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Shotgun Baffle Design

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  • Zapata Vive
    (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here) I m building a shotgun. 2 shell about 17 long
    Message 1 of 10 , Oct 9, 2013
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      (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

      I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

      I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
      Image
      Of course it will be our standard single pass design instead of the double pass pictured there.

      Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

      Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

      I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

      If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
      Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
      I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

      I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

      Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
      shotgun endplate template 1 offset v8 (400x194).jpg
      shotgun endplate template

      Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
      I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

      I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...
    • daryl_bee
      Baffles? I m just coming up the home stretch on a shotgun/firebox condenser (core approx 3 x 12 ) and now you have me wondering if it will work - I have no
      Message 2 of 10 , Oct 11, 2013
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        Baffles? I'm just coming up the home stretch on a shotgun/firebox condenser (core approx 3" x 12") and now you have me wondering if it will work - I have no baffles. Pics below;


        http://surfin_dude.tripod.com/Condenser_02_Assembling.jpg

        http://surfin_dude.tripod.com/Condenser_03_The_Core.jpg

        http://surfin_dude.tripod.com/Condenser_04_Together_Unfinished.jpg


        It's going to be for a ~4KW pot still. It has thirty one 3/8" tubes through it inside the 3" body. Water is simply to go in at the bottom (side hose fitting) and out at the top. I can hold water inlet temp to 15C. There's about 2.35 sq in open area for the vapour to flow through.


        It took nuclear amounts of heat to solder it but I've since pressure tested it to about 60psi and it's good. Do you think channeling will be an issue?


         



        ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

        (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

        I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

        I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
        Image
        Of course it will be our standard single pass design instead of the double pass pictured there.

        Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

        Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

        I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

        If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
        Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
        I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

        I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

        Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
        shotgun endplate template 1 offset v8 (400x194).jpg
        shotgun endplate template

        Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
        I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

        I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...
      • Zapata Vive
        baffles are NOT necessary, in fact it seems very few use them. I m putting them in just because I know they can t hurt and I don t know exactly how much
        Message 3 of 10 , Oct 11, 2013
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          baffles are NOT necessary, in fact it seems very few use them.  I'm putting them in just because I know they can't hurt and I don't know exactly how much they'll help to decide if the (minimal) effort and material is worth the unknown performance gain.  I'm assuming baffles are helpful, or they wouldn't be in professional designs.  How well they work, what exactly they affect, and what their design parameters are seems to not have been studied in our hobby so far as I'm finding.

          Going off what have people proven to work, they aren't needed.  A completely made up number here, but from the builds I've looked at, I'd say 90% or more don't use baffles.  If you read someone just say they use a shotgun, I'd say they probably didn't build it with baffles.

          I wouldn't worry, 31 x 3/8" x 12" tubes seems like plenty to knock down 4 kw, it's comparable to a 31' liebig!


          On Fri, Oct 11, 2013 at 4:19 PM, <darylbender@...> wrote:
           

          Baffles? I'm just coming up the home stretch on a shotgun/firebox condenser (core approx 3" x 12") and now you have me wondering if it will work - I have no baffles. Pics below;


          http://surfin_dude.tripod.com/Condenser_02_Assembling.jpg

          http://surfin_dude.tripod.com/Condenser_03_The_Core.jpg

          http://surfin_dude.tripod.com/Condenser_04_Together_Unfinished.jpg


          It's going to be for a ~4KW pot still. It has thirty one 3/8" tubes through it inside the 3" body. Water is simply to go in at the bottom (side hose fitting) and out at the top. I can hold water inlet temp to 15C. There's about 2.35 sq in open area for the vapour to flow through.


          It took nuclear amounts of heat to solder it but I've since pressure tested it to about 60psi and it's good. Do you think channeling will be an issue?


           



          ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

          (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

          I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

          I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
          Image
          Of course it will be our standard single pass design instead of the double pass pictured there.

          Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

          Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

          I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

          If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
          Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
          I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

          I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

          Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
          shotgun endplate template 1 offset v8 (400x194).jpg
          shotgun endplate template

          Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
          I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

          I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...


        • Eddie Hoskin
          Working around really big heat exchangers, many don t have baffles.  They create more restriction in the flow path and opportunities for vibration wear, which
          Message 4 of 10 , Oct 12, 2013
          • 0 Attachment

            Working around really big heat exchangers, many don't have baffles. They create more restriction in the flow path and opportunities for vibration wear, which needs to be balanced against the additional gain in efficiency you may get. Nearly all are of the industrial design you initially linked to.

            IMO, baffles are totally overkill for a distiller. Worse comes to words you could simply add a couple inches to the length and you'd get the same efficiency.

            Most important with tube and shell hx's is to ensure a food 'fill' on the shell side. That is to say, ensure there are no air bubbles, much like bleeding a radiator. To that end,if you are going to have the inlet for cooling water on the top, and the outlet on the bottom, I recommend you put your flow control valve on the outlet. When starting the still run, close the outlet valve and fill the shell with water. When full, hook up your water source (with full hoses), turn on the water source, and only then crack open the outlet valve to control cooling flow.

            Hope that helps,
            RadicalEd

            Sent from Yahoo Mail on Android



            From: Zapata Vive <zapatavive@...>;
            To: <Distillers@yahoogroups.com>;
            Subject: Re: [Distillers] RE: Shotgun Baffle Design
            Sent: Fri, Oct 11, 2013 11:19:30 PM

             

            baffles are NOT necessary, in fact it seems very few use them.  I'm putting them in just because I know they can't hurt and I don't know exactly how much they'll help to decide if the (minimal) effort and material is worth the unknown performance gain.  I'm assuming baffles are helpful, or they wouldn't be in professional designs.  How well they work, what exactly they affect, and what their design parameters are seems to not have been studied in our hobby so far as I'm finding.

            Going off what have people proven to work, they aren't needed.  A completely made up number here, but from the builds I've looked at, I'd say 90% or more don't use baffles.  If you read someone just say they use a shotgun, I'd say they probably didn't build it with baffles.

            I wouldn't worry, 31 x 3/8" x 12" tubes seems like plenty to knock down 4 kw, it's comparable to a 31' liebig!


            On Fri, Oct 11, 2013 at 4:19 PM, <darylbender@...> wrote:
             

            Baffles? I'm just coming up the home stretch on a shotgun/firebox condenser (core approx 3" x 12") and now you have me wondering if it will work - I have no baffles. Pics below;


            http://surfin_dude.tripod.com/Condenser_02_Assembling.jpg

            http://surfin_dude.tripod.com/Condenser_03_The_Core.jpg

            http://surfin_dude.tripod.com/Condenser_04_Together_Unfinished.jpg


            It's going to be for a ~4KW pot still. It has thirty one 3/8" tubes through it inside the 3" body. Water is simply to go in at the bottom (side hose fitting) and out at the top. I can hold water inlet temp to 15C. There's about 2.35 sq in open area for the vapour to flow through.


            It took nuclear amounts of heat to solder it but I've since pressure tested it to about 60psi and it's good. Do you think channeling will be an issue?


             



            ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

            (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

            I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

            I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
            Image
            Of course it will be our standard single pass design instead of the double pass pictured there.

            Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

            Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

            I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

            If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
            Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
            I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

            I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

            Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
            shotgun endplate template 1 offset v8 (400x194).jpg
            shotgun endplate template

            Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
            I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

            I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...


          • Zapata Vive
            Harry has been telling us this for years, but it really is all in the library. So I dove in, took up The Heat Exchanger Design Handbook and did a lot of
            Message 5 of 10 , Oct 17, 2013
            • 0 Attachment
              Harry has been telling us this for years, but it really is all in the library.  So I dove in, took up The Heat Exchanger Design Handbook and did a lot of unnecessary calculations on baffle spacing for support and vibration reduction, all leading up to baffle spacing being pretty irrelevant on our small designs.

              But then amongst many other criteria, I did find that baffle spacing should be no more than shell diameter, and no less than 50mm regardless of other parameters.  So basically for a 2" nominal shell, 50-50.4mm spacing is best for flow considerations.  I posted a bit more in my thread on MD if anyone wants the specifics.

              And I'm not discounting what you're saying at all Ed, I just got curious why I've never seen anyone actually calculate the design or effect of baffles.  I don't really think vibration will be much of a concern for us, but I could be wrong.  Of the shotgun builds I've seen using baffles, none complained of vibration or noise, even one that used beer cans for the baffles!  So far as flow goes, I'll calculate it too if I can, test it if I can't, but I just don't see a few baffles 2" apart restricting flow even as much as the supply hose does.

              The air purging is a very good point though, and I think it's important for a lot of condensers.  angled liebigs purge readily, but my crossflow condenser for example doesn't always purge fully if I start flow while it's up in the air, so I've taken to starting the pump before I mount it, while I can put it at various angles with the ports facing up.

              Whether or not baffles are necessary, I'll actually calculate their effect.  I just got my hands on a fancy condenser calculator program, and should be able to run a standard design through with and without baffles if I can figure out all the other inputs properly....


              On Sat, Oct 12, 2013 at 7:26 AM, Eddie Hoskin <eddie_hoskin@...> wrote:
               

              Working around really big heat exchangers, many don't have baffles. They create more restriction in the flow path and opportunities for vibration wear, which needs to be balanced against the additional gain in efficiency you may get. Nearly all are of the industrial design you initially linked to.

              IMO, baffles are totally overkill for a distiller. Worse comes to words you could simply add a couple inches to the length and you'd get the same efficiency.

              Most important with tube and shell hx's is to ensure a food 'fill' on the shell side. That is to say, ensure there are no air bubbles, much like bleeding a radiator. To that end,if you are going to have the inlet for cooling water on the top, and the outlet on the bottom, I recommend you put your flow control valve on the outlet. When starting the still run, close the outlet valve and fill the shell with water. When full, hook up your water source (with full hoses), turn on the water source, and only then crack open the outlet valve to control cooling flow.

              Hope that helps,
              RadicalEd

              Sent from Yahoo Mail on Android



              From: Zapata Vive <zapatavive@...>;
              To: <Distillers@yahoogroups.com>;
              Subject: Re: [Distillers] RE: Shotgun Baffle Design
              Sent: Fri, Oct 11, 2013 11:19:30 PM

               

              baffles are NOT necessary, in fact it seems very few use them.  I'm putting them in just because I know they can't hurt and I don't know exactly how much they'll help to decide if the (minimal) effort and material is worth the unknown performance gain.  I'm assuming baffles are helpful, or they wouldn't be in professional designs.  How well they work, what exactly they affect, and what their design parameters are seems to not have been studied in our hobby so far as I'm finding.

              Going off what have people proven to work, they aren't needed.  A completely made up number here, but from the builds I've looked at, I'd say 90% or more don't use baffles.  If you read someone just say they use a shotgun, I'd say they probably didn't build it with baffles.

              I wouldn't worry, 31 x 3/8" x 12" tubes seems like plenty to knock down 4 kw, it's comparable to a 31' liebig!


              On Fri, Oct 11, 2013 at 4:19 PM, <darylbender@...> wrote:
               

              Baffles? I'm just coming up the home stretch on a shotgun/firebox condenser (core approx 3" x 12") and now you have me wondering if it will work - I have no baffles. Pics below;


              http://surfin_dude.tripod.com/Condenser_02_Assembling.jpg

              http://surfin_dude.tripod.com/Condenser_03_The_Core.jpg

              http://surfin_dude.tripod.com/Condenser_04_Together_Unfinished.jpg


              It's going to be for a ~4KW pot still. It has thirty one 3/8" tubes through it inside the 3" body. Water is simply to go in at the bottom (side hose fitting) and out at the top. I can hold water inlet temp to 15C. There's about 2.35 sq in open area for the vapour to flow through.


              It took nuclear amounts of heat to solder it but I've since pressure tested it to about 60psi and it's good. Do you think channeling will be an issue?


               



              ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

              (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

              I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

              I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
              Image
              Of course it will be our standard single pass design instead of the double pass pictured there.

              Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

              Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

              I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

              If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
              Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
              I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

              I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

              Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
              shotgun endplate template 1 offset v8 (400x194).jpg
              shotgun endplate template

              Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
              I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

              I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...



            • Eddie Hoskin
              Oh, certainly the industrial info more more just as a FYI than really applicable to our scale.  It s a real different story when you re pushing a few
              Message 6 of 10 , Oct 17, 2013
              • 0 Attachment

                Oh, certainly the industrial info more more just as a FYI than really applicable to our scale. It's a real different story when you're pushing a few gigawatts thermal through a heat exchanger; vibes are a real issue then!

                But conversely, due the the smaller scale we deal with, the baffles will also add less to the efficiency, I think. Or at least it won't be really necessary at our scale; economics of 1-2% increased efficiency matters for industrial scale, but not so much for us :p.

                I would like to hear your calc numbers, though. No harm king learning for learning's sake!

                Radicaled

                Sent from Yahoo Mail on Android



                From: Zapata Vive <zapatavive@...>;
                To: <Distillers@yahoogroups.com>;
                Subject: Re: [Distillers] RE: Shotgun Baffle Design
                Sent: Thu, Oct 17, 2013 4:27:24 PM

                 

                Harry has been telling us this for years, but it really is all in the library.  So I dove in, took up The Heat Exchanger Design Handbook and did a lot of unnecessary calculations on baffle spacing for support and vibration reduction, all leading up to baffle spacing being pretty irrelevant on our small designs.

                But then amongst many other criteria, I did find that baffle spacing should be no more than shell diameter, and no less than 50mm regardless of other parameters.  So basically for a 2" nominal shell, 50-50.4mm spacing is best for flow considerations.  I posted a bit more in my thread on MD if anyone wants the specifics.

                And I'm not discounting what you're saying at all Ed, I just got curious why I've never seen anyone actually calculate the design or effect of baffles.  I don't really think vibration will be much of a concern for us, but I could be wrong.  Of the shotgun builds I've seen using baffles, none complained of vibration or noise, even one that used beer cans for the baffles!  So far as flow goes, I'll calculate it too if I can, test it if I can't, but I just don't see a few baffles 2" apart restricting flow even as much as the supply hose does.

                The air purging is a very good point though, and I think it's important for a lot of condensers.  angled liebigs purge readily, but my crossflow condenser for example doesn't always purge fully if I start flow while it's up in the air, so I've taken to starting the pump before I mount it, while I can put it at various angles with the ports facing up.

                Whether or not baffles are necessary, I'll actually calculate their effect.  I just got my hands on a fancy condenser calculator program, and should be able to run a standard design through with and without baffles if I can figure out all the other inputs properly....


                On Sat, Oct 12, 2013 at 7:26 AM, Eddie Hoskin <eddie_hoskin@...> wrote:
                 

                Working around really big heat exchangers, many don't have baffles. They create more restriction in the flow path and opportunities for vibration wear, which needs to be balanced against the additional gain in efficiency you may get. Nearly all are of the industrial design you initially linked to.

                IMO, baffles are totally overkill for a distiller. Worse comes to words you could simply add a couple inches to the length and you'd get the same efficiency.

                Most important with tube and shell hx's is to ensure a food 'fill' on the shell side. That is to say, ensure there are no air bubbles, much like bleeding a radiator. To that end,if you are going to have the inlet for cooling water on the top, and the outlet on the bottom, I recommend you put your flow control valve on the outlet. When starting the still run, close the outlet valve and fill the shell with water. When full, hook up your water source (with full hoses), turn on the water source, and only then crack open the outlet valve to control cooling flow.

                Hope that helps,
                RadicalEd

                Sent from Yahoo Mail on Android



                From: Zapata Vive <zapatavive@...>;
                To: <Distillers@yahoogroups.com>;
                Subject: Re: [Distillers] RE: Shotgun Baffle Design
                Sent: Fri, Oct 11, 2013 11:19:30 PM

                 

                baffles are NOT necessary, in fact it seems very few use them.  I'm putting them in just because I know they can't hurt and I don't know exactly how much they'll help to decide if the (minimal) effort and material is worth the unknown performance gain.  I'm assuming baffles are helpful, or they wouldn't be in professional designs.  How well they work, what exactly they affect, and what their design parameters are seems to not have been studied in our hobby so far as I'm finding.

                Going off what have people proven to work, they aren't needed.  A completely made up number here, but from the builds I've looked at, I'd say 90% or more don't use baffles.  If you read someone just say they use a shotgun, I'd say they probably didn't build it with baffles.

                I wouldn't worry, 31 x 3/8" x 12" tubes seems like plenty to knock down 4 kw, it's comparable to a 31' liebig!


                On Fri, Oct 11, 2013 at 4:19 PM, <darylbender@...> wrote:
                 

                Baffles? I'm just coming up the home stretch on a shotgun/firebox condenser (core approx 3" x 12") and now you have me wondering if it will work - I have no baffles. Pics below;


                http://surfin_dude.tripod.com/Condenser_02_Assembling.jpg

                http://surfin_dude.tripod.com/Condenser_03_The_Core.jpg

                http://surfin_dude.tripod.com/Condenser_04_Together_Unfinished.jpg


                It's going to be for a ~4KW pot still. It has thirty one 3/8" tubes through it inside the 3" body. Water is simply to go in at the bottom (side hose fitting) and out at the top. I can hold water inlet temp to 15C. There's about 2.35 sq in open area for the vapour to flow through.


                It took nuclear amounts of heat to solder it but I've since pressure tested it to about 60psi and it's good. Do you think channeling will be an issue?


                 



                ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

                (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

                I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

                I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
                Image
                Of course it will be our standard single pass design instead of the double pass pictured there.

                Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

                Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

                I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

                If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
                Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
                I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

                I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

                Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
                shotgun endplate template 1 offset v8 (400x194).jpg
                shotgun endplate template

                Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
                I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

                I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...



              • Zapata Vive
                Yeah, I really do appreaciate folks with experience in the real world. And I am having a great time learning about all of this. In fact, I think I can say
                Message 7 of 10 , Oct 17, 2013
                • 0 Attachment
                  Yeah, I really do appreaciate folks with experience in the real world.  And I am having a great time learning about all of this.  In fact, I think I can say I'm no longer scared to dive into condenser math, good texts and good calculators help alot!  Hopefully these calcs will be a help to all of us, but even if they end up not being worthwhile, they've elevated my ability to think about, understand and design my own equipment.  Either baffles are helpful, or not, but either way we'll know....

                  So I just finished crunching the numbers on Bc (Baffle cut, as a % of shell diameter).
                  I don't think attachments actually get through when I send group msgs via email, so the supporting info is in the thread in accesories at MD.

                  Basically found a graph with guidelines for baffle cut % compared to the ratio of central baffle length and shell diameter.  In the condenser I'm playing with baffle length came out right at 50mm as does shell diameter, so based on a Lbc:Ds ratio of 1:1 the suggested baffle cut % is 40-44%.

                  This relates to making a full ID baffle plate, measuring in 20-22mm and chopping off a slice.

                  Analysis of tube pitch layout coming, and then to make sure I can really use the calculator well enough to give meaningfull comparisons....
                • Zapata Vive
                  So I m playing around in my condenser calculator, and have some preliminary numbers. A couple points up front though. 1. This is a demo program, so I can t
                  Message 8 of 10 , Oct 17, 2013
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                    So I'm playing around in my condenser calculator, and have some preliminary numbers.  A couple points up front though.
                    1.  This is a demo program, so I can't change everything, this calc was done for a preset hydrocarbon vapor and water coolant.
                    2.  Baffles seem to be required, I can't really compare no baffles to the baffles designed above.

                    Anyway, I plugged in my designed shotgun, 12" long, 7x.5" OD tubes, 2" nominal shell, .5" coolant nozzles, 2" vapor/condensate nozzles, vertical orientation.   I gave it the preloaded hydrocarbon to condense, using water, specified a mass flow for both that seemed reasonable (weight equivalent of a 3000 watt stripping run for vapor and a coolant flow equivalent to 5 liters per minute), coolant in at 75*F and out at 120*F, so trying for a reasonable approximation of what we do.  Anyway, I'm looking for a comparison in design details though, not specific performance so I think the exact numbers are irrelevant to the differences. 

                    With the baffles I designed, 42% cut, 2" spacing this "condenser is rated as 89.966% over design and 133.576% over surface"
                    Same design but at 6" spacing "58.576% over design, 87.854% over surface"
                    Pretty significant difference there I'd say.

                    Since I have to define baffles, I tried to space them into irrelevance
                    Set baffle spacing to 12" and I get "36.484% over design, 57.629% over surface"
                    To confirm that, I try  letting it autocalculate the spacing if I define the baffle cut as 100%, same analysis.  So I think this is a relevant comparison to the optimized baffle.

                    Obviously 90% over design is better than 36.5% over design. 
                    All analysis was done with the same specified mass flow of condensate, which for us pretty much equates to a given power input.  It seems to me to imply the optimized baffle could handle 2.5 times as much power as no baffle.  If we ASSume that my approximated 3kw input was close and accept the analysis, then my design would max out around 5700 watts, while a standard shotgun would make it to just over 4kw.  Of course these numbers aren't accurate, but they should be relative.
                    Encouraging.

                    Of course I'm really new to all this, so consider this a hack job, not a scientific analysis at this point.  Any real engineer is more than welcome to help me out.  The design also ignores some real world facts like leakage around the baffles.  The design book addresses stuff like this, but the calculator I'm using doesn't.  Which means longhand analysis on stuff like that definitely isn't going to be done by me, but I do think I'll build it, which of course is where all this started and damn well oughtta be where it ends up!

                  • Zapata Vive
                    Clarification. I said my design could handle 2.5x as much power as no baffles, which isn t true. The power comparison I made does seem to be holding it s
                    Message 9 of 10 , Oct 18, 2013
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                      Clarification.  I said my design could handle 2.5x as much power as no baffles, which isn't true.  The power comparison I made does seem to be holding it's relevance though.  That means that a segmentally baffled shotgun should handle 40% more power than one without, all other things being equal.
                    • harisaki2004
                      From my experience I have the same design and use 17x 1/2 tubes (3/8 id) in 4inch diameter x 10 inches long and it knocks down 5 kW easily. I found that it
                      Message 10 of 10 , Oct 28, 2013
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                         From my experience I have the same design and use 17x  1/2" tubes (3/8 id)  in 4inch diameter x 10 inches long and it knocks down 5 kW easily.  I found that it would let vapour through, even with spirals added to the tubes.


                        However when I upped the power to 20kW I added 8" x 4" OD of 50 x 1/4 inch tubes underneath. That sold all issues and takes 20kWs easily.

                        regards

                        Hari.



                        ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

                        Working around really big heat exchangers, many don't have baffles. They create more restriction in the flow path and opportunities for vibration wear, which needs to be balanced against the additional gain in efficiency you may get. Nearly all are of the industrial design you initially linked to.

                        IMO, baffles are totally overkill for a distiller. Worse comes to words you could simply add a couple inches to the length and you'd get the same efficiency.

                        Most important with tube and shell hx's is to ensure a food 'fill' on the shell side. That is to say, ensure there are no air bubbles, much like bleeding a radiator. To that end,if you are going to have the inlet for cooling water on the top, and the outlet on the bottom, I recommend you put your flow control valve on the outlet. When starting the still run, close the outlet valve and fill the shell with water. When full, hook up your water source (with full hoses), turn on the water source, and only then crack open the outlet valve to control cooling flow.

                        Hope that helps,
                        RadicalEd

                        Sent from Yahoo Mail on Android



                        From: Zapata Vive <zapatavive@...>;
                        To: <Distillers@yahoogroups.com>;
                        Subject: Re: [Distillers] RE: Shotgun Baffle Design
                        Sent: Fri, Oct 11, 2013 11:19:30 PM

                         
                        baffles are NOT necessary, in fact it seems very few use them.  I'm putting them in just because I know they can't hurt and I don't know exactly how much they'll help to decide if the (minimal) effort and material is worth the unknown performance gain.  I'm assuming baffles are helpful, or they wouldn't be in professional designs.  How well they work, what exactly they affect, and what their design parameters are seems to not have been studied in our hobby so far as I'm finding.

                        Going off what have people proven to work, they aren't needed.  A completely made up number here, but from the builds I've looked at, I'd say 90% or more don't use baffles.  If you read someone just say they use a shotgun, I'd say they probably didn't build it with baffles.

                        I wouldn't worry, 31 x 3/8" x 12" tubes seems like plenty to knock down 4 kw, it's comparable to a 31' liebig!


                        On Fri, Oct 11, 2013 at 4:19 PM, <darylbender@...> wrote:
                         

                        Baffles? I'm just coming up the home stretch on a shotgun/firebox condenser (core approx 3" x 12") and now you have me wondering if it will work - I have no baffles. Pics below;


                        http://surfin_dude.tripod.com/Condenser_02_Assembling.jpg

                        http://surfin_dude.tripod.com/Condenser_03_The_Core.jpg

                        http://surfin_dude.tripod.com/Condenser_04_Together_Unfinished.jpg


                        It's going to be for a ~4KW pot still. It has thirty one 3/8" tubes through it inside the 3" body. Water is simply to go in at the bottom (side hose fitting) and out at the top. I can hold water inlet temp to 15C. There's about 2.35 sq in open area for the vapour to flow through.


                        It took nuclear amounts of heat to solder it but I've since pressure tested it to about 60psi and it's good. Do you think channeling will be an issue?


                         



                        ---In Distillers@yahoogroups.com, <distillers@yahoogroups.com> wrote:

                        (apologies for cross posting this here and at MD, hoping Harry or some of you other gurus might see it here)

                        I'm building a shotgun. 2" shell about 17" long (dictated by parts on hand, not design really). 7 x 3/8" nominal vapor tubes (1/2 OD actual).

                        I figure I might as well build it as well as I can, so I figure I'll put some baffle plates in to maximize efficiency. Like these:
                        Image
                        Of course it will be our standard single pass design instead of the double pass pictured there.

                        Figured I might as well ask if anybody knows any design criteria for the baffles? How many, ideal spacing, ideal amount of tube coverage etc. It seems like someone really smart would know things like an optimal baffle spacing in relation to shell ID, or maybe a function of flow rate or something. I don't know, do you? :confusion-confused: The only builds I've seen where people put in baffles, they just did and didn't discuss any design principles.  We've got equations, and better rules of thumb for everything from column diameter to condenser length, but what about shell and tube coolant baffle rules of thumb?

                        Right now I'm thinking I'll make them block about 2/3 of the ID of the 2" shell. Kinda seems right, but more conveniently because it lets me cut two of them from a plate cut from 2 inches of 3/4" nominal pipe.

                        I'm also thinking I'll make 4 baffles. Partly out of convenience (anybody seeing a pattern here?) and partly because I want my cooling water in and out on opposite sides of the shell. Don't really know why, I just do. I think. Well that would work with 4 baffles. Odd numbers of baffles are required to have in and out on the same side of the shell.

                        If I space 4 of them evenly over 17", there will be 3.4" between baffles. Does this matter? Is there a way to optimize it? I dunno.
                        Wikipedia says the baffles are usually attached to the tubes, not the shell to make maintenance easier. I plan to do this as well, more for ease of construction than god forbid I actually ever have to open it back up.
                        I also think a small space between the shell and plate will help prevent air pockets being trapped in the plates depending on the angle it is mounted. I'm assuming my baffles will be sloppy enough that this space will be there whether I aim for it or not, but if somehow I make perfect baffles I will file a small nick in the edge to let a little air bleed through.

                        I'm kind of hoping this shotgun will handle 5500 watts. Not that it's necessary, but it'd be nice. I'd really like it to handle 4500 watts comfortably.

                        Might as well throw this out here, though it doesn't relate to the baffles. This shotty will be run both vertically and at 45* angle. I know that most build perfectly flat plates or even concave them a bit to prevent any pooling/smearing on top of the condenser when run vertically. But I was thinking about how to minimize pooling when at 45*. I came up with moving one hole in the end plate right to the edge of the pipe, and bending a bit at the end to fit through the hole. Like this:
                        shotgun endplate template 1 offset v8 (400x194).jpg
                        shotgun endplate template

                        Note the upper right hole is closer to the edge. It's not right at it because I anticipate having to file it out a bit wider to make the vapor tube fit through at an angle. anyway, if the condenser is mounted at a 45* angle so the offset tube is at the bottom, there will be a much smaller pool there. If I get it right to edge of the shell, then the maximum pool depth would be the thickness of the vapor tube pipe.
                        I'm thinking I will make one plate like that, and the other plate with a slight concave-ity-ness-ification. That way I can switch it end to end if running vertical or angled.

                        I know, I may be over thinking the straightforward shotgun, but it's the little design details you think of after the fact that have you melting more solder later to get it just right, and I'm just trying to get them right first go...

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