuck using the regular fin tube I'm using the ladder arrangement but I'm keeping everything sloped at least 30 degrees. To reduce pipe friction as much as I can I'm using 1" pipe and hose all throughout. Reducing pipe friction is also the reason for using shotgun condensers. I'm not quite sure if the ladder-step arrangement will work for passive thermosiphon flow. I might just manually solder up my own longitudinally finned tube - which would be a huge pain in the ass.

Failover; in normal operation the coolant goes 'round and 'round normally using the pump, the back pressure from the pump keeps the check valves closed. If the pump fails the check valves open and coolant begins to flow via thermospiphon (as long as there isn't a big air bubble in the top of the pipe). The control ball valves are bypassed because they'll be heavily restricted from throttling down the much greater pump pressure, far too much for the passive thermo flow to work. It'll probably mess up the run but at least the column wont overheat.
To control flow in thermosiphon mode; the (normally closed) ball valve is opened, upper check valve is clamped off, lower check valve bypass is clamped off, and control ball valves readjusted to whats needed for proper reflux and product takeoff. Because of all the restrictions backflow through the pump and reservoir should be minimal.

BTW, the "flow restrictor" bypass is there to provide at least a little bit of flow through the pump if the control valves are ever completely shut so the pump doesn't overheat.

The above is more for a pump failure scenario, but it should also work in a long term power-out. The 35AH battery not only powers the pump but its the power for all the digital thermometers, relays, and other things I'll have going, it alone should let me finish a run if the power stays off.

Thoughts?

Thanks!

Edit: Fixed diode direction in drawing
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Last edited by FuelMaker on Sat Nov 14, 2015 11:42 am, edited 2 times in total.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by pfshine » Sat Nov 14, 2015 1:06 am

Wtf is that drawing? It makes no sense.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Monkeyman88 » Sat Nov 14, 2015 1:30 am

pfshine wrote:Wtf is that drawing? It makes no sense.
It makes perfect sense. Follow the flow. Simple.

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Monkeyman88 » Sat Nov 14, 2015 1:32 am

FuelMaker wrote:Hi here's a scan of a quick scribble I did of what I have in mind for my cooling loop. If you all could take a look and critique it I'd appreciate it.

A 5A battery maintainer plugged into the wall keeps a 12V 35AH SLA battery charged, a 12V 1A 600 L/hr pump feeds a manifold, branching off the manifold are ball valves controlling the flow to the reflux and product condensers, hot water comes off the condensers into an exterior series of ladder-step hotwater baseboard finned tube that's enclosed in a 4' wide by 6' high by 5" deep "chimney" so the stack effect will draw air up and through the finned tube without the use of fans.

The bottom two steps are bare copper tube wrapped in cotton or burlap with soaker hoses zip tied to their tops to get the coolant down below ambient on hot days. The air being drawn up by the hotter finned tube above it helps evaporate the water in the cotton and the cooled humidified air is drawn up the chimney also helping cool the coolant below ambient. The coolant then returns to the reservoir. The inlet of the radiator needs to be NO LESS than 1 foot above the top of the reflux condenser or it won't flow right.

Note, the stair-step arrangement is actually TERRIBLE for thermosiphon but I can't find a source for longitudinal finned tube whose arrangement can be seen in the lower right corner of the jpg. Since I'm stuck using the regular fin tube I'm using the ladder arrangement but I'm keeping everything sloped at least 30 degrees. To reduce pipe friction as much as I can I'm using 1" pipe and hose all throughout. Reducing pipe friction is also the reason for using shotgun condensers. I'm not quite sure if the ladder-step arrangement will work for passive thermosiphon flow. I might just manually solder up my own longitudinally finned tube - which would be a huge pain in the ass.

Failover; in normal operation the coolant goes 'round and 'round normally using the pump, the back pressure from the pump keeps the check valves closed. If the pump fails the check valves open and coolant begins to flow via thermospiphon (as long as there isn't a big air bubble in the top of the pipe). The control ball valves are bypassed because they'll be heavily restricted from throttling down the much greater pump pressure, far too much for the passive thermo flow to work. It'll probably mess up the run but at least the column wont overheat.
To control flow in thermosiphon mode; the (normally closed) ball valve is opened, upper check valve is clamped off, lower check valve bypass is clamped off, and control ball valves readjusted to whats needed for proper reflux and product takeoff. Because of all the restrictions backflow through the pump and reservoir should be minimal.

BTW, the "flow restrictor" bypass is there to provide at least a little bit of flow through the pump if the control valves are ever completely shut so the pump doesn't overheat.

The above is more for a pump failure scenario, but it should also work in a long term power-out. The 35AH battery not only powers the pump but its the power for all the digital thermometers, relays, and other things I'll have going, it alone should let me finish a run if the power stays off.

Thoughts?

Thanks!
Looks good. But why the check valves?
Why not just have it go, pump, condensers, cooling tower, reservoir, repeat?

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Yummyrum » Sat Nov 14, 2015 1:42 am

Monkeyman88 wrote:
pfshine wrote:Wtf is that drawing? It makes no sense.
It makes perfect sense. Follow the flow. Simple.
yup :thumbup: .....Must be an electronics dude ...diode for check valve .

But...think PC might need cold in the other end :silent:

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by skow69 » Sat Nov 14, 2015 2:14 am

Your diodes are forward biased. Looks to me like all you're going to do is pump water through the check valves and into the reservoir.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by pfshine » Sat Nov 14, 2015 2:42 am

Retracted. For some reason thought it was a still diagram. Looked again and see that while it will work kinda maybe, There is a lot of unneeded pipe and valves and no valves where they should be. I run on my phone so I can't really point out and fix anything on it. But I will try to do something tomorrow. Again sorry about the first post for some reason I thought it was a vapor path of some kind.
Last edited by pfshine on Sat Nov 14, 2015 2:56 am, edited 1 time in total.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Yummyrum » Sat Nov 14, 2015 4:13 am

skow69 wrote:Your diodes are forward biased. Looks to me like all you're going to do is pump water through the check valves and into the reservoir.
skow69...LOL ...yeah I'm agreeing with you here , God damn conventional current flow and them symbols ..that's the way i saw it too and thought it was a cunning way to divert excess water flow around the condensers to keep the pump happy :thumbup: ...then I thought about electron current flow :crazy: ..and stopped thinking about it :wave:

pfshine ... :relaxed: :thumbup:

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Danespirit » Sat Nov 14, 2015 5:04 am

Yes in a electrical circuit it would be diodes.. :)
Now..as i see it the ballvalve for the refluxcondensor , also opens a path to the checkvalve..thus a path direct to your 5 gallon reservoir.
However, you painted the waterflow the other way around, so i assume the checkvalve will be closed in the direction of the reservoir..??
Why do the piping and the checkvalves in the first place..?
You could do with two ballvalves and a bleed off valve (flowrestrictor). :idea:
It will still give you the option of reducing the flow to the RC and maintaining the flow to the PC simultaniously.
The flowrestrictor would only be necessary IF your pump delivers considerably more output, than the piping can take care of (f.ex. a fully closed path to the RC and only partly open path to the PC).
In real conditions it shouldn't be likely to happen.

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by still_stirrin » Sat Nov 14, 2015 6:34 am

I don't think you need the flow restrictor either...most centrifugal pumps can "dead head" without consequence. That is, you can run them with the outlet closed without problem. But...you don't want to run them "dry"...without water. That will burn them up.

I also don't see the benefit of the check valves. I believe the water will flow to the path of least resistance, and the return to reservoir appears to be that path.

I think you can simplify your closed loop circulation system a lot and get the same, if not better results.

Oh, and here's another tip....put your condenser water control valves on the discharge side of the condensers....that way the water tubes will always be full (and pressurized). It will help with the heat transfer.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by shadylane » Sat Nov 14, 2015 7:23 am

I must be missing something, It looks like without the pump running, the water drains back into the 5 gallon reservoir

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by RevSpaminator » Sat Nov 14, 2015 7:37 am

That looks like a lot of rigging. Couldn't you just set up a water flow sensor to cut the source of heat if the coolant flow fails? That would catch a variety of problems beyond simple pump failure.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sat Nov 14, 2015 9:15 am

Thanks for the replies! Appreciate it. Yeah, I'm an electronics guy not a plumbing guy and I put the damn symbols in the wrong way, I'll go fix it... don't know the symbols for a plumbing check valve and the diode symbol is what came to mind.

The thought was that the pressure from the pump would keep the check valves closed, but as soon as the pump quit the backpressure would stop and allow coolant to flow through the loop because of the (small) pressure provided by the now-cooled water coming from the radiator.

I could rig a cutoff valve to the gas flow triggered by a flow switch - and I considered that. But I wanted to have the option to run my still without having to use any external power in a very long term power out situation. I might need to make fuel for chainsaws or something if the windstorm/icestorm/earthquake is bad enough to knock power out for a real long time.

I also considered relying on a solar panel recharging the battery, but I live in the pacific northwest - there isn't much sun in the winter monsoon season. We have a strange climate here, it's either dry as a bone during the summer or wet as hell in the winter. I call it our drown/drought climate.

The coolant wont drain back because its not vented at the top of the loop and there's no point for air to get in, and because the coolant inlets & outlets terminate below the surface of the coolant air can't work its way in from there either.

The pump I have is rated for 9 feet of head so it's not all that powerful, I was concerned about it overheating though without any water going through it if I ever stalled out the flow by accident & closed both control valves.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by still_stirrin » Sat Nov 14, 2015 10:18 am

FuelMaker wrote:...I'm an electronics guy not a plumbing guy and I put the damn symbols in the wrong way, I'll go fix it... don't know the symbols for a plumbing check valve and the diode symbol is what came to mind. outlets terminate below the surface of the coolant air can't work its way in from there either....
You sparky's....a long standing debate about current flow (electrons) from - to + ...that's why you put the diodes in backwards! But I've got to admit, your schematic threw me for a loop with those initially shown backwards (against the direction of your arrows). :shock:

I still think you could save a lot of cost and complexity with the (attempt at a) bypass circuit. It simply doesn't need to be there. Return your air-cooled water to the reservoir and pump to a Tee split for your two condensers. Remember, the product condenser is inlet at the product discharge end and the reflux condenser is inlet at the top (away from the vapor inlet). Put the respective flow control valves on the discharge side(s) of the condensers' water piping for best results.

And if you're worried about the recirculation through the pump, put a Tee at the inlet and one at the outlet of the pump and put another ball valve inline between the two Tees. The water will follow the path of least resistance and when that valve is full open, the water will flow from outlet to inlet of the pump in a continuous loop. Very little, if any water will pump to the rest of the circuit. Closing that bypass valve will drive the circulation water to and through your condensers, depending on the valve settings for each of those.

Stated again....for a centrifugal pump (which I would assume you have), a water "dead head"...ie - closed circuit valves (without a bypass) would not hurt the pump.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sat Nov 14, 2015 11:30 am

Thanks SS, I'll probably delete the bypass then, it'll simplify the plumbing a bit. I'll give some thought to your other ideas. But if I put the valves on the outlet side I wont be able to have it failover to passive thermosiphon flow if the pump fails, it'll be too restrictive. hmmm

It might work if I rejigger the flows so all the automatic thermo flow happens on the condenser outlet sides.... lemme go scribble for a bit.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sat Nov 14, 2015 11:40 am

Yummyrum wrote: But...think PC might need cold in the other end :silent:
Oops, yeah you're right. At that point the vapor is coming DOWN and not up. Good catch. I'll go fix it.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by skow69 » Sat Nov 14, 2015 12:39 pm

still_stirrin wrote: You sparky's....a long standing debate about current flow (electrons) from - to + ...that's why you put the diodes in backwards! But I've got to admit, your schematic threw me for a loop with those initially shown backwards (against the direction of your arrows). :shock:
Debate? Man, you gotta stop talking to Ben Franklin.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by still_stirrin » Sat Nov 14, 2015 12:42 pm

FuelMaker wrote:...if I put the valves on the outlet side I wont be able to have it failover to passive thermosiphon flow if the pump fails, it'll be too restrictive...hmmm...
hmmm...did you figure out how to design a "perpetual motion machine"??? :roll:

Gravity....it's not just a good idea....it's the law!

And Bernoulli's is relevant here too. And you can't forget about the friction in the piping either. Physics rule!
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by gemcutter » Sat Nov 14, 2015 5:26 pm

how about you just stay thhere and watch the still like you are supposed to and turn it off if the pump fails?

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sat Nov 14, 2015 11:34 pm

gemcutter wrote:how about you just stay thhere and watch the still like you are supposed to and turn it off if the pump fails?
Very easy to say, much harder to do. Especially since I won't have direct line-of-sight to the top of the column, what if I'm reading a book, or taking a crap, or reading a book while taking a crap (had to be said...) since the pump is just about silent my first indication of a problem would be a sudden spew out the product port.

(Well actually it wouldn't, I'd probably get a overtemp alarm first) anyhow I still want to have the ability to have a graceful switchover to convective coolant flow in a long term power-out situation. It adds a layer of safety that doesn't rely on electronics and corrects a problem before it goes "oh shit". And "oh shit" usually rounds down to "boom".
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by raketemensch » Sat Nov 14, 2015 11:50 pm

skow69 wrote:
still_stirrin wrote: You sparky's....a long standing debate about current flow (electrons) from - to + ...that's why you put the diodes in backwards! But I've got to admit, your schematic threw me for a loop with those initially shown backwards (against the direction of your arrows). :shock:
Debate? Man, you gotta stop talking to Ben Franklin.
Ben was known for selling a mighty fine drop.

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by skow69 » Sun Nov 15, 2015 12:36 am

Quite true, but he sure backed the wrong horse on current flow.

Fueldude, are you saying that you expect this coolant to cycle indefinitely all by itself with no pump running at all by means of thermosiphon? (After you reverse the polarity of the diodes, presumably.)


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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FreeMountainHermit » Sun Nov 15, 2015 1:32 am

To me it's overly complicated and has me wondering how big a footprint your rig impacts the area you have available.

30 gallon reservoir or even a 55 with a variable trickle of coolant to the reservoir to maintain a constant temp with separate valving to the RC & PC will get you where you want to be.
Blah, blah, blah,........

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Monkeyman88 » Sun Nov 15, 2015 2:19 am

FuelMaker wrote:
gemcutter wrote:how about you just stay thhere and watch the still like you are supposed to and turn it off if the pump fails?
Very easy to say, much harder to do. Especially since I won't have direct line-of-sight to the top of the column, what if I'm reading a book, or taking a crap, or reading a book while taking a crap (had to be said...) since the pump is just about silent my first indication of a problem would be a sudden spew out the product port.

(Well actually it wouldn't, I'd probably get a overtemp alarm first) anyhow I still want to have the ability to have a graceful switchover to convective coolant flow in a long term power-out situation. It adds a layer of safety that doesn't rely on electronics and corrects a problem before it goes "oh shit". And "oh shit" usually rounds down to "boom".
Need to take a crap? Turn the damn still off. Or shit in a bucket in front of it.

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FreeMountainHermit » Sun Nov 15, 2015 2:56 am

FuelMaker wrote:
Very easy to say, much harder to do. Especially since I won't have direct line-of-sight to the top of the column, what if I'm reading a book, or taking a crap, or reading a book while taking a crap (had to be said...) since the pump is just about silent my first indication of a problem would be a sudden spew out the product port.
Definitely idiot of the month posting material.
Blah, blah, blah,........

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Yummyrum » Sun Nov 15, 2015 3:21 am

FreeMountainHermit wrote:
FuelMaker wrote:
Very easy to say, much harder to do. Especially since I won't have direct line-of-sight to the top of the column, what if I'm reading a book, or taking a crap, or reading a book while taking a crap (had to be said...) since the pump is just about silent my first indication of a problem would be a sudden spew out the product port.
Definitely idiot of the month posting material.
Hmmm Too true blue .......Guess the fuel makers aren't hooch makers...and don't care too much about safety'n things ....like perhaps they should :wave:

Edit:I don't think all makers of ethanol fuel are as careless as this dude....who apparently can't see a puke while shitting and reading a book ...WTF

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FreeMountainHermit » Sun Nov 15, 2015 3:33 am

Shhhhhhhhhh,........ he's an injuneeer.
Blah, blah, blah,........

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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sun Nov 15, 2015 9:36 am

skow69 wrote:Fueldude, are you saying that you expect this coolant to cycle indefinitely all by itself with no pump running at all by means of thermosiphon? (After you reverse the polarity of the diodes, presumably.)
Absolutely, as long as you put heating on one side and cooling on the other side of a closed loop and it'll move the water, and pretty well too. Thermosiphon works because of density differentials the hot side is less dense than the cold side so the hot fluid goes up and the cold fluid goes down. Its why having everything sloped is important.

Its almost universal in solar hot water batch heaters

In a 1 inch pipe you'll get about 500ml/min flow at a 30F degree differential, at the 100+ temp differentials it should rip along pretty good as long as there's no restrictions or excessive friction from roughness at about 3L/min.
Going down a stairstep like I've got it arranged will slow it down a lot. I'm not going to do that now - I'll make my own longitudinally finned tube if I have to.

https://en.wikipedia.org/wiki/Thermosiphon
http://www.erc.uct.ac.za/jesa/volume18/ ... dobson.pdf

And regarding comments from the peanut gallery - thank you so much for your gracious, welcoming, and constructive criticism.

Who probably haven't actually read the thread and don't understand what I'm trying to accomplish enough to comment on it... If you're saying you sit and keep your eyeballs on your still for a 6-8 hour run for every second of that time I doubt your honesty, an "oh shit" only takes less than a minute to happen. Especially if you're pumping 110000BTU into the system with a natural gas burner.

I'm especially irked about the unsafe comment. When the build is complete there'll be numerous safety systems and sensors; overtemp, undertemp, column flooding, low boiler level, gas leak, and even one for carbon monoxide. The problem is they're all electronic, and electronics fail - usually at the worst possible time. Somewhere in there a passive failsafe has to be in place.
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by Monkeyman88 » Sun Nov 15, 2015 11:34 am

FuelMaker wrote:
skow69 wrote:Fueldude, are you saying that you expect this coolant to cycle indefinitely all by itself with no pump running at all by means of thermosiphon? (After you reverse the polarity of the diodes, presumably.)
Absolutely, as long as you put heating on one side and cooling on the other side of a closed loop and it'll move the water, and pretty well too. Thermosiphon works because of density differentials the hot side is less dense than the cold side so the hot fluid goes up and the cold fluid goes down. Its why having everything sloped is important.

Its almost universal in solar hot water batch heaters

In a 1 inch pipe you'll get about 500ml/min flow at a 30F degree differential, at the 100+ temp differentials it should rip along pretty good as long as there's no restrictions or excessive friction from roughness at about 3L/min.
Going down a stairstep like I've got it arranged will slow it down a lot. I'm not going to do that now - I'll make my own longitudinally finned tube if I have to.

https://en.wikipedia.org/wiki/Thermosiphon
http://www.erc.uct.ac.za/jesa/volume18/ ... dobson.pdf

And regarding comments from the peanut gallery - thank you so much for your gracious, welcoming, and constructive criticism.

Who probably haven't actually read the thread and don't understand what I'm trying to accomplish enough to comment on it... If you're saying you sit and keep your eyeballs on your still for a 6-8 hour run for every second of that time I doubt your honesty, an "oh shit" only takes less than a minute to happen. Especially if you're pumping 110000BTU into the system with a natural gas burner.

I'm especially irked about the unsafe comment. When the build is complete there'll be numerous safety systems and sensors; overtemp, undertemp, column flooding, low boiler level, gas leak, and even one for carbon monoxide. The problem is they're all electronic, and electronics fail - usually at the worst possible time. Somewhere in there a passive failsafe has to be in place.
Yes. People do sit in front of their still for 6-8 hours. It's called being responsible. And it is being watched all the time. Gotta swap out the jars before they over flow.

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FuelMaker
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Re: Cooling loop w/ passive pump failover protection (pic)

Post by FuelMaker » Sun Nov 15, 2015 12:15 pm

Monkeyman88 wrote: Yes. People do sit in front of their still for 6-8 hours. It's called being responsible. And it is being watched all the time. Gotta swap out the jars before they over flow.
Riiiiiiiiight, and you never go take a piss or go get a soda while the jar is filling. Well good for you, even when I was in a damn foxhole I never kept my eyes on something continuously for 6-8 hours. Nobody does.

I'm not advocating an unattended still, I'm saying its impossible to watch anything like a hawk without stop for that length of time and "oh shits" can happen extremely fast without something there to catch it.
"A little bit of oops goes a long way."

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