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Pressure / Vacuum Analysis During Submersion

  1. Aug 18, 2011 #1
    I have a product that we perform submersion testing on to determine susceptibility to water intrusion. The product is heated to 120C and then placed in an ice bath. I have measured the pressure / vacuum during testing and have determined that the pressure can rise to 5 psi while heating and drop to -10 psi while submerged.

    The ideal gas law aligns with the 5 psi while at 120C but when dunked, the calculations state that the pressure should be around -2 psi. I am trying to determine how to calculate this result. Any advice?
     
  2. jcsd
  3. Aug 19, 2011 #2
    Double check your numbers. I get close to your measured value with ideal gas assumption.

    If you want to show your math, we maybe can find the problem.
     
  4. Sep 1, 2011 #3
    During testing of the product, I am seeing pressure swings of 12.5 psi. Initially I assumed that volume remained the same (which is not correct but I will get to that). The following are calculations:
    - P1 * V1 = n R T1
    - Final Pressure = (Delta T) * Initial Pressure

    If I use the test data that indicates the pressure can change by 12.5 psi, the volume would need to change by approximately 41.8%. There is something else occurring that I am not accounting for. Any thoughts??? Is there anything related to humidity that might be affecting this test?
     
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