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Old   August 30, 2006, 06:08
Default temperature
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greg
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one more quastion

I have a problems with temperature of fluid. I have a container filled in half with water and above a water is h2o vapour. I have 3 udf`s. Mass transfer: from vapor to liquid and from liquid to vapor defined by Define_mass_transfer (hooked in phase interactions panel) and heat transfer defined in Define_source makro hooked in BC panel. Without mass transfer (but with heat transfer) everything is ok but when I turn on mass transfer a temperature above a fluid decrease during few iterations (time = 0,001s) to 1,0 deg K (from 333 deg K to 1K). Do you happen to know why? BC are 3 walls (one of them is with temperature 500 K and the rest are heat flux = 0). Upper wall is BC Outflow.

I wonder what is wrong because I use mass transfer for boiling (from logic point of view) so I provide (to vapour volume) a vapour (from boiling process) with temperature much higher that one above the liquid . I know that temperature in Fluent is limited to 1 and 5000 K. So 1K (like in my case) is lower limit. What to do??

My mass transfer udf is:

if(from_fhase == iliq) { Thread *gas=THREAD_SUB_THREAD(thread, to_phase); Thread *liq=THREAD_SUB_THREAD(thread, od_phase); if (C_T(cell, liq) >= T_SAT) { m_lg = (12 * (fabs(C_T(cell,liq)-T_SAT)))/2000; } if (C_T(cell, gas) < T_SAT) { m_lg = - (12* (fabs(C_T(cell,gas)-T_SAT)))/2000; } }

Any clues??

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