Principal variable in energy equation is total enthalpy or total internal energy?
Hi, there
When I use ‘Total energy’ as the heat transfer model, may I know if the principal variable in energy equation is total enthalpy or total internal energy? From the CFX theory guide as shown in the following link: https://www.sharcnet.ca/Software/Ans....html#BGBCHDHC in the energy equation, d(rho ht)/dt is subtracted by dP/dt, which equals to d(rho et)/dt, where et is the total internal energy. Does this mean the principal variable in energy equation is total internal energy? Otherwise, why do we need to subtract dP/dt? PS, I found the majority solvers are all internal energy base, not enthalpy based. Thanks! |
The total energy equation has 3 variables to represent energy:
1 - Internal energy in the transient term 2 - Total enthalpy in the advection term 3 - Temperature in the conduction term You have a choice to make, the ANSYS CFX Solver decided to solve for total enthalpy; therefore, it is convenient to write the equation in terms of the unknown. As long as the equation represents the total energy conservation in the frame of choice, any variable is OK. |
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For steady state, the dP/dt term would be 0 at convergence; therefore, there is no need to discretize it.
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