# Pressure / Vacuum Analysis During Submersion

1. Aug 18, 2011

### navier1863

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. Aug 19, 2011

### edgepflow

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.

3. Sep 1, 2011

### navier1863

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?