Announcement

Collapse
No announcement yet.

Bezzera Duo DE Dual Boiler

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #46
    I’m sorry but temperature, volume and pressure are correlated and the statement “Whether the boiler expands or not doesn't matter to the relationship between temperature and pressure.“ is not correct.

    In theory you could design a boiler of variable volume which maintains constant pressure, so that when the temperature rises the boiler expands and the pressure doesn’t increase.

    I appreciate that all coffee machines have a relatively rigid boiler so the (approximately) linear relationships between pressure and temperature is normally implicitly assumed, but from a general physics perspective the statement “The relationship between temperature and pressure in a boiler is essentially linear.“ is true only if the boiler is rigid (fixed). So Mike’s statement was factually correct.

    Comment


    • #47
      Also, Mike’s comment about potential discrepancies between measured and calculated pressure is also correct. The relationships between temperature and pressure used for the computation is only valid in stationary conditions, so as soon as the steam tap is opened the calculated pressure might be no longer accurate.

      Comment


      • #48
        Blackfish, we are discussing the relationship between temperature and pressure. Yes changing the volume of the boiler will affect the temp/pressure, but it does not affect the relationship between the temperature and pressure! Which is what we are discussing and are concerned with.

        At a temperature of T1 the pressure will be P1
        At a temperature of T2 the pressure will be P2
        At a temperature of T3 the pressure will be P3
        etc...

        This is true no matter what the volume of the boiler is. Whether the boiler is 1L in size or 10,000L in size if its temp is T2 then its pressure will be P2. Not P1 and not P3 or any other Px other than P2. That is the relationship under discussion and volume does not enter into that relationship. If you are told what the temperature of the boiler is you can state what the pressure is and visa-versa. If you're given the pressure of the boiler you can state what the temperature is. Volume does not enter into the discussion at all.

        Graph out Temperature vs Pressure for temperatures between 100C and 130C, there's the linear relationship under discussion. You can change the volume of the boiler all you want and nothing on that graph will change. Everything on it will be just as true in the new boilers you made as it was in the original boiler. It is that graph and the relationship between the two axis that is under discussion.


        Java "Definitions matter!" phile
        Toys! I must have new toys!!!

        Comment


        • #49
          I have never stated that the relationship changes if the given size of a rigid boiler changes.

          You seem to miss the point I’m trying to make, that for what you say to be true the boiler needs to be fixed/rigid/of constant volume, or however you want to define it.

          A boiler which maintains the pressure constant rather than the volume can easily be built. Imagine a cylinder full of water with a sealed but freely sliding piston at the top of 10 square inches area and weighing 200 pounds. The pressure of the water in that boiler will be 20 psi no matter what the temperature is: 10, 50, 100 Celsius or more, it does not matter. In my newly designed boiler, which I’m going to patent tomorrow:
          T1 pressure equals 20 psi
          T2 pressure equals 20 psi
          T3 pressure equals 20 psi
          in substance, there is no relationship between temperature and pressure.

          So I reiterate that the linear relationship between temperature and pressure is only valid if the boiler is rigid, as Mike said. A variable volume boiler would not necessarily maintain that relationship.

          I apologise for boring the hell out of everyone else following this thread and I’m going to leave it here because I think there is nothing else I can say to make my concept clearer.

          Comment


          • Javaphile
            Javaphile commented
            Editing a comment
            Remember we are dealing with a saturated steam boiler here. Your newly patented boiler isn't a saturated steam boiler until it hits ~125.97C which is the boiling temperature of water when it is under 34.7psia (Pounds per Square Inch Absolute ie atmospheric pressure plus gauge pressure, 14.7psi and 20psi in this case.). The T1=P1, T2=P2 etc is only true in a saturated steam environment. Hence any temp/pressure comparisons using temps below ~125.97C are meaningless as the boiler is not in a saturated steam environment yet. At that temp of ~125.97C your boiler would be in stasis at 20psi indicated on its pressure gauge and the 200 pound sitting unmoving in the cylinder.

            But....

            With your newly patented boiler what happens when you set the PID controlling the temperature of the water too 126C or higher? Because of your open top cylinder the pressure can never rise above 20psi, (Actually it could if the cylinder were tall enough and your instruments sensitive enough.) which means the water can never reach a temperature of 126C or higher. So the heater coil happily boils more and more water turning it into more and more steam in an attempt to reach it's unachievable set point. That steam has to go somewhere so it expands, never rising above 20psi, in the cylinder pushing the 200 pound weight higher and higher until finally pushing the weight completely out of the cylinder. At which point the gauge drops to 0psi, and you get a big flash of steam.

            Far from disproving the relationship between temperature and pressure which exists independently from volume in a saturated steam boiler your 'newly patented boiler' actually proves it. It is a saturated steam boiler only when it is at a temp/pressure of 125.97C/20psi. Below that temp the water is not boiling, hence there is no steam. And because of its open top its pressure can not rise above the 20psi and because its pressure can not rise its temperature can not rise. No matter how much energy you put into the water its temp will not rise above the 125.97C, only more steam will be produced expanding the volume of the boiler as it pushes the weight up the cylinder. Changing the volume dramatically, all the while never changing the temp/pressure with-in the boiler. Right up until the weight is pushed out the top of the cylinder.

            The T1=P1, T2=P2, T3=P3 holds true in your boiler the same as any other saturated steam boiler. The only difference is your boiler only has a single operating temp/pressure where-as most boilers have a range. But that 125.97C/20psi is the same temp/pressure condition that will be found in any other saturated steam boiler.


            Java "Fun with Physics" phile

        • #50
          Originally posted by Blackfish View Post
          Also, Mike’s comment about potential discrepancies between measured and calculated pressure is also correct. The relationships between temperature and pressure used for the computation is only valid in stationary conditions, so as soon as the steam tap is opened the calculated pressure might be no longer accurate.
          It all depends on the data being used in the calculation. If the Set_Point_Temp is being used then it is displaying a static number that is would only be valid under your "stationary" conditions. However as I commented in a previous post:
          Originally posted by Javaphile View Post
          If the Duo is using the measured boiler temp in its calculation you know the actual boiler pressure.
          Depending on the PID's polling and calculation interval the displayed pressure may be as little as a thousandth of a second behind real time, or minutes behind it if they got lazy/cheap in their programming/hardware.


          Java "Something to ask the manufacturer" phile
          Toys! I must have new toys!!!

          Comment


          • #51
            Well...that was a robust and informative discussion. Thanks folks. Between that and my trying to stuff a Thermocouple into the PF and my experience thus far, I can say that it has only increased my confidence in the reasonable accuracy of the temperature and pressure gauge readings in the DUO DE.

            Performance: Steam pressure, Big Tick. Hot water supply, Tick. Ability to set the parameters for the brew, Big Tick. Ability to freestyle, a la E61 lifting the lever....in this case, by pressing the manual button instead, Big Tick. Personal satisfaction with the machine Huge Tick.

            Mine has the water plumbed in. Very convenient. It can never be a Profiling machine, so if you need that functionality you will need to look elsewhere.

            I start mine with a smartswitch. By doing this, it bypasses the inbuilt programming ability but means it switches to standby after 30 minutes without use. I just touch the screen, to wake it, and within a few minutes, as quick as boiling a par-filled kettle, it's ready to go. I'm very relieved to NOT have buyers regret with the DUO.

            Now, it's up to Bezzera to provide appropriate support to the support technicians to ensure firmware updates and improvements are made available in the future. [However, I strongly suspect Mr Bezzera wouldn't be interested in providing the same aftermarket improvements that John does at Decent!] ie it is has the inherent capability to be more flexible in its programming and the display could be tweaked for better readability. eg slightly wider bars and gauges by reducing the unnecessary Logo taking up screen real estate. When the boiler is heating, advising where temperature is up to and not the target temp. [it does do this when it is first switched on] But, these are minor tweaks in the scheme of things.

            Comment


            • #52
              Originally posted by quester View Post
              Now, it's up to Bezzera to provide appropriate support to the support technicians to ensure firmware updates and improvements are made available in the future. [However, I strongly suspect Mr Bezzera wouldn't be interested in providing the same aftermarket improvements that John does at Decent!] ie it is has the inherent capability to be more flexible in its programming and the display could be tweaked for better readability. eg slightly wider bars and gauges by reducing the unnecessary Logo taking up screen real estate. When the boiler is heating, advising where temperature is up to and not the target temp. [it does do this when it is first switched on] But, these are minor tweaks in the scheme of things.
              They won't. It's been confirmed to me a few times that Bezzera are not looking to develop firmware updates beyond the original release for fixing first run glitches. Pretty ridiculous really.

              I own a Matrix DE (discontinued now) and have all the same issues. Will probably be looking to sell the machine at some point and move on to something else.

              Comment


              • Martino
                Martino commented
                Editing a comment
                noidle22, what are the issues you are referring to with your Matrix? Can you list them pls?

              • noidle22
                noidle22 commented
                Editing a comment
                1. Inbuilt water tank low water alert is way too soon, alerting when there's still about 1.5L left. It will also cut the shot and stop all operations when it senses this.
                2. Pressure gauge is useless. Adjust it with a blind to what seems to indicate correctly, during a shot it will swing from 6-10 bar erratically.
                3. The auto start was turning the machine on at random points during the night/early morning. Can't know when, it was just on sometimes well before I'd set it to. I just stopped using the timer.
                4. Shot counter is stupid, it takes every press of the buttons, no matter how long, as a shot. I flush the machine before use then 3-4 times after the shot so for every 1 shot I actually make, the machine registers 7 or 8 "shots". Thus the counter shows 5200 shots when I've really only done 1500 or so. Why didn't they do what Breville did and make it count only after 7 or so seconds?
                5. Pre-infusion is not pre-infusion as advertised, it's just wetting.
                6. Anti-vac vents into the case. Observed visible condensation on the sides, for a machine with so much electronics, I don't think this is wise.
                I installed an anti-vac which diverts to the tray soon after noticing this.
                The large amount of complaints of water in the screen may have been attributed to this. I have a first release machine and have never had any LCD issues.

                There may be some more niggling issues but those are the main ones. The machine does make great coffee (would be better with pre-infusion though to tame the rotary pump) and has excellent steam, no complaints there.

                I may be a bit harsh on it but this is a flagship machine at a price point competing with many established, popular machines. It should have been better.

            • #53
              Hi Quester,

              I see you're using a smart switch to control your machine. You also have it set to auto-standby after 30 minutes. You can choose if you want to have auto-standby or not (even if you're not using the internal timers). In the settings, turn the Auto-Timer to On, even though you have no timers set. Doing that overrides the Auto-Standby and the machines stays on. That's how I run it. I can always put the machine into Standby by pressing the display and pressing the Standby button. Cheers.

              Comment


              • quester
                quester commented
                Editing a comment
                Excellent!! Thanks Mike.

            • #54
              Originally posted by noidle22 View Post
              1. Inbuilt water tank low water alert is way too soon, alerting when there's still about 1.5L left. It will also cut the shot and stop all operations when it senses this.
              2. Pressure gauge is useless. Adjust it with a blind to what seems to indicate correctly, during a shot it will swing from 6-10 bar erratically.
              3. The auto start was turning the machine on at random points during the night/early morning. Can't know when, it was just on sometimes well before I'd set it to. I just stopped using the timer.
              4. Shot counter is stupid, it takes every press of the buttons, no matter how long, as a shot. I flush the machine before use then 3-4 times after the shot so for every 1 shot I actually make, the machine registers 7 or 8 "shots". Thus the counter shows 5200 shots when I've really only done 1500 or so. Why didn't they do what Breville did and make it count only after 7 or so seconds?
              5. Pre-infusion is not pre-infusion as advertised, it's just wetting.
              6. Anti-vac vents into the case. Observed visible condensation on the sides, for a machine with so much electronics, I don't think this is wise.
              I installed an anti-vac which diverts to the tray soon after noticing this.
              The large amount of complaints of water in the screen may have been attributed to this. I have a first release machine and have never had any LCD issues.

              There may be some more niggling issues but those are the main ones. The machine does make great coffee (would be better with pre-infusion though to tame the rotary pump) and has excellent steam, no complaints there.

              I may be a bit harsh on it but this is a flagship machine at a price point competing with many established, popular machines. It should have been better.
              noidle22,
              items 2,3,4 sounds like that machine has a fault, something in its processor has failed, if you are still under warranty, I'd get it fixed, those things are definitely wrong.
              Item 1 sounds a bit weird too but isn't it a function of where the sensor for the tank is physically located? Or are you saying that it thinks you are out of water and shuts off yet when you look in the tank the water level is above the sense point?
              You did the right thing with the anti-vac line, it should drain into the drip tray.

              Comment


              • #55
                Originally posted by Martino View Post

                items 2,3,4 sounds like that machine has a fault, something in its processor has failed, if you are still under warranty, I'd get it fixed, those things are definitely wrong.
                The pressure gauge problem is an issue that affects all of them, nothing I can do. I agree the timer is a problem, I was just lazy and didn't address it. Regarding the shot timer, it seems to be just how it works, it registers a press of the button as a shot. Don't think there's much that can be done about this.

                Item 1 sounds a bit weird too but isn't it a function of where the sensor for the tank is physically located? Or are you saying that it thinks you are out of water and shuts off yet when you look in the tank the water level is above the sense point?
                The sensor level is just too high, way above the actual outlet of the water tank. It's a capacitive sensor and the machine has a sensor calibration function. Doesn't matter how many times I calibrate it or what sort of water is in the tank, the result is the same. I do have it plumbed in now so it's not a pressing concern but when i had it running on the tank it was annoying.

                You did the right thing with the anti-vac line, it should drain into the drip tray.
                It's bizarre why they didn't include it as standard given what you pay for the thing.

                Comment


                • quester
                  quester commented
                  Editing a comment
                  noidle22, hope I haven't missed what you have already stated, but, as I understand it, the shipments late 2019 onwards, had the firmware and fixes sorted that plagued the earlier machines. If yours was earlier 2019 I guess it may be out of warranty. However, given that batch was 'faulty' would the retailer still service it with these upgrades for you? (perhaps under something like a Consumers Guarantees Act?)
                  Issues like those listed can sure sap some of the joy out of the machine for you
                  Re the Bar pressure during shots, I would prefer the gauge didn't swing in half barr increments. but it is near enough for me to get the gist as to whether I have ground too coarse or fine and whether I might have channeling.

              • #56
                It would be great to have some commentary from Jetblack Espresso or other Bezzera service agents with regards these issues noidle22 is experiencing. I think it's important that Bezzera provide good support to their agents. So far, that support seems limited.

                Comment


                • #57
                  Originally posted by quester View Post
                  It would be great to have some commentary from Jetblack Espresso or other Bezzera service agents with regards these issues noidle22 is experiencing. I think it's important that Bezzera provide good support to their agents. So far, that support seems limited.
                  I actually am a Bezzera service agent, I just do very low volumes. As is per normal, my own equipment usually gets neglected after I've spent all day on other people's stuff.

                  My machine is a 2018 build. I will get around to doing the software update one day and see what that may resolve. Certainly if I sell the machine it will be done.

                  Comment


                  • #58
                    Originally posted by noidle22 View Post

                    I actually am a Bezzera service agent, I just do very low volumes. As is per normal, my own equipment usually gets neglected after I've spent all day on other people's stuff.

                    My machine is a 2018 build. I will get around to doing the software update one day and see what that may resolve. Certainly if I sell the machine it will be done.
                    Ugh - plumbers classic. They fix everyone else's pipes but their's leak. I hear ya :-) Well, at least you know what's wrong and what you can do about it. So, you said at some point you will be looking to sell your Matrix, right? What are the possible contenders for the new machine then?

                    Comment


                    • #59
                      Hi Noidle22
                      Your observations about your Matrix are all good points. The shot counter operating for every time you operate the pump is a bit clumsy. I probably run the group about three times per coffee shot. The electronic reminder to back-flush is very handy, so I just set the shot counter to 300 so I back-flush every 100 shots. I have measured the group pressure with a portafilter gauge and compared it to the Duo display. While the Duo pressure indication moves around, its 'average' reading is spot on to an analogue gauge. The issue here might be a lack of a smoothing time constant on the pressure transducer which could be easily fixed in firmware. Of course we all understand that analogue gauges immersed in glycerine are very slow acting and won't jump around even of the actual pressure does. Who knows with the natural changes of puck resistance from dry to wet, from compacted to expanded and then extracted, the puck resistance does change quite a bit over the extraction period, so the Duo and Matrix changing pressure readings might be right!!!

                      The overall brilliant feature of the Duo IMHO is the BZ head. You can pay $12,000 to $16,000 for a La Marzocco or Slayer to get a huge fully-saturated head (or a Rocket Nine One for $10,000). They are big and it is expensive to fabricate such a substantial stainless steel jacket to maintain the boiler temperature around the head. Because they are large, they need single bigger boilers, bigger heating elements and take a lot longer to reach temperature stability. All this because they are using water as the medium to move heat/energy to the group head. The PID controller (probably with an offset) in these machines must maintain the optimum balance between boiler temperature and head temperature, but this might involve some compromise. Compared to the BZ head, this is so old-school and clumsy.

                      The BZ uses electrical energy to move heat to the group head (as opposed to hot water) by a 120W double heating element controlled by its own PID. It's smaller, more efficient, means you can have a tiny (0.75L) coffee boiler and it heats up super fast. It's much cheaper and smaller to transport heat/energy over electrical wires compared to hot water through stainless steel jackets. Dare I say it, I'm sure that the BZ head has better temperature stability due to group head having it's own dedicated PID while the boiler has its own separate PID. This means if the head cools, it heats the head only. So no offsets needed. Brilliant. On this basis, with all the other minor gripes about the machine, makes the Duo for me, "Best In Class".

                      Comment


                      • Martino
                        Martino commented
                        Editing a comment
                        Well said mike! Those are some of the reasons I was interested in the Duo DE in the first place. Had it been on the market just a year earlier, I would have had it in my kitchen.

                    • #60
                      Originally posted by mikef View Post
                      The overall brilliant feature of the Duo IMHO is the BZ head. You can pay $12,000 to $16,000 for a La Marzocco or Slayer to get a huge fully-saturated head (or a Rocket Nine One for $10,000). They are big and it is expensive to fabricate such a substantial stainless steel jacket to maintain the boiler temperature around the head. Because they are large, they need single bigger boilers, bigger heating elements and take a lot longer to reach temperature stability. All this because they are using water as the medium to move heat/energy to the group head. The PID controller (probably with an offset) in these machines must maintain the optimum balance between boiler temperature and head temperature, but this might involve some compromise. Compared to the BZ head, this is so old-school and clumsy.

                      The BZ uses electrical energy to move heat to the group head (as opposed to hot water) by a 120W double heating element controlled by its own PID. It's smaller, more efficient, means you can have a tiny (0.75L) coffee boiler and it heats up super fast. It's much cheaper and smaller to transport heat/energy over electrical wires compared to hot water through stainless steel jackets. Dare I say it, I'm sure that the BZ head has better temperature stability due to group head having it's own dedicated PID while the boiler has its own separate PID. This means if the head cools, it heats the head only. So no offsets needed. Brilliant. On this basis, with all the other minor gripes about the machine, makes the Duo for me, "Best In Class".
                      The whole point of a saturated group head is that it is at exactly the same temperature as the boiler, because it is essentially in the boiler. The reason offsets are required are because the hot water coming out of the boiler travels through small pipes with large surface areas and lose significant heat. The pickup pipe for the saturated group is down within the boiler but it travels through the 'arm' of the boiler going to the group. There might be a degree difference between the dead centre of the big part of the boiler and the group, or there might not. Given that the 'arms' of the boiler come off the main boiler in an upwards direction to the group heads I'm inclined to think that natural convection will reduce temperature differences to tenths of a degree. The huge thermal mass of all the water in the boiler and all the metal the boiler is made of will provide greater temperature stability than a cartridge heating element in a group head. That being said, I would argue you are correct that a cartirfge heater is a more efficient way to heat up a domestic machine with a single group and small boiler. Not trying to bash the Duo/Matrix here, it just sounds like you're trying to justify your machine choice and working backwards to some questionable engineering.

                      Comment

                      Working...
                      X