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Thread: Superheat horn

  1. #1
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    Superheat horn



    A system running on a type 2 refrigerant such as R134a exhibits a superheat horn on the pressure enthalpy diagram but a system running on a type 3 refrigerant has not superheat horn because the shape of the saturated vapour curve is such that when you start compression with a saturated vapour the exist of the compression lies in the two phase region.

    My question is what effect does in the real world?

    Is it just that with type 3 refrigerants if there is no suction superheat then there is no discharge superheat?
    And with type 2 refrigerants that even with no suction superheat that there will be discharge superheat?


    Jon


    Mostly found in Oxfordshire, UK :)

  2. #2
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    Re: Superheat horn

    any pics of your horn?

    al
    Mostly found in the southern part of this green and pleasant land.

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    Re: Superheat horn

    Easy there Al , don't go spilling the bean's so to speak.

    Cheers

    Stu
    Tool's ? check ! Condom's ? check !
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  4. #4
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    Re: Superheat horn

    With no superheat you have liquid entering the compressor
    I'm back on the Pale

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    Re: Superheat horn

    Not sure what you mean about your horn, (means something different in my terms)
    But i think to answer your question.
    look at P-H diagram, you will see some lines marked "s"
    So at your comp inlet point SST, follow the "s" line until it insects your discharge pressure (SCT)
    Now at this point see how the "s" line intersects the Temperature curves. This will give the you the theoretical discharge temp and remove the SCT from this number to give actual amount of discharge superheat. But you then to include efficiency, which then alters the figure.

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    Re: Superheat horn

    Was watching a vid on youtube on vapour compression cycle by Prof. M Ramgopal, have a look around 33 minutes into the vid.

    http://www.youtube.com/watch?v=x9yirfC8niI

    The horn thingy is shown on page 5 of this link,

    http://lcs.syr.edu/faculty/khalifa/M...ationPrint.pdf

    Most of it was beyond my understanding but the idea that you could compress a refrigerant and it not be superheated made me wonder if i understood correctly.

    Jon
    Last edited by monkey spanners; 31-10-2011 at 10:17 PM.
    Mostly found in Oxfordshire, UK :)

  7. #7
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    Re: Superheat horn

    Quote Originally Posted by mad fridgie View Post
    Not sure what you mean about your horn, (means something different in my terms)
    But i think to answer your question.
    look at P-H diagram, you will see some lines marked "s"
    So at your comp inlet point SST, follow the "s" line until it insects your discharge pressure (SCT)
    Now at this point see how the "s" line intersects the Temperature curves. This will give the you the theoretical discharge temp and remove the SCT from this number to give actual amount of discharge superheat. But you then to include efficiency, which then alters the figure.

    On the example they showed, due to the shape of the temperature curve the discharge temp was inside the curve so no superheat with type 3 refrigerant.
    See vid link in my other reply.
    Jon
    Mostly found in Oxfordshire, UK :)

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    Re: Superheat horn

    Now I like type 2 refrigerants and I like type 3 refrigerants..But which one is better?

    There's only one way to find out.............................

  9. #9
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    Re: Superheat horn

    Not a refrigerant that I have used. But does follow the rules as indicated. The practical issues relate to the type of plant, Does liquid actually form during the compression process, or does the vapour remain super-cooled.Does the varying efficiency factors elevate the vapour temp actually above the 2 phase zone
    Very Interesting!!!!!!!!????????

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