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Thread: E-61 group head - how does it get heated?

  1. #1
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    E-61 group head - how does it get heated?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight

    Howdy Coffee Gurus,

    Ive been looking at machines with the E-61 group head, as patented by Vibiemme. I understand that the group head stays hot due to the hot water circulating internally through it, however I dont understand what causes that circulation in the first place. Is there a pump that is constantly running, and circulating water from the boiler, or is it through a process of convection?

    Can anyone comment?

    Im a thermoblock person wanting to upgrade to a pointy end machine.

    Lawrance :)

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    Mal Dimal's Avatar
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    Re: E-61 group head - how does it get heated?

    Gday tv8,

    Basically, its just convection flow circulation and is not just restricted to E-61 Group designs, lots of Group designs use this principle to maintain operating temperature. I think there are plenty of explanations about this to be found by searching the Net but heres one from Home Barista that Ive read before.... Scroll down to about half-way down the page and youll see a simplified diagram coupled with an explanation of how it works,

    Cheers,
    Mal.

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    Re: E-61 group head - how does it get heated?

    Yep, correct me if I am wrong, but it is from the water flashing to steam in the heat exchanger building up pressure, pushing it up into the group to heat it, then as it cools, it turns back to water and is replaced by more superheated water from the HX.

    I think that was an extremely simplified explanation of Mals "convection flow circulation" for people not so familiar with fluid thermodynamics (if that is the correct descriptor) :P

    John.

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    Re: E-61 group head - how does it get heated?

    From the Home Barista link in Mals post: (if you cant be bothered reading the whole thing) I think this explains it all ;)

    (Source: http://www.home-barista.com/forums/the-e61-group-truth-and-lies-t724.html)


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    Mal Dimal's Avatar
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    Re: E-61 group head - how does it get heated?

    Quote Originally Posted by itsme5k link=1187750612/0#2 date=1187756121
    think that was an extremely simplified explanation of Mals "convection flow circulation" for people not so familiar with fluid thermodynamics (if that is the correct descriptor) :P
    Not sure what youre getting at here John :-?? Are you suggesting that I should have gone into a more complete scientific description of the full thermodynamic profile of this design? If someone needs that kind of information, they are probably already of a scientific/engineering bent and know of more appropriate locations to source this sort of info.... Cant see that this site requires that level of detail unless it is specifically requested and my impression was that a simplified explanation was asked for in this case.... I could be wrong?

    Cheers,
    Mal.

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    Re: E-61 group head - how does it get heated?

    More along the lines of giving my understanding of it, then reading through the link you provided, saw the picture and thought that explained everything perfectly.

    The reason I mentioned it flashing from the HX to build up pressure, well that is just adding the information where the heat and water for the thermo siphoning are coming from (I am new to all this too, and previously thought it was directly from the boiler) and thought this clarification may be of some help (it took me a while to work it out playing with the machine).

    I am only trying to deepen my knowledge of this subject as well as it is an interesting one (especially for someone who is curious about anything technical and also has an E-61 machine...)

    Not implying a more scientific answer was needed, I just thought "the water flashing to steam in the heat exchanger building up pressure, pushing it up into the group to heat it, then as it cools, it turns back to water and is replaced by more superheated water from the HX" would have been the simplest explanation.
    By "that was an extremely simplified explanation of.." I only meant it in the way that to most of the non technically minded members of my family, answering this question by saying " its just convection flow circulation" would probably just be returned by a blank stare.

    I honestly dont think either way of explaining was wrong. Sorry if I offended in any way :P

    YT
    John

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    Re: E-61 group head - how does it get heated?


    OK, so let me understand this in laymans terms - basically this means I have to wait about 20 minutes after the machine is turned on from cold so that the boiler has time to heat up, then the convection currents have time to warm up the head before I can make one decent cup?

    Im trying to translate the technical back to what it means for me in a practical sense.....

    So to answer my own question, how does it get heated, the answer is - slowly? :P

    Are there any machines out there with a pump that actively pushes the hot water through the group head instead of relying on convection?




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    Re: E-61 group head - how does it get heated?

    Wont running the pump a few times after the boiler is up to pressure do this?
    I do that in the morning when I have limited time, I have the PF locked in so that gets heated by the water too.

    I havnt timed but I would say about 10-15 min would be acceptable.

    Still, gotta love the EM6910 for taking no more than 5 before everything is up to temp :P

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    Re: E-61 group head - how does it get heated?

    Quote Originally Posted by itsme5k link=1187750612/0#5 date=1187760025
    I honestly dont think either way of explaining was wrong. Sorry if I offended in any way :P
    No offence taken John, just seemed as though you thought my response was over-simplified, and that wasnt my intention either by the way as I thought that most people understand the basics of convection flows going back to probably grade 10 science, or even earlier?

    Anyway, for what its worth..... I dont believe that the water in the HX/Thermosyphon circuit flashes to steam as such, since an equilibrium is established from the onset of turning power on to the machine. If there is indeed an "air-space" within the heat exchanger then there will be a gradual pressure build-up in this circuit that will prevent "flash-boiling" from occurring until such time as the circuit is opened (flushing the group) and the pressure is reduced thereby stimulating the "steam dance" that is often reported when group flushing is first performed after significant delays of inactivity. The Thermosyphon water circulation is due only to the physics of Fluid Convection Flows once equilibrium is established, Im pretty certain of that.

    Quote Originally Posted by tempestv8 link=1187750612/0#6 date=1187760873
    OK, so let me understand this in laymans terms - basically this means I have to wait about 20 minutes after the machine is turned on from cold so that the boiler has time to heat up, then the convection currents have time to warm up the head before I can make one decent cup?

    So to answer my own question, how does it get heated, the answer is - slowly? :P
    In a nutshell, youve got it.... [smiley=laugh.gif]

    Quote Originally Posted by tempestv8 link=1187750612/0#6 date=1187760873
    Are there any machines out there with a pump that actively pushes the hot water through the group head instead of relying on convection?
    I havent heard of one doing it this way but that doesnt mean it hasnt been tried or is in fact being used by one or more manufacturers at this moment. With decent sized boilers and HX units, convection flows offer the use of a free source of energy that is otherwise being untapped, and this is why it is such a great thing to use, its available, it uses little additional energy, its simple and when designed properly, is quite efficient.... So it doesnt make a lot of sense to add complexity to a design when something so simple is very effective.

    Of course, some manufacturers use independent heating elements to heat the Groups and maintain them at optimum brew temperature but I dont know whether these companies maintain the existence of the Thermosyphon circuit and utilise the additional heating elements as an adjunct to this or do away with the Thermosyphon circuit altogether. One of our more scientifically qualified members "Sparky" has delved into the workings of many espresso machine designs so he may be able to throw some light on this particular aspect of Group Temperature Maintenance. Hope this has helped a bit..... :)

    All the best,
    Mal.



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