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Thread: Mollier charts

  1. #1
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    Mollier charts



    Hi guys,

    I am currently trying to supply my customers with more than just a signed a work sheet saying their system has been maintained(as this is all the company I work for provide). My boss seems reluctant to put the effort in so I plan on taking matters into my own hands.

    only thing is that I've only ever plotted a mollier chart when I done my 2079.

    any idea where I can buy charts for various gases? And also where I would be looking to get my temperature readings off an air con vrv on heating and cooling modes? Might seem like a stupid question but i just want to make sure I get this correct first time so my company enforces them.

    Thanks in advance guys.



  2. #2
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    Re: Mollier charts

    You can download them from the web, just type the refrigerant you need.

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    Re: Mollier charts

    Quote Originally Posted by RIK-MAY View Post
    Hi guys,

    I am currently trying to supply my customers with more than just a signed a work sheet saying their system has been maintained(as this is all the company I work for provide). My boss seems reluctant to put the effort in so I plan on taking matters into my own hands.

    only thing is that I've only ever plotted a mollier chart when I done my 2079.

    any idea where I can buy charts for various gases? And also where I would be looking to get my temperature readings off an air con vrv on heating and cooling modes? Might seem like a stupid question but i just want to make sure I get this correct first time so my company enforces them.

    Thanks in advance guys.
    No need to buy use

    http://www.ipu.dk/English/IPU-Manufa.../CoolPack.aspx

    It is free and very good.

    If you want to spend money then buy a set of Testo gauges or other
    data logging equipment and run the machine for 24 hours with the data
    logger recording all the required information.

    You can then download to your PC and print as a document.

    Regards

    Rob

    .
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  4. #4
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    Re: Mollier charts

    That sorts out the charts so thanks for that.

    with regards to the plotting of the charts can you tell me the exact place to get the readings before I plot the chart?

    and will it be the same places during heating as opposed to cooling? Obviously just switching the readings as the 4 way valve redirects the flow.

  5. #5
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    Re: Mollier charts

    .

    You have to get the figures.

    You need suction pressures / temps.
    You need discharge pressure / temps.
    You need to measure the subcooling on the liquid line.
    You need to measure the superheat on the suction line.

    You then input all this detail and the software will then draw
    you a cycle based on your readings.

    Remember the cycle is only good for the moment you plot it,
    if something changes then the cycle will change.

    The system will show you the heat output as well as the Refrigeration Effect,
    but you need to be able to interpret all the figures.

    You will need to learn to use the Ph chart (Mollier chart) because it
    can do very simple calculations or it can be used to very complicated calcs.

    Regards

    Rob

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  6. #6
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    Re: Mollier charts

    Superb rob.

    thanks a lot.

  7. #7
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    Re: Mollier charts

    Rob,

    ive familiarised myself with the software and it seems very helpful.

    only thing is that I'm not 100% sure on where to enter all my info. Il list all the required fields it's asking for and hopefully you can help.

    evap temp
    superheat
    dp evaporator
    dp suction line
    dp discharge line
    isentropic efficiency
    condensing temp
    subcooling
    dp condenser
    dp liquid line

    can you tell me exactly what these mean. Some are obvious but the "dp" part especially has me scratching my head.

    Sorry to grill you on all this but if I don't ask I won't know.

  8. #8
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    Re: Mollier charts

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  9. #9
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    Re: Mollier charts

    Quote Originally Posted by RIK-MAY View Post
    Rob,

    ive familiarised myself with the software and it seems very helpful.

    only thing is that I'm not 100% sure on where to enter all my info. Il list all the required fields it's asking for and hopefully you can help.

    evap temp (found by using gauges to measure suction pressure / temp. Evap temp)
    superheat (Found by measuring the suction pipe temp and comparing to evap, gauge temp)
    dp evaporator (pressure drop over evap. Ignore for now that is more complex)
    dp suction line (pressure drop over suction pipe. Ignore for now)
    dp discharge line (Pressure drop over discharge pipe. Ignore)
    isentropic efficiency (leave as set. This is the compressors efficiency and more complex)
    condensing temp (found from gauges. Discharge pressure / temp)
    subcooling (found from measuring liquid pipe (before expnsion valve) and comparing to gauge temp)
    dp condenser (pressure drop over condenser. Ignore for now)
    dp liquid line (pressure drop over liquid pipe. Ignore for now)

    can you tell me exactly what these mean. Some are obvious but the "dp" part especially has me scratching my head.

    Sorry to grill you on all this but if I don't ask I won't know.

    See what I've put in the brackets.

    Rob

    .
    Last edited by Rob White; 01-04-2013 at 02:12 AM.
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  10. #10
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    Re: Mollier charts

    That's better. I only remember posting 4 points on a chart. Makes much more sense now.

    thanks a lot for your help.

  11. #11
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    Re: Mollier charts

    Seems what you are wanting to do is a bit of an overkill, you will confuse the heck out of client who will in turn will disregard and bin it. You would be better off to get a temp data logger and supply a graph of temps that client can understand.

  12. #12
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    Re: Mollier charts

    Ignoring DP over evaporator !!?? You can have more than 1 bar over the coil.
    A real life chart consists at least of 7 pressures and corresponding temperatures.
    Drawing a theoretical chart of a real-life machine will not give you correct results.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  13. #13
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    Re: Mollier charts

    I want to compare the performance of several compressors for a project, would using ph diagrams be a suitable method, can you see any problem with this? (first time i have come across them) Also, given the data available on http://www.novakool.com/support/bd35...essor_data.pdf , the BD35F sheet, would it be possible to derive all the other variables required to Input into the CoolPack software to give a correct P-H diagram?
    Thank you for any help

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