FDS simulation with abnormal temperature

[Alex Wang]

Dear sirs,

       In the FDS simulation, I used 3-D heat conduction model, and in the first 4,700 seconds, the temperature of the combustible ('A') surface was normal, but in the end of the simulation(4700s-4900s), the surface temperature was abnormal, with a minimum temperature as low as -209.6 ° C. Why this abnormal temperature occurs? How can I fix it. Attach file is the code.

[dr_jfloyd]

 &MATL ID= 'A' DENSITY = 15 CONDUCTIVITY = 500 SPECIFIC_HEAT = 0.2 /

This is a very extreme material in terms of its properties. The very low density and very high thermal conductivity does not seen like a real material. This might be causing some numerical issues. Setting CHECK_HT might help. Also HT3D is a beta feature,   You may want to also try the latest test release of FDS which has some updates and bug fixes to HT3D. 

[Alex Wang]

Thank you for your kindly response! I will try it...