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Old   July 14, 2009, 22:59
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muhammad irham mahfud
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hi,

i want to ask again about my case. my case is about pressure rise(unsteady) in multiphase closed system (vessel). my questions are:

1. because my case is closed system i just apply some heat flux in the domain.but in the specifying well-posed boundary conditions section said that my boundary condition is under specific problem because its just wall for heat flux.

2. thermal energy used for low speed but total energy may experience robustness problems due to the pressure. which is better for my case?

3. which is better to used eulerian or lagrangian multiphase model?

thanks,
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Old   July 15, 2009, 04:03
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Try to give a better description about your case
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Old   July 15, 2009, 04:39
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Quote:
Originally Posted by Rui View Post
Try to give a better description about your case
I have problem to getting convergence. i have vessel that hold liquid nitrogen. because heat leakage to the system the pressure will be rise, right? i want to know the pressure rise rate inside the vessel.thanks
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Old   July 15, 2009, 04:49
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1) better description means a full problem description and ccl if you want specific help.

2) Total energy. have a read in the manual but I attach a small extract which is relevant "For materials which have variable specific heats (e.g., set as a CEL expression or using an RGP table or Redlich Kwong equation of state) the solver includes the contribution in the enthalpy tables. This is inconsistent, because the variable is actually internal energy. For this reason, the thermal energy equation should not be used in this situation, particularly for subcooled liquids."

3)
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Old   July 15, 2009, 05:06
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To me, it seems you can do this by hand or in Excel.
Heat In -> Nitrogen Enthalpy Rise (E=m\cdot\Delta h) -> Obtain Pressure and Temperature from Thermodynamics Tables
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