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  • #16
    Re: Thermoblock versus Boiler

    Just remember everyone, that you cannot compare the new Sunbeam EM6900 to any other TB machine. It is head and shoulders above them all, IMO. If you are comparing it as if it was a normal TB machine you are going to be way out with your assumptions.

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    • #17
      Re: Thermoblock versus Boiler

      Originally posted by Monti link=1118073813/0#13 date=1121160501
      So, then how do you explain that I can open the steam up full power and it just never slows or looses power at all.  It just keeps on frothing as long as I like.  A thermoblock is creating the steam as well as a thermoblock heats the water for the coffee.
      Monti, when it comes to the separate steam thermoblock I would guess that Sunbeam got it right. For that particular job all you need is a temp over 100C. How far over doesnt matter. If you have a block of metal and a big enough electrical element you can steam all night! Just ask anyone who uses a steam iron (even a Sunbeam one ;D) .

      But the espresso shot is another matter. For espresso you need stable temperature, not a minimum temperature. And that is where thermoblocks inevitably fall down. Please dont get me wrong - the Sunbeam may deliver a decent AVERAGE temperature through a coffee shot, but proper extraction depends on consistency to minimise the burnt and sour tastes that come from temps that are respectively too high and too low.

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      • #18
        Re: Thermoblock versus Boiler

        Originally posted by ShortBlack link=1118073813/15#16 date=1121161410

        Monti, when it comes to the separate steam thermoblock I would guess that Sunbeam got it right.  For that particular job all you need is a temp over 100C.  How far over doesnt matter.  If you have a block of metal and a big enough electrical element you can steam all night!  Just ask anyone who uses a steam iron (even a Sunbeam one  ;D) .

        But the espresso shot is another matter.  For espresso you need stable temperature, not a minimum temperature.  And that is where thermoblocks inevitably fall down.  Please dont get me wrong - the Sunbeam may deliver a decent AVERAGE temperature through a coffee shot, but proper extraction depends on consistency to minimise the burnt and sour tastes that come from temps that are respectively too high and too low.
        Except, if you have a certain size of block of metal big enough and you know how much it will heat the water if it passes through it at a certain speed and volume then you have the temp controlled.  Dont think of it as the heating element heating the water inside of it and when it starts pumping itll have new cold water passing through it.  Rather, IMO, it has no hot water inside and the same temp water passes thorough it at constant speed and volume, so the temp of evey drop should be the same from start to finish.  

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        • #19
          Re: Thermoblock versus Boiler

          Originally posted by Monti link=1118073813/15#17 date=1121162268
          Rather, IMO, it has no hot water inside and the same temp water passes thorough it at constant speed and volume, so the temp of evey drop should be the same from start to finish.  
          Monti, any thermoblock would be empty at the start of a shot. Thats not the issue. Regardless of the speed and volume, the start of the shot will be hotter than the finish because the water draws heat from the metal as it passes through. The last 30 mls will have less heat to draw from the metal because it has been cooled by the first 30, and the metal wont have had the time to recover the right temperature.

          Ive pretty much said all I can to describe a thermoblock to you! Having said that, if your Sunbeam makes you a good cup of coffee then all is well and you should enjoy your purchase.

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          • #20
            Re: Thermoblock versus Boiler

            wouldnt the elements be on during the pour thus canceling out to a certain extent the temp dorp caused by the cool water comming in?

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            • #21
              Re: Thermoblock versus Boiler

              Rich:

              It is difficult to say what is happening in the thermoblock.

              It is a real balancing act dependent on flow rate, heating rate of thermoblock, thermal mass of the thermoblock, reaction time of the thermocouple to changing temperature and the logic it uses to control temperature.

              I still think it is an incredibly difficult tightrope to walk. In an ideal world you would have instant energy and instant response to changes in temperature. In reality the logic in the microprocessor will do a lot of prediction based on less than instant response times of the thermocouple to varying flowrates (which it can only estimate from temperature changes), the thermoblock cant transfer heat instantly either so it is all rather approximate.

              The boiler is a sledgehammer approach to this delicate balancing act which works! ie. low tech, brutal, somewhat inefficient but very effective and stable.

              I guess we will see just how clever Sunbeam is over the next few weeks or months as interested techies do their own measurements.

              Grant

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              • #22
                Re: Thermoblock versus Boiler

                Originally posted by wattgn link=1118073813/15#20 date=1121175001
                It is a real balancing act dependent on flow rate, heating rate of thermoblock, thermal mass of the thermoblock, reaction time of the thermocouple to changing temperature and the logic it uses to control temperature.
                Grant
                Hi All,

                I dont believe that it is an all that difficult task to overcome... given that the design would have to take into account the variables that effect the outcome and then have a suitable control mechanism to deliver the desired outcome.

                Im sure Sunbeam and many other companies have the where-with-all to successfully achieve such a design and its implementation. The actual physics involved is minuscule in comparison to that of many other appliances, its the economies of scale that will determine how far companies like Sunbeam are prepared to go in order to satisfy the wants and desires of hobbyists such as ourselves.

                Cheers,
                Mal.

                Comment


                • #23
                  Re: Thermoblock versus Boiler

                  Mal:

                  Well, I dont agree with you at all on that point.

                  Well see though, you could be right but up until this point in time, thermoblocks havent delivered for all the reasons just discussed.

                  Microprocessors help for sure to work all this stuff out. At the end of the day though it is old fashioned thermocouples and pumps and heated thermoblocks which have to do the work.

                  You could look upon the boiler as just being a very large thermoblock, one where all the balancing and timing issues are ironed out by the thermal mass in the boiler.

                  The thermoblock you could look upon as being a very small boiler, which is pretty well what it is.

                  I suspect that thermoblock technology may be good enough for the average consumer but Id be very surprised if it matches the performance of a good boiler.

                  I was just thinking about the last time we used the commercial machine at Supreme Coffee Machines. One of the things I noticed was the tendency to easily burn coffee. You have to be so careful not to let that group heat up. Tricky. Boiler machines still seem to be the best solution to good temperature control especially with good PID/microprocessor control built in.

                  Well soon see.

                  Grant

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                  • #24
                    Re: Thermoblock versus Boiler

                    There is nothing innate to the Thermoblock system that makes it inferior to the Heat Exchanger based system. In point of fact the Thermoblock type system is capable of better control and more effeicient use of energy than the HX type system. *If youre willing to pay the bucks required to build such a system.

                    The shortcomings we see in the TB based systems are not with the principles of TB systems but rather in their application.

                    Whats that you say? "You can claim thats the case but wheres the proof? Theres not a single TB based system out there with great thermostability!"?

                    Perhaps not in the espresso world. In the science world however such systems have been around for decades. *Every high-end piece of lab equipment I have seen made with-in the last 20 years that needs to heat a solution up for testing purposes uses guess what, thats right, a Thermoblock type system.

                    Most of these systems have a thermo-stability measured in tenths of a degree with some Ive seen being as accurate as +/- 3/100ths of a degree F. with the newer ones probably accurate to a hundreth of a degree or better by now.

                    Due to the very nature of their design (assuming of couse that its actually *built to be capable of it) Thermoblocks are in point of fact more thermally stable and more controllable than Heat Exchanger based systems. Both theory and physical application proves it beyond any shadow of a doubt.

                    Just because a machine is a Thermoblock does not automatically make it inferior to a Heat Exchanger based system.

                    Yes, based on what weve seen in the past for TB based systems in the espresso world it *probably is, but it might not be.

                    Eventually someone is going to put the needed engineering into a TB based espresso machine that will give it thermal stability like nothing weve ever seen before in the espresso world, but that lab workers have been seeing every day for decades and take for granted.

                    Before we rip on a new Thermoblock based machine lets give it a chance to prove itself. Who knows, perhaps somebody finally got it right.

                    Java "First test, *then decide!" phile
                    Toys! I must have new toys!!!

                    Comment


                    • #25
                      Re: Thermoblock versus Boiler

                      Originally posted by ShortBlack link=1118073813/15#18 date=1121165589
                      Monti, any thermoblock would be empty at the start of a shot.  Thats not the issue.  Regardless of the speed and volume, the start of the shot will be hotter than the finish because the water draws heat from the metal as it passes through.  The last 30 mls will have less heat to draw from the metal because it has been cooled by the first 30, and the metal wont have had the time to recover the right temperature.

                      Ive pretty much said all I can to describe a thermoblock to you!  Having said that, if your Sunbeam makes you a good cup of coffee then all is well and you should enjoy your purchase.
                      I have to disagree with you and also with Wattgn, and agree with Rich and Rae.

                      Guys, look at it this way:
                      I you send water with a constant speed and volume down a pipe that is heated all the way through, then at the end of it every drop of the water will be the same temperature if the pipe is long enough, regardless you send chilled or room temperature water. If you want to control the temperature at the end of the pipe even with different temperature waters going into the pipe, all you have to do is to make the pipe longer. If the pipe is so long that the water is reaching the required temp by half way up the pipe, then the water just travels on from there, at the same temp, till the end. If the water starts out colder, then it will just travel further up the pipe before it reaches the required temp, and then just travels on the same to the end of the pipe.

                      Not so difficult at all and no microprocessors needed with fast adjusting ability. All is needed is constant speed of water (pump), constant volume (diamatre of pipe or tubing) and an appropriate length of pipe or distance for the cold water to travel. They are all easy to achieve with primitive and cheap techology.
                      The reason it hasnt been done is because there hasnt been a need for them to build one. People havent been asking for them. There hasnt been much competition for this type of machine, etc.

                      Comment


                      • #26
                        Re: Thermoblock versus Boiler

                        Im sure thermoblocks can ultimately work as well as, if not better than boilers. Whether they can do so economically is another question. Lets face it, coffee machines use the simplest technology (large thermal inertia) to achieve their goal. But large thermal inertia has its disadvantages such as inability to respond to change. Using the KISS principle (Keep It Simple Stupid), the boiler machines are the way to go. For exquisite control of water temperature using feedback, boilers would not be the best.

                        One point with boilers is that if the cold feed water introduced during a shot mixes efficiently with the boiler water, it will inevitably lower the brew temperature. If it doesnt mix efficiently, then the boiler temp can remain approximately constant provided the cold feed water remains segregated from the water delivered to the group. So its a matter of intelligent design, not just size. It also not just a matter of the thermal inertia of the system, its also and primarily based on the fact that water has poor thermal conductivity and so if it doesnt mix efficiently, it will remain segregated, producing cool spots within the boiler.

                        One point with thermoblocks is that they must be hotter than brew temperature to ensure rapid heating of the flowing water. That means the water in the thermoblock at the start of a shot will be hotter than brew temperature. So thermoblock inevitably starts out hot and ends cold. The total temperature variation depends on the design.

                        Bare in mind that Quickmill have been building high quality thermoblocks for years. Ive heard that the new Sunbeam TB may be based on the Quickmill design.

                        PS I agree mostly with Montis statement above. However, it is more complicated than that as as the water heats up it cools the TB, which must be heated to compensate. As a TB thermostat is only measuring the temperature at one point it will average the heat lost and not be able to compensate accurately. However, with a known flow rate and some electrickery, you could pre-program the heating element to provide optimal heating for the load. Ultimately the Sunbeam is just an electronic HX machine. HX machines work pretty well, but have enough stored energy to heat the 30-60 ml of water required for a shot. The TB just has to apply this energy with the heating element. So if a HX machine works, so can a TB.

                        Dont judge the ultimate performance of a TB on the performance of cheap TB machines. Theyre cheap for a reason.

                        Comment


                        • #27
                          Re: Thermoblock versus Boiler

                          Sigh. I should have given up by now.

                          Monti, lets just simplify things and say that espresso brews at 92C. Youre just assuming that a long pipe heated to 92C will give you water at 92C. But it doesnt work like that.

                          Heat exchangers need to be hotter than 92C so that water, travelling at a given volume and rate, will reach 92C. Thermoblocks (being a type of heat exchanger) have to be hotter in the hope that the water will heat to 92 as the metal cools (i.e. "exchanges" its heat with the water). This is why the boiler in commercial HX machines is always at steaming temperature, while the espresso pipe that runs through that boiler outputs water at 92C. If you cant grasp that, you may as well stop reading now.

                          Now the perfect thermoblock would be at the right temperature to heat the whole shot to 92C, so that the block and the water would both end up at that exact temperature. But here comes the problem. To do that, the water needs to be sitting still and not moving through (like, for example, in a boiler).

                          You also assume that a thermoblock will contain just enough water for the coffee shot and no more. Have you wondered how water is pushed through a thermoblock and into your portafilter? Answer: with a pump. What does the pump use for pressuring the coffee shot through? Answer: more water from the tank.

                          Enough said.

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                          • #28
                            Re: Thermoblock versus Boiler

                            Actually if the HX were at the brew temperature it would take an infinitely long pipe for the water to reach brew temperature, as the rate at which heat flows is proportional to the difference in temperature. Thats why HX machines work over a range of flow rates, not for all flow rates.

                            Comment


                            • #29
                              Re: Thermoblock versus Boiler

                              Originally posted by ShortBlack link=1118073813/15#26 date=1121215722
                              Heat exchangers need to be hotter than 92C so that water, travelling at a given volume and rate, will reach 92C.  Thermoblocks (being a type of heat exchanger) have to be hotter in the hope that the water will heat to 92 as the metal cools (i.e. "exchanges" its heat with the water).  This is why the boiler in commercial HX machines is always at steaming temperature, while the espresso pipe that runs through that boiler outputs water at 92C.  If you cant grasp that, you may as well stop reading now.
                              Heat exchangers do have to work like that as they heat the water in the heat exchanger which is further away from the group head. How far is a HX in an average machine? It is in the middle of the huge boiler. Is it not? While the TB is righ at the mouth of the portafilter in comparison. It is impossible to place a HX close enough to the group head. You have to forget the notion that TB machines work exactly like HX machines. On the surface they do, but in reality there are a lot of differences. Maybe you cannot grasp that? - just to be rude like you in my expressions. Except that I feel bad about being rude.

                              Now the perfect thermoblock would be at the right temperature to heat the whole shot to 92C, so that the block and the water would both end up at that exact temperature.  But here comes the problem.  To do that, the water needs to be sitting still and not moving through (like, for example, in a boiler).
                              The water wouldnt have to be still at all. It can be moving and being heated at the same time. Is it not? Is it such a crazy idea?

                              You also assume that a thermoblock will contain just enough water for the coffee shot and no more.  Have you wondered how water is pushed through a thermoblock and into your portafilter? Answer:  with a pump.  What does the pump use for pressuring the coffee shot through?  Answer:  more water from the tank.
                              You assume, what I assume wrong! lol
                              You havent been reading my post properly. You are bing very rude and derogative now and not keeping to the subject. Please, step back in line and have some manners.

                              Comment


                              • #30
                                Re: Thermoblock versus Boiler

                                Originally posted by ShortBlack link=1118073813/15#18 date=1121165589
                                Monti, any thermoblock would be empty at the start of a shot.  Thats not the issue.  Regardless of the speed and volume, the start of the shot will be hotter than the finish because the water draws heat from the metal as it passes through.  The last 30 mls will have less heat to draw from the metal because it has been cooled by the first 30, and the metal wont have had the time to recover the right temperature.
                                Are you assuming that a whole lot of cold water hitting a thin little hot pipe?  Because I would suggest that rather it is small amounts of room temperature water hitting a thick and long thermoblock that is at the required temperature.  So, the heating element would not suffer from cooling down and the water could reach the required temperature rather fast.  If the mass of the hot pipe is large enough compared to the mass of the water traveling through it then there is no measurable or substancial loss of heat throughout the process, whether it is 30ml or 60ml going through it.  

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