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  • Normal flow converter

    Hi friends
    I'm Hamidreza and working in glass industry.
    we have plc that calculate normal flow of furnace burners.
    in plc settings:
    air pressure ref:0.943 bar
    Air temp ref:20 c
    gas pressure ref:1.013
    gas temp ref:0 c
    Are these correct???
    Anybody know why are these set???
    I think pressure and temp ref should be same.
    #mass_flow_converter
    #sorg
    Last edited by Hamidreza68; 11-20-2018, 11:11 PM.

  • #2
    Originally posted by Hamidreza68 View Post
    Hi friends
    I'm Hamidreza and working in glass industry.
    we have plc that calculate normal flow of furnace burners.
    in plc settings:
    air pressure ref:0.943 bar
    Air temp ref:20 c
    gas pressure ref:1.013
    gas temp ref:0 c
    Are these correct???
    Anybody know why are these set???
    I think pressure and temp ref should be same.
    #mass_flow_converter
    #sorg
    I can't be sure. The volume of a gas depends on its temperature and pressure. It is common to calculate the volume of a gas at "normal" or "standard" conditions instead of actual conditions. It is confusing because different industries use different values for normal or standard. For your gas (whatever it is), "normal" in chemistry is almost always 101.325 kPa (about 1.013 bar) and 0 C. Does the equipment have sensors for actual temperature and pressure in the gas line? I suspect it is simply converting between "actual" and "normal" gas volume. That would be very common.

    For the compressed air industry, 20C or 25 C is often used, also at a pressure of 101.325 kPa for "free air.". Is your plant at relatively high altitude about sea level? The air conditions might simply be "typical" for your plant. Otherwise, I have no explanation for the air reference pressure.

    Probably not the complete answer, but I hope it helps a little. If you have experienced co-workers, they may known exactly why.

    Comment


    • #3
      Originally posted by JohnS View Post

      I can't be sure. The volume of a gas depends on its temperature and pressure. It is common to calculate the volume of a gas at "normal" or "standard" conditions instead of actual conditions. It is confusing because different industries use different values for normal or standard. For your gas (whatever it is), "normal" in chemistry is almost always 101.325 kPa (about 1.013 bar) and 0 C. Does the equipment have sensors for actual temperature and pressure in the gas line? I suspect it is simply converting between "actual" and "normal" gas volume. That would be very common.

      For the compressed air industry, 20C or 25 C is often used, also at a pressure of 101.325 kPa for "free air.". Is your plant at relatively high altitude about sea level? The air conditions might simply be "typical" for your plant. Otherwise, I have no explanation for the air reference pressure.

      Probably not the complete answer, but I hope it helps a little. If you have experienced co-workers, they may known exactly why.
      Thanks johns
      I have another problem
      I calculate normal flow by hand and there are difference between my calculation and plc calculation.
      we know that the formula is p1v1/t1=p2v2/t2
      plc calculate gauge pressure and reference pressure in this formula.
      but absolute pressure must be calculated in that formula.
      am I right???

      Comment


      • #4
        Originally posted by Hamidreza68 View Post

        Thanks johns
        I have another problem
        I calculate normal flow by hand and there are difference between my calculation and plc calculation.
        we know that the formula is p1v1/t1=p2v2/t2
        plc calculate gauge pressure and reference pressure in this formula.
        but absolute pressure must be calculated in that formula.
        am I right???
        Yes, both pressure and temperature must be absolute in any application of Ideal Gas Law. Add (local) atmospheric pressure to gauge pressure, and 273.15 to temperature to convert degrees Celsius to kelvins. For pressure, "standard" atmospheric pressure may be a reasonable approximation but local, actual is better.

        Comment

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