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High current in a supercooled wire?

  1. Apr 12, 2016 #1
    I'm trying to understand heat-transferring process and the maximum amount of current and coolant required to apply and maintain(for a short-duration) high current in a certain conductor, before I start considering an experiment, I'd rather have my work correct in-terms of the calculations and predictions of what might happen.

    The conductor is a copper plate, the dimensions: 250mm H x 5mm W x 10mm T
    Weight: 111.58 grams

    Can this conductor sustain 50kA in a duration of 100ms without fusing/melting?

    Since it's a plate, I used this online calculator for a quicker computation of the resistance and confirmed it with my own work they are approximately the same, the resistance at room temperature is: 0.0000843 Ohms.

    The idea here is to have the conductor initially cooled to -196°C using liquid nitrogen, using the same calculator above I changed the temperature to -196°C, and now R = 0.0000117 Ohms

    Using Ohm's law I'm assuming that the applied voltage(##V##) would be: ##0.0000117\Omega \times 50kA## = ##0.585V## The power is ≈ ##30kW##

    Now when working out the heat transfer and the rate of transfer I lose myself, it's like all the things I studied in Physics 101 and Chem. 101 faded away... here are some questions I couldn't figure out aside from the initial one:

    1) How long would it take to cool the plate from RT(20 - 25°C) to (-196°C) to apply the 50kA?
    2) How much(volume) liquid nitrogen would I need to sustain this process for 100ms?
    3) How long would it take to cool the wire(or transfer all the dissipated power) for a re-run(somewhat relates to Q1)?
    4) Would the induced magnetic field have any ramifications? I assume a large spike if disconnected quickly due to the induced EMF.

    The reason I considered liquid nitrogen is to reduce the resistance greatly, and cool the system rapidly, however, I think water would be a good substitute? Or even air cooling? Or possibly both or all?
    I'm pretty sure due to the rapid boiling of liquid nitrogen I'd require a lot of it.
  2. jcsd
  3. Apr 12, 2016 #2


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    This experiment is far too dangerous for anyone with limited technical knowledge to contemplate doing . If it had to be carried out for some real purpose then stringent safety precautions would be required .
  4. Apr 12, 2016 #3
    Have you considered the skin effect?

    To calculate this you will need to know your waveform and its bandwidth.

    The heat of fusion of nitrogen is 5.56 kJ/mol. So to dissipate 3000 joules (30,000 kW over 0.1 sec), a bit over 4 mols of vaporized N2. This gets into the Leidenfrost area I think.
    Last edited by a moderator: Apr 12, 2016
  5. Apr 12, 2016 #4


    Staff: Mentor

    Closed pending moderation.

    Edit: we will go ahead and leave this closed due to safety policy.
    Last edited: Apr 13, 2016
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