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Heat balance in radiation simulation

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Old   December 6, 2005, 09:49
Default Heat balance in radiation simulation
  #1
Rivera
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Hi,I have some questions when using immersol radiation model. Below is the q1 file. If it reaches the heat balance, the enthalpy out from the outlet should be less than that from the inlet. But the .res file showed the reversed result. why? And, I also want some advice on setting the relaxiation factors, especially for factors of T3 and TEM1.

TALK=T;RUN( 1, 1)

************************************************** **********

Q1 created by VDI menu, Version 3.5, Date 20/10/03 CPVNAM=VDI;SPPNAM=Core ************************************************** ********** IRUNN = 1 ;LIBREF = 0 ************************************************** ********** Group 1. Run Title TEXT(No title has been set for this run. ) ************************************************** ********** Group 2. Transience STEADY = T ************************************************** ********** Groups 3, 4, 5 Grid Information

* Overall number of cells, RSET(M,NX,NY,NZ,tolerance) RSET(M,20,1,35) ************************************************** ********** Group 6. Body-Fitted coordinates ************************************************** ********** Group 7. Variables: STOREd,SOLVEd,NAMEd ONEPHS = T

* Non-default variable names NAME(144) =WDIS ; NAME(145) =WGAP NAME(146) =T3 ; NAME(147) =SCAT NAME(148) =EMIS ; NAME(149) =EPKE NAME(150) =TEM1

* Solved variables list SOLVE(P1 ,U1 ,W1 ,T3 ,TEM1)

* Stored variables list STORE(EPKE,EMIS,SCAT,WGAP,WDIS)

* Additional solver options SOLUTN(P1 ,Y,Y,Y,N,N,Y) SOLUTN(TEM1,Y,Y,Y,N,N,Y) TURMOD(KEMODL)

************************************************** ********** Group 8. Terms & Devices TERMS (T3 ,N,N,Y,N,Y,N) ************************************************** ********** Group 9. Properties PRESS0 = 1.000000E+05 SETPRPS(1, 0) DISWAL DVO1DT = 3.410000E-03 PRNDTL(T3 ) = -2.580000E-02 ;PRNDTL(TEM1) = 1.000000E+00 PRT (EP ) = 1.314000E+00 ************************************************** ********** Group 10.Inter-Phase Transfer Processes ************************************************** ********** Group 11.Initialise Var/Porosity Fields FIINIT(WDIS) = 1.000000E-01 ;FIINIT(SCAT) = 0.000000E+00 FIINIT(EMIS) = 0.000000E+00

No PATCHes used for this Group

INIADD = F ************************************************** ********** Group 12. Convection and diffusion adjustments

No PATCHes used for this Group ************************************************** ********** Group 13. Boundary & Special Sources

No PATCHes used for this Group

EGWF = T ************************************************** ********** Group 14. Downstream Pressure For PARAB ************************************************** ********** Group 15. Terminate Sweeps LSWEEP = 600 RESFAC = 1.000000E-03 ************************************************** ********** Group 16. Terminate Iterations ************************************************** ********** Group 17. Relaxation RELAX(P1 ,LINRLX, 2.000000E-01) RELAX(U1 ,FALSDT, 2.000000E-01) RELAX(W1 ,FALSDT, 2.000000E-01) RELAX(KE ,LINRLX, 5.000000E-01) RELAX(EP ,LINRLX, 5.000000E-01) RELAX(T3 ,FALSDT, 3.000000E+01) RELAX(TEM1,FALSDT, 3.000000E+01) KELIN = 3 ************************************************** ********** Group 18. Limits VARMAX(U1 ) = 1.000000E+06 ;VARMIN(U1 ) =-1.000000E+06 VARMAX(W1 ) = 1.000000E+06 ;VARMIN(W1 ) =-1.000000E+06 ************************************************** ********** Group 19. EARTH Calls To GROUND Station USEGRD = T ;USEGRX = T GENK = T ASAP = T PARSOL = T ************************************************** ********** Group 20. Preliminary Printout ECHO = T ************************************************** ********** Group 21. Print-out of Variables OUTPUT(WDIS,Y,N,N,N,N,N) ************************************************** ********** Group 22. Monitor Print-Out IXMON = 10 ;IYMON = 1 ;IZMON = 7 NPRMON = 100000 NPRMNT = 1 TSTSWP = -1 ************************************************** ********** Group 23.Field Print-Out & Plot Control NPRINT = 100000 ISWPRF = 1 ;ISWPRL = 100000

No PATCHes used for this Group ************************************************** ********** Group 24. Dumps For Restarts

GVIEW(P,0.000000E+00,-1.000000E+00,0.000000E+00) GVIEW(UP,0.000000E+00,0.000000E+00,1.000000E+00)

> DOM, SIZE, 1.000000E+00, 1.000000E+00, 1.000000E+00
: DOM, MONIT, 4.750000E-01, 5.000000E-01, 1.812500E-01
: DOM, SCALE, 1.000000E+00, 1.000000E+00, 1.000000E+00
: DOM, SNAPSIZE, 1.000000E-02

> OBJ, NAME, B3
: OBJ, POSITION, 0.000000E+00, 0.000000E+00, 0.000000E+00
: OBJ, SIZE, 5.000000E-02, 1.000000E+00, 2.500000E-02
: OBJ, CLIPART, cubet
: OBJ, ROTATION24, 1
: OBJ, TYPE, PRESSURE_RELIEF
: OBJ, PRES_RELIEF, 1.000000E+03, 0.000000E+00

> OBJ, NAME, INLET
: OBJ, POSITION, 0.000000E+00, 0.000000E+00, 4.000000E-01
: OBJ, SIZE, 0.000000E+00, 1.000000E+00, 2.000000E-01
: OBJ, CLIPART, cube3t
: OBJ, ROTATION24, 1
: OBJ, TYPE, INLET
: OBJ, PRESSURE, 0.000000E+00
: OBJ, VELOCITY, 1.000000E+00, 0.000000E+00, 0.000000E+00
: OBJ, TEMPERATURE, 2.730000E+02
: OBJ, TURB-INTENS, 5.000000E+00

> OBJ, NAME, OUTLET
: OBJ, POSITION, 1.000000E+00, 0.000000E+00, 4.000000E-01
: OBJ, SIZE, 0.000000E+00, 1.000000E+00, 2.000000E-01
: OBJ, CLIPART, cube12t
: OBJ, ROTATION24, 1
: OBJ, TYPE, OUTLET
: OBJ, PRESSURE, 0.000000E+00
: OBJ, TEMPERATURE, SAME
: OBJ, COEFFICIENT, 1.000000E+03
: OBJ, TURBULENCE, SAME , SAME

> OBJ, NAME, B6
: OBJ, POSITION, 0.000000E+00, 0.000000E+00, 0.000000E+00
: OBJ, SIZE, 1.000000E+00, 1.000000E+00, 5.000000E-02
: OBJ, CLIPART, cube4
: OBJ, ROTATION24, 1
: OBJ, TYPE, BLOCKAGE
: OBJ, MATERIAL, 100
: OBJ, HEAT_FLUX, 0.000000E+00,-6.000000E+03
: OBJ, EMISSIVITY, 1.000000E+00

> OBJ, NAME, B7
: OBJ, POSITION, 0.000000E+00, 0.000000E+00, 9.500000E-01
: OBJ, SIZE, 1.000000E+00, 1.000000E+00, 5.000000E-02
: OBJ, CLIPART, cube4
: OBJ, ROTATION24, 1
: OBJ, TYPE, BLOCKAGE
: OBJ, MATERIAL, 100
: OBJ, HEAT_FLUX, 0.000000E+00, 5.000000E+03
: OBJ, EMISSIVITY, 1.000000E+00 STOP

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Old   January 6, 2006, 17:51
Default Re: Heat balance in radiation simulation
  #2
mick
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I copied and pasted your q1, removing the comments. Did some small grid adjustment to sqaush the grid nearer the wall blockages and changed the relaxation settings and ran. I obtained heat balance for TEM1 and a -1000 Watt deficit for T3.

In my opinion from experimenting with this case.......

The fluid medium is non-particpating and hence the radiation only drives temperature in the wall blockages. This temperature then can only be transferred back into the fluid through convective and diffusive flux at the walls. Since your ficticiouis fluid has low thermal capacitance the heat (loss) released back to the fluid through conv+diff is small and negligable and hence we struggle to get a heat balance and convergence.

I believe you are are correct and in a full steady state solution the enthalpy leaving the outlet should be less then that entering through the inlet so that there is a balance when the nett source for TEM1 and T3 is added together.

If you make the fluid say water the case should run much better and convergence should be easier to achieve.

Infact I think the nett source for TEM1 should be + 1000 and the nett source for T3 -1000.

I have always been advised to set Tem1 and T3 relaxations to the same value, and use linrlx I usually start with -0.5 for both and decrease the value as necessary.

I hope this helps. I just think that your case is difficult because its difficult to get the heat from the walls back into the fluid from convection and diffusion. It seems to me that its a bit like trying to strain a brick through a sieve and this makes it very difficult to converge.

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