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Enthalpy source of Particle in DPM

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Old   April 18, 2013, 08:19
Default Enthalpy source of Particle in DPM
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Hi everybody,

I have a problem undestanding the enthalpy source terms in Fluent (14.5).

I'm working on my own DPM Particle Law for boiling of superheated droplets (all the energy for evaporation comes from within the droplet). I switched off all built-in particle laws to test my law, where I compute the new Mass, Diameter and Temperature of the droplet.

Now I still have to couple the Lagrangian droplet to the Euler-Phase through source terms. Mass source is not a problem, but the Energy source term is more difficult, since it consists of enthalpy through change of droplet temperature, enthalpy of the evaporated mass and its latent heat.Now I have the following problem: Usually in Fluent the Enthalpy source because of the evaporated mass at boiling temperature is calculated by
(T_boil-T_ref) * m_vaporated *c_p*strength.
Since the boiling temperature is smaller than the reference Temperature the source term is now negative! Why exactly do I need the substraction of T_ref here and how does Fluent handle the Enthalpy term? If I plot the "DPM Enthalpy Source" it is shown negative, but the temperature of the gas phase has risen, how is that possible?
In the manual DPM Enthalpy source is describes as follows: "The exchange is positive when the particles are a source of heat in the continuous phase. " which should be the case here. So what exactly is the sign-convention here since my negative source term rises the temperature?

Lots of questions, I would appreciate every help you can give me!
Thanks
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