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Super Dephlegmator Build Issues



  • More equal temperature dissipation while cooling medium flows through it. So it should better cool down. It's not tried yet. As it will be tried, the answer will pop put. Please give me some time to run it :)

  • Cool idea on the baffled defleg. I have always wondered what keeps the water from just going straight in and then straight up to the exit on the SD defleg without capturing the cooling from around all of the tubes?

  • Almost makes me want to change either the inlet or outlet to an opposite side. Especially when the flow is very low I would think that the opposite side would be a lot cooler with very little flow. Smaug? Punkin? What say you guys?

  • Thats why we developed the super condensors. The copper condensors we are offering can have baffles. The same side is a little better than opposites. there's a neat diagram rouind somewhere that @Harry postd that shows the flows in all the condensors.

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  • edited July 2015

    So what happens when you don't model your baffle geometry and get the fluid dynamics correctly? Suspect you might end up with a heat exchanger that actually performs worse than one that doesn't have baffles. But that math is beyond my pay grade so who knows?



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  • @punkin said: The copper condensors we are offering can have baffles.

    They're available? Got a link?

    There are add ons for Inventor that does fluid sim but a good eye will get you most of the way.
    Just make the cross sectional flow path as even as possible. Make it large for high flow rate and small low ones. It would be difficult to make it worse than without any baffles at all, it would just be less than optimum.

  • I don't have them in stock but can get pricing for those with the dollars to spend.

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  • edited July 2015

    I'm pro-baffle, but just playing devil's advocate here. I like to do that whenever I see something that seems to be accepted as status quo.

    But just so I understand this correctly, the specific benefit would be better heat transfer, but the actual hands-on, real-world benefit would be...

    Less water usage due to lower flow rates needed?


    Ability to run with a higher input temperature?


    Ability to use a smaller heat exchanger?

    The first point is interesting for those who use municipal water, since it means using less water, but would probably not be interesting for those who recirculate.

    The second point is interesting for the folks down south, and probably the folks who recirculate. For the southerners, it means less water used, for the recirc, it means being able to run longer as reservoir temps go up.

    I guess the third point is interesting for folks with height challenges, but traditionally reflux condensers aren't very tall. And I think realistically, we would only be talking about a couple of percent shorter condensers.

    The trade off here is that I think you'll hit a point at which a larger, cheaper heat exchanger will perform equivalent to a smaller, more expensive one. From a ROI perspective, making the dephlegs taller, with more ports, was, I think, the absolute right approach. I think this is more of a balancing act than better vs worse or right vs wrong.

    Personally, I think the big benefit to optimizing is for those who can't recirc, and use city water, where city water is non-optimal, either too hot, or too expensive. Second best would probably be for those who recirc, and are in geographies where they may be able to get away with not having to actively cool their reservoir, meaning big $$ savings in electric. Or those who simply want the bling. :)

  • I fall into the second category and if I could optimize the defleg it would mean that my reservoir would not increase in temp as quick, like you pointed out. When the water in the tank starts at 90F, the longer I can keep it under 95 the better.

  • edited July 2015

    @FloridaCracker - The thermodynamics police are going to give you a ticket. Your reservoir is going to increase at the same speed, regardless of the heat exchanger. Every BTU removed from the condenser is added to the reservoir (oversimplification). All we're talking about is getting that BTU from the condenser to the reservoir more efficiently (in our case, that means with less flow).

    The benefit for you, I think, is that instead of hitting a wall at 95f, you hit the wall at 97f. The higher heat transfer coefficient provided by the baffles means you'll be able to pull off the same amount of heat, with the same flow rate, with a slightly higher input temperature.

  • Kinda.

    I agree with most of your points grim but there is another for my current situation.

    With very low, laminar flow and no baffles the outlet will actually have a range of water temps coming through an any one time. With the system I'm building this could potentially cause big errors in my temp measurements. The quick fix is to add three baffles.

    With FC's comment he's kinda right too. If you can get you outlet temp higher while getting the same RR, the column shouldn't really know the difference but the line returning the your tank will be a lot hotter. The difference in temp between the air and the line will be greater so it will cool quicker (and of cause the water usage will drop right down too). Same power, just lower flow and higher temp. The higher deltaT means more efficient heat transfer getting the heat back out of your water.

  • I really shouldn't fret too much over this because I recently added a large auto radiator to my return lines. Makes a huge difference in the temp of my reservoir increase over a run. Instead of scalding hot water going back in, it is like bath water warm. And Grim I see your point; either a little bit of scalding water or an increase in volume of very warm water. Same overall heat added to the tank. Still wonder about the inlet located just below the outlet on the defleg. Doesn't seem like it would get much crossflow across the tubes.

  • Point is, even with your radiator, its a lot easy to get the heat out of a small amount of very hot water compared to a lot of just warm water. Evan tho there may be the same amount of energy in both.

  • edited July 2015

    There are all sorts of games you can play to increase delta t and the output temp. For example, add a pump inside the control loop so that you have recirculation across the heat exchanger, and can push very high flow rates across the heat exchanger at higher coolant temps. Or, just use a larger heat exchanger than you need and run a slower coolant flow. Or add baffles and do all three.

  • Man, my spelling and typing is terrible. Apologies.

  • edited July 2015

    I deleted my last point on that last comment because I think I'm wrong, but not 100% sure. My premise was:

    When product temp = input coolant temp and vapor temp = output coolant temp, you've essentially hit the limit of performance and will not gain much from increasing your heat exchanger performance. But the wildcard here is always going to be flow rate and size. There is going to be another limit on the minimum flow rate based on the heat carrying capacity of the coolant as well.

  • Not sure what your trying to say,

    "When product temp = input coolant temp and vapor temp = output coolant temp"

    Pout=Cin & Pin = Cout Isn't that 100% efficiency? How are you going to improve on that?

    Is your point that 100% efficiency for one duty won't apply for a different duties i.e. If you change flow rates?

  • edited July 2015

    Ah, the point I was getting at is that you could look at your actual numbers and determine whether or not there would be any real-world benefit. If output temp was within say, 5 degrees of vapor temp, and you were flowing 1gpm, realistically how much additional real world benefit would you see from trying to improve your heat exchanger so you were within 2 degrees of vapor temp. You'd gain what, maybe a 2-5% reduction in flow rate? (cue hypothetical oversimplification)

    Lets say you need to remove 50k BTU to condense, running 1 gallon a minute, 70f input, 170f output, 175 vapor temp. You can not increase your output temperature any further without causing vapor to pass.

    Now you improved your hx performance and can push the output to 173f without passing vapor.

    To remove that same 50k BTU (you can't change that number), you'll run .965 gallons a minute, 70f input, 173f output, 175 vapor temp.

    You've spent all that time, effort, and money, to gain a 3.5% reduction in flow rate. Was that worth the investment?

    Now, if you were running a hx that required 2gpm, 70f in, 120f out for the exact same scenario, maybe there would be a benefit in improving, as you would save around 300 gallons of water over a 5 hour run. Or the higher delta t output lets you run a radiator to more efficiently cool your coolant before it goes back to the reservoir.

    But baffles aren't going to compensate for insufficient size. The elephant in the example is the 50k BTU heat load, that number you can not change. It dwarfs everything else.

  • Law of diminishing returns, sure.
    A more efficient heat exchanger is more expensive but so is more energy.
    Lower flow and higher inlet temps mean our pumping requirements can go down and so can the cooling requirements.

    How much of a commercial distillery's budget is literally burned on energy use?
    Take out heating, cooling, and pumping and there isn't much left.
    Would you rather save a couple hundred bucks on a less efficient design or pocket 1% of the plants yearly energy costs in savings.
    Not such a big deal in a garage but on a bigger scale a bit of foresight can save a hell of a lot of money.

  • edited July 2015

    Yeah I agree, more than 1 way to skin a cat. We haven't even touched on turbulators for the vapor side. If we are talking super, we need to reopen the discussion about running the dephlemator countercurrent, both two other good options to improve performance.

    I've been meaning to buy some .050-.010" copper foil and cut some turbulators.

  • Dephlemator counter current is a whole other can of worms.
    Counter current to the vapour or condensate?

    With the phase change, counter current to the vapour is a bit meaningless but the myth still persists.
    Think about what's actually going on... There's no deltaT in the vapour so how is counter current going to make any difference?
    If you get why counter current is normally important it should be obvious that isn't relevant here.

  • Sorry guys, left my degree in thermodynamics laying right next to my degree in astrophysics. On the subway I believe. Anyway, since I upgraded to the 275 gallon tote for a reservoir I had a lot more to play with. THEN I added the 5" defleg. After that I added the radiator. I've seen very noticeable positive improvements after each but think that I have hit the wall. JB's diminishing returns. Now that it is over 90F here each day, the tank rarely goes below that number but I have learned how to overcome it. Where there's a will......

  • It's usually pretty easy to move a wall in engineering

  • @jacksonbrown said: It's usually pretty easy to move a wall in engineering


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  • I think florida needs to dig two pits, one for the dunder and one for his tank.

  • Or, dig a trench and bury a hose or pipe in it and recirculate through after the radiator

  • Oh the dunder LIKES it hot. It is sitting in the garage just minding it's own business. It will come forth again in a day or two when I summon it for my next rum wash.

  • edited July 2015

    Would anything like this work to help with turbulence?


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