# HVAC modeling problem

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 February 26, 2009, 15:40 HVAC modeling problem #1 David Guest   Posts: n/a I followed the tutorial 17 for modeling of an HVAC system in a room, and made some changes to the geometry of the room. Now when I run the solver I get the error # 001100279 has occurred in the subroutine ErrAction - Floating point exception: Overflow. The solver will make it through the first iteration, but always gets hung up on the second iteration at the point when it is calculating turbulence kinetic energy and eddy dissipation. I have tried bumping my allocated memory up and I have also changed the eddy dissipation length from the .25m value given in tutorial 17 to automatic, and automatic with value. I still get the same error during the same iteration.

 February 26, 2009, 16:17 Re: HVAC modeling problem #2 David Guest   Posts: n/a Are there other ways to dumb down the model? Maybe my mesh is too complex?

 February 26, 2009, 17:27 Re: HVAC modeling problem #3 Glenn Horrocks Guest   Posts: n/a Hi, Floating point exception means the linear solver has diverged big-time. You need to numerically stabilise the simulation. You can do that by a combination of: improving mesh quality, smaller timesteps, double precision, simpler turbulence model, upwinding for advection (just to start things off), time stepping based on local time scale, or a few other things (but they are the main ones). Glenn Horrocks

 February 26, 2009, 18:16 Re: HVAC modeling problem #4 David Guest   Posts: n/a Thanks alot. From your help and others on this board I was able to make this simulation work. What I did was practically double the mesh size, cut the time step in half, and I chose the SST turbulence model. I think I will try increasing these attributes in small increments until I get the result I want. This board is very informative. I have learned more CFD analysis in the past week, than my entire college career.

April 21, 2011, 09:00
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William Shaw
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Quote:
 Originally Posted by David ;92097 I followed the tutorial 17 for modeling of an HVAC system in a room, and made some changes to the geometry of the room. Now when I run the solver I get the error # 001100279 has occurred in the subroutine ErrAction - Floating point exception: Overflow. The solver will make it through the first iteration, but always gets hung up on the second iteration at the point when it is calculating turbulence kinetic energy and eddy dissipation. I have tried bumping my allocated memory up and I have also changed the eddy dissipation length from the .25m value given in tutorial 17 to automatic, and automatic with value. I still get the same error during the same iteration.
I am quite new to ICEM and CFX. I want to build a geometry just like tutorial 17 and mesh it. But I really don,t know how to make a window on a side of wall or an outlet on the ceiling. Plus I feel really confused of the meah.Could you show me how to make it? Thanks!

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