Condenser capacity in BTU's

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Condenser capacity in BTU's

Postby Twisted Brick » Wed Oct 04, 2017 2:00 pm

First off, since this is my first non-intro post, thanks gentlemen and ladies for the goldmine of knowledge and experience you all so generously provide.

I stripped my first generation of UJSSM yesterday, and all went well. My still is a 3” pot/head with 7” riser (without the 3” Tee in the pic) off a 1/2 keg running into a 2” x 21” (4 x 1/2) shotgun. I was able to collect 4l in the first hour. Starting at 60 ABV, I collected down to 20 ABV and got a total of 6.3l in 1hr 40min from a 7gal charge.

First question: I’m recirculating 170 gph in a 30gal plastic drum, which raised the coolant temp from 73F to 118F in 1hr 40min. After 40min the shotgun shell was noticeably hot. This did not happen during my shorter cleaning and sac runs. Is there an optimum way to run the shotgun/water flow? Ambient temp was 75F.

Second question: I’m currently looking at NG burner models with output from 80k to 120k btu’s. For those running NG, what are you running and are you happy with your current output? Also, are more btu’s generally required the larger diameter a still is?

I would like to find out how hard this condenser can be pushed and wonder what it will take in power. It is 21” long and has 7 baffles inside.

Thanks.
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Re: Condenser capacity in BTU's

Postby Kareltje » Wed Oct 04, 2017 2:58 pm

British Thermal Units? Are they still used?
1 Btu = 1.055 kJ
I do not calculate my condenser capacity. I adjust my energy or my waterflow according to the cooling of the product.
In other words: I run and calculate afterwards.

Very nice looking still, by the way! :thumbup:
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Re: Condenser capacity in BTU's

Postby The Baker » Wed Oct 04, 2017 3:48 pm

Hi,
I am running my pot still on natural gas in a small way.
Twenty litre stock pot with a somewhat undersized liebig condenser; it used to be a somewhat oversized condenser on a six litre pot but that was too slow, having to change over too often. I just don't run it too fast on the spirit runs.
(I might use the six litre one for gin).
Source of heat is the wok burner on the side of my grill and it works fine.
Stock pot cost $65 Australian dollars, condenser cost a bit for fittings but I had the copper tube and a friend made it up.
Natural gas is great, a lot cheaper than propane bottles and you never run out, never have to buy another bottle.

Geoff
P. S. The condenser is inch and a half O.D. and seventeen inches long (the outer tube). The inner (vapour) tube is half inch O.D., (probably a bit small but it was 'designed' for the little boiler.... ) no baffles. I could have used smaller tube for the outside tube and that may have been better; I used what I had.
Though in hindsight I may have saved enough on smaller fittings to buy a short length of narrower tube for the outside.... G.
Last edited by The Baker on Wed Oct 04, 2017 4:01 pm, edited 2 times in total.
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Re: Condenser capacity in BTU's

Postby still_stirrin » Wed Oct 04, 2017 3:57 pm

Twisted Brick wrote:First question: I’m recirculating 170 gph in a 30gal plastic drum, which raised the coolant temp from 73F to 118F in 1hr 40min. After 40min the shotgun shell was noticeably hot. This did not happen during my shorter cleaning and sac runs. Is there an optimum way to run the shotgun/water flow? Ambient temp was 75F.
That’s about right. I like the shotgun’s coolant output temperature to be around 120*F, which is about where you are.

Incidently, that shotgun will have plenty of power capacity. Well built with a good design. It’ll manage well with your 3” riser and the power you can push through it.

Of note, when the reservoir heats up quickly, it means you’re extracting as much of the heat input into the boiler as possible, ie - great condenser heat capacity. Efficiency relates to the flowrate of the coolant needed to extract that much heat. So, I would expect the riser temperature to increase proportional to the burner settings...higher fire...faster reservoir heat up.

Twisted Brick wrote:Second question: I’m currently looking at NG burner models with output from 80k to 120k btu’s. For those running NG, what are you running and are you happy with your current output? Also, are more btu’s generally required the larger diameter a still is?
BTU’s are a measure of energy...kJoules as Kareltje pointed out. Typically, we measure energy per unit time, ie - BTU’s per hour which can be converted to kWatts: 1 kW = 3412 BTU/hr

So, a 120 kBTU/hr burner is 120,000/3412 = 35.2 kW and an 80 kBTU/hr burner is 80,000/3412 = 23.4 kW. Both of these are FAR more power than you’ll need for distillation. Most likely, you’ll need to throttle them waaaaaaaay back when producing.

I would say that for the most part, your 3” riser will use in the neighborhood of 2kW to 4kW for your product runs. You can get away with a little more power when doing a stripping run, but 80 kBTU/hr is overkill. But....I also suspect that the “rated energy/hr” is over-rated too. You simply won’t get that much heat out of it. It does make good marketing for them, however.

Twisted Brick wrote:I would like to find out how hard this condenser can be pushed and wonder what it will take in power. It is 21” long and has 7 baffles inside.
You’ll be able to put a lot of power to it...I’d expect well above 5.5kW. But, that’s still below the “marketed power” of your burner. In practice, I think you’ll get plenty of knockdown power out of that shotgun. The weak point of your system will be your reservoir. At max power through the duration of a run, you’ll need a big tank...maybe even a hottub to manage the heat transfer.
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Re: Condenser capacity in BTU's

Postby NcHooch » Thu Oct 05, 2017 5:35 am

still_stirrin wrote:You’ll be able to put a lot of power to it...I’d expect well above 5.5kW. But, that’s still below the “marketed power” of your burner. In practice, I think you’ll get plenty of knockdown power out of that shotgun. The weak point of your system will be your reservoir. At max power through the duration of a run, you’ll need a big tank...maybe even a hottub to manage the heat transfer.
ss


Agreed. my cooling reservoir is a 55 gallon "Brute" trash can. and even that gets warm during a long run.
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Re: Condenser capacity in BTU's

Postby HDNB » Thu Oct 05, 2017 6:15 am

so in my experience a 21 inch shotty will cool about 4600 watts on a recirc system. if you throttle the output water side of the shotty it will take longer to heat the reservoir to the "too hot" point.

practically speaking you would strip at 3000 watts and spirit run at 2000 watts on a 3" column (ballpark-ish)

at 30 gallons you will prolly change out 10 gallons of water twice to keep things cool on a boiler of 50-ish litres. (assuming pot mode)

an 80000 btu heater is overkill in the extreme. as noted up there, thats 23400 watts, enough heat to bring 300+ litre to a boil in an hour...assuming 70watts/litre/hour, so you will obviously have a much smaller than maximum flame working out of the unit.

not that i'd suggest it... but at full smoke, 80k btu would flash boil a 50L kettle in about 9 minutes...causing all sorts of potential safety and product quality issues.
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Re: Condenser capacity in BTU's

Postby Twisted Brick » Thu Oct 05, 2017 8:51 am

Thank you for your replies, gentlemen.

still_stirrin wrote:The weak point of your system will be your reservoir.


Duly noted. Luckily, I recently picked up a 55 gallon plastic drum and dolly, but would also like to try cooling the exit water prior to re-entry into the reservoir. Maybe something like a baseboard heat exchanger and fan? 'Course, there's always the suspended towel cooler.

still_stirrin wrote:That’s about right. I like the shotgun’s coolant output temperature to be around 120*F, which is about where you are.

and

Efficiency relates to the flowrate of the coolant needed to extract that much heat


That's valuable info right there.

HDNB wrote:so in my experience a 21 inch shotty will cool about 4600 watts on a recirc system. if you throttle the output water side of the shotty it will take longer to heat the reservoir to the "too hot" point.


So... 4600 watts = 15,600 btu's. That's why it got so hot! My burner is a Camp Chef ("advertised" 30k btu) stove that I ran full bore but at least with no vapor. This is why I ASSumed I could go higher on the btu's so I could decrease the time needed on my strips. Gonna have to go the other way and find what impact a lower flame has on stripping collection rate. For sure I'm gonna try throttling back the water input rate.

Thanks again, guys. I thought most guys were running higher btu's since internal elements seem to be more efficient heaters.
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Re: Condenser capacity in BTU's

Postby HDNB » Thu Oct 05, 2017 7:00 pm

My burner is a Camp Chef ("advertised" 30k btu) stove that I ran full bore but at least with no vapor.


at that much heat, i'm surprised you didn't have a jet of vapour 15 feet out the spout! mine blows steam at 17 amps/240vac (4100w) but it does not have baffles...i'd assume those help a bit

you must have had an incredible take off rate...9LPH? 10? more?
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Re: Condenser capacity in BTU's

Postby Twisted Brick » Fri Oct 06, 2017 12:05 pm

Twisted Brick wrote:you must have had an incredible take off rate...9LPH? 10? more?


Hardly! My take off rate is 4LPH. Based on accounts from others' output rates, I thought for sure a 3" pot and shotgun would be a little more than that. That's why I'm baffled to hear that 30k btu's is on the extreme side. What could be holding the output rate back? Vapor speed?
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Re: Condenser capacity in BTU's

Postby HDNB » Fri Oct 06, 2017 5:39 pm

well that does not make sense.

i'm talking 2" column on a 2" x 21" copper shotty with 4 x 1/2 vapour tubes on my end...at 17 amps before she steams i'm pouring out at maybe 6-7 LPH.

at 4lph i'm at 12amps
at 3lph it's running 7amps

this is just my experience, i'm not using math.


maybe PM LWTCS and ask or direct him here, i'm pretty sure he has through- put calcs for column size, min/max powers and knock down rates for different condensers.
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Re: Condenser capacity in BTU's

Postby Twisted Brick » Sat Oct 07, 2017 8:28 am

Thanks HDNB,

Something doesn't add up. I'll contact LWTCS for his column calcs, but only after a run with the column insulated first. (The boiler was insulated).

Nice that you get 6-7 LPH...
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Re: Condenser capacity in BTU's

Postby HDNB » Sat Oct 07, 2017 8:49 am

actually i don't. usually run at just under 3LPH to hit the sweet spot. (6.6 amps)
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Re: Condenser capacity in BTU's

Postby Twisted Brick » Sun Oct 08, 2017 9:07 am

Ok... so I stripped another batch of UJ yesterday, ditching the riser and attaching the pot head directly to the 2x3" reducer coming off the keg. I draped a towel on top of the head, so there was no part of the riser or insulated keg exposed to what turned out to be a tiny breeze throughout the run on this 90F day.

LPH increased to 4.5.

Something else I discovered: the bottom of my keg came slightly pushed in, and along with the skirt, raises the distance so the flame doesn't touch the bottom. I need to research what others are maintaining for flame contact, especially Camp Chef users.

BTW - On a strip run, what is "the sweet spot"?
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Re: Condenser capacity in BTU's

Postby HDNB » Sun Oct 08, 2017 9:20 am

on my 2" it strips nice at 12amps. maybe 4ish LPH. I've gone hotter, doesn't really affect the booze other than pushing more water into the low wines. I don't like going higher though because ya turn your back on it for a second and shit can go sideways fast.

at 12 amps, shit just goes sideways quickly, but within the reaction time of my particular vintage. :D

i'd think a 3" would produce 50% more given the same wash and heat. (guessing?)

i don't think you actually want flame contact, but maybe a propane user would give some experience there. (i use electric/direct and natural gas on an efficient boiler)
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Re: Condenser capacity in BTU's

Postby NZChris » Sun Oct 08, 2017 12:33 pm

You can make a coolant reservoir last a lot longer by not mixing the hot back in with the cold. Draw from the bottom of the reservoir keeping the flow to a minimum to maximize the temperature of the return water and return it to the top of the reservoir creating as little turbulence as possible. To maximize the efficiency, you can use a valve or pump and a cheap controller to automate control of the condensate output temperature to the maximum you are comfortable with.

If you do have to add cold during a run, add at the bottom and overflow the hot water from the top.
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Re: Condenser capacity in BTU's

Postby Twisted Brick » Mon Oct 09, 2017 10:49 am

Thanks Chris,

My condenser isn't showing signs of reaching capacity (visible vapor) but it sure heats 30 gallons up really quickly. Guess I'll learn to live with it (on strips).
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Re: Condenser capacity in BTU's

Postby Kareltje » Mon Oct 09, 2017 2:00 pm

Another way of cooling is by vapourizing water.
I saw some thread of a device to cool cooling water by letting it drip through sheets hanging in the air. (So it seemed, anyway!) You could make the returning hot water from the condenser loose a lot of heat by vapourizing.
I sometimes use some damp rags on my spiral riser or spiral cooler and this works very fine. The visible vapour coming from it find its counterpart in alcoholic vapours condensing in the pipes.

It of course makes your working place a bit wetter, but when you have ample ventilation (as you always should!) that should be no problem.
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Re: Condenser capacity in BTU's

Postby The Baker » Tue Oct 10, 2017 7:32 am

My condenser is a little under-powered so I will try a damp cloth on the copper tube that sticks out at either end of it. Should be just enough to make a bit of difference.

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Re: Condenser capacity in BTU's

Postby Twisted Brick » Tue Oct 10, 2017 10:15 am

I've often wondered how effective a condenser with external copper fins and a fan would be at reducing the coolant temperature.
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Re: Condenser capacity in BTU's

Postby RedwoodHillBilly » Wed Oct 11, 2017 7:34 am

Twisted Brick wrote:I've often wondered how effective a condenser with external copper fins and a fan would be at reducing the coolant temperature.


Very. I have 2 transmission coolers with fans in series. Works very well, they keep the coolant temperature down and also heat my basement when running.
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Re: Condenser capacity in BTU's

Postby Twisted Brick » Thu Oct 12, 2017 3:33 pm

That's excellent, what with the bonus of having a radiating room heater.
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