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All about connecting your Cooling Water Supply to your Condensers!

This discussion was created from comments split from: Today in the shed.

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  • edited February 2015

    Some random guy sent me this picture of a souped up Ace of Hearts in his shed.

    Apparently it has a medium condensor for the reflux and a long condensor for the product.

    Random guy said it was on a 30l boiler same as in my shop. If his shed looks like mine it's a coincidence.

    image

    ace1.jpg
    800 x 600 - 67K

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  • edited February 2015

    Looking good @ RandomPunkinGuy.

  • Mixing up the condensers randomdude, nice work.

    Today in the shed I sampled 3 spirits on oak: brandy, bourbon, scotch. Now a couple of weeks ago the bourbon was the winner for me but today the scotch wins hands down.

  • Tell that random guy that his picture is tiny. Can't see shit. It does look like the human hair is connected to the thimble :))

  • @FloridaCracker said: Tell that random guy that his picture is tiny. Can't see shit. It does look like the human hair is connected to the thimble :))

    That's my fault, the original pic got lost during rework for filesize and only the thumbnail remained. Already pinged RandomGuy for re-upload. ;)

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  • Too clean for your shed Punkin... ;)

  • edited February 2015

    The picture is right. Random Guy lives in Lilliput... :))

    I'm more like I am now than I was before.

  • edited February 2015

    @Crozdog, I think George Lucas based American Graffiti on Mainies. That is a happening town!

    (or maybe it was Rebel Without a Cause)

    I'm more like I am now than I was before.

  • Well, RandomGuy has re-uploaded that nice little picture and all OK again. :)

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  • Tell the random guy his reflux condenser will work better if he plumbs the cool water in the bottom.

  • Really? Better than counterflow?

    Would certainly make it easier to bleed the air out, but i always thought counterflow was the preferred method of running a condensor?

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  • edited February 2015

    How hard would it be to put an air release valve at the top of the deflegmator so that you can bleed off all of the air when you run counter-flow?

    Nice setup there @ randomguy !

    I'm more like I am now than I was before.

  • It's really easy, that's how the random guy had his larger crystal dragon set up before. Just a tee at the top with a valve on the branch.
    IHe got that idea from @stubbydrainer who built a condensor in another random build like that.

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  • Do you have a picture or diagram of that? I'm having a hard time imagining the flow path.

    (Too much juniper in the diet does that sometimes. :)) )

    I'm more like I am now than I was before.

  • No, i'll cut a valve in tomorrow and take a pic. The bits should be in the cupboard somewhere. Does @crozdog not show it in the manual?

    Simply the water goes in the top to create counterflow and at the high point of the feed in you have a valve in the top of a tee with a bleed hose.

    Stubby's one has a bleed tapped directly into the top of the condenser which of course is better.

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  • I'm with you on counter-flow heat exchangers. Efficient ones will get the product out temp very close to the cooling water inlet temp. The main drawback is trapped air on the cooling water side when cooling water flows downward. Vent that and counter-flow is the clear winner.

    I'm more like I am now than I was before.

  • edited March 2015

    @punkin said: Really? Better than counterflow? Would certainly make it easier to bleed the air out, but i always thought counterflow was the preferred method of running a condensor?

    Well I learned something about distillation theory today. I run the RC the other way round with the valve on the inlet side. Still not sure that it doesn't give better control of the reflux pool via the temperature of the water in the RC i.e. not trying for maximum reflux all the time, but rather to match the speed of the still to the ABV, which will need adjustment across the run as the boiler charge changes. Sometimes the water in the RC needs to heat up.

    Slower speed of flow seemed to offer more control.

    The eggheads are not sure themselves, see if you can get your head around the following. BTW they think the air will exit the condenser either way.

    The key words here are "In Theory at least".

    In practice in 99.9 % of cases it will not matter for following reasons:

    1. Normally the water flow rate is very high compaired to the flow of condensing vapours. This is confirmed by very little increase in outlet temperature of water.
    2. Condensation of vapours is an isothermal process. So strictly for condensation there is no co-current or counter-current flow. It is the sub-cooling of the condensate for which the flow regime becomes relevent, and in case of vertical reflux condenser, with water inlet at the bottom, it becomes counter-current flow.

    The measure of true counter-current flow is a factor called LMTD - Log Mean Temperature Difference. (A cursory reading of any Chem Engg text on Heat Transfer will explain it) If the temp change in cooling water is not significant by reversing the flow, then the LMTD hardly changes which means there is no great advantage in the counterflow arrangement.

    Gsd

    Reference: Counter current exchange for reflux apparatus @ Sciencemadness Discussion Board

    Guess I need to think on it some more.

  • edited March 2015

    If I am being honest, I should also admit that I think the best way to run the condensers is with completely separate lines because the flow rates are so radically different and I don't measure the temperature into the RC, I do it by feel, and use clear water lines so I can see at a glance how much water is present.

  • edited March 2015

    They lost me at point # 1 above:

    This is confirmed by very little increase in outlet temperature of water.

    Controlling outlet water temp from the dephlegmator is what controls reflux (hence the term "cooling management") which controls the nature of the product.

    On my plated column I always run separate cooling water to the dephlegmator and the product condenser (running parallel). My cooling water is once-through rainwater catchment, so the cooling water inlet temp does not change across the entire run.

    On my packed VM column I run the two condensers in series, counter-flow. It is vapor management, so as long as the condensers knock down all of the vapors, cooling water temp is not important. But I do use the temperature change and flow rate to estimate the heat input (in Watts) on my propane-fired boiler.

    I'm more like I am now than I was before.

  • There is a point worth stressing here. Heat exchangers work best when running counterflow, because you are trying to transfer as much energy from 1 side of the exchanger to the other.

    A dephlegmator is very different. You only want to transfer enough energy to condense the vapour. Subsequent cooling of condensate is UNDESIREABLE. Your exit coolant should be hot, probably with a slow flow rate.

    On a product condenser you may wish to actually cool the condensate a bit, meaning faster coolant flow rates.

    Don't confuse heat exchangers and dephlegmators. They are slightly different applications of the same bit of thermodynamics theory.

  • Cool, i'll swap it round. On my bilge pump running with the inlet at the bottom on the big rig there was not enough cooling to get 100% reflux at a decent rate, so i swapped it round to counterflow and it managed.

    I have since upgraded and added a larger pump, so even on this small one it's gunna be enough.

    There is two separate inputs coming from a Y in the pump line going to each condensor with the reflux condensor controlled with a valve on the exit. The two hot lines join back together and go back to the tank.

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  • A deflegmator is heat exchanger that is operated with a controlled efficiency to set the desired reflux rate.

    I'm more like I am now than I was before.

  • …with the addition of vapor enrichment/mass transfer as condensate and vapor move countercurrent through the tubes.

  • edited March 2015

    @punkin said: There is two separate inputs coming from a Y in the pump line going to each condensor with the reflux condensor controlled with a valve on the exit. The two hot lines join back together and go back to the tank.

    I have a Y on the pump and each port in the Y piece has a ball valve, so the gross flow to the two condensers lines can be controlled independently, the restriction on the RC side forces extra to the PC side.

    My premise has been that control of the RC is the key to H/T compression and runs that vary only a couple of % ABV across the run. Really interested in other ideas.

    @grim said: …with the addition of vapor enrichment/mass transfer as condensate and vapor move countercurrent through the tubes.

    BTW I don't believe this, I just don't see it as important. Logic says flow should be laminar in both water and vapor, especially if the setup is not counter-current. Differential heat transfer between the inlet and outlet could cause disruptions. However they can see inside their condensers so I'll have to defer...

  • edited March 2015

    Here's an interesting cooling idea, may not work but nothing ventured, nothing gained, this will hopefully solve the problem of adjustments to the Deflag flow affecting the flow in the Product condensor when both feed from a Y connector from the same source.

    So here goes First you fit a T piece at the inlet and outlet of the RC and join the two T's together with a flow control valve in the middle, it's effectively a bypass in parallel with the deflagemator, you still have your other two valves for control as normal and you start with the new bypass valve closed.

    Once your rig is up and running and you have 100% reflux, you can adjust the reflux percentage by opening the new bypass valve, this will divert water flow through the new bypass, reducing the flow in the dephlagmator and controlling the reflux.

    With this method the overall flow rate trough the RC branch always remains constant and adjustments don't affect the flow to the product condensor.

    I don't have my new still yet but I'll be trying it out when it arrives from @SDEurope.

    I think it'll work, but you guys have the experience, I'm just an engineer with an idea!

  • Interesting idea Anavrin this is assuming that both condensers are rigged in series? Great idea. Do you think there would be an advantage when the condensers are on separate lines?

  • I don't think you'll get fine enough control. The RC really gets to a trickle when collecting hearts.

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  • It should work in series, but you still get the same problem when both are connected in parallel from a single source using a Y connector, which is how I think most people have it set up.

    Even in parallel on a Y connector, if you restrict one branch it increases the pressure in the other branch, if the resistance of the second branch is not too high, then the flow in the second branch will increase and vice versa.

    My only concern with this is will one bypass valve offer enough control, maybe more than one valve, or a bigger diameter bypass pipe might be needed, especially on a big still with a bigger dephlagmator.

  • VM and I run the cooling in series PC first and RC second...I use the exiting qater temp to make sure I'm not wasting water. If the water exiting the RC stays under 140F I'm assured of no vapor venting. And if is much below 140F I'm wasting water.

    DAD... not yours.. ah, hell... I don't know...

  • @punkin said: I don't think you'll get fine enough control. The RC really gets to a trickle when collecting hearts.

    That's what I was worried about when I said one valve might not be enough or a bigger diameter might be needed, in theory if the bypass could be opened enough most of the flow would go through it and only a trickle would be left flowing in the RC, some experiments are required I think.

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