DESIGN BUILDER CFD BOUNDARY

asked 2020-06-18 07:37:23 -0500

HJOJOA gravatar image

updated 2020-06-18 11:45:14 -0500

For a CFD simulation in designbuilder, a simple office box with one four ways supply and one extract:

  • Surface temperatures were imported from EP simulation results
  • The only one supply condition is 1400 CFM and 53F supply temp (the same from EP simulation result)
  • Only one extract
  • In the energy simulation from EP envelope, people, equipments were defined
  • The only conditions evaluated in CFD are envelope condition but use the same air flow results with the same supply result from simulation (also a 15% safety factor was applied.

Like i have mentioned before, the wall, roof and floor temperaures were taken from SIMULATION result, also the supply airflow and supply temperature were from design day calculation.

The mesh is ok and the simulation converge, but when see the results the indoor temperatures are 3 o four degrees higher than expected, checking results i see than supply temperature is higher the supply input (53 F).

The question are general :

  • Why the simulation result shows that supply temperature is higher than the supply setted in the diffuser boudary?

  • If the only load condition evaluated in CFD is the envelope and it is assumed that the air flow and supply temperature condition used in said simulation is sufficient and oversized by 15% for (envelope + internal loads), why the Indoor temperature is higher than expected?

  • Shouldn't the declared supply condition in the 4-way diffuser boundary condition remain constant in 53F?

  • Is there some configuration OR SETTING TO ASSURE THE SUPPLY CONDITION IS CONSTANT?

  • Is the atmospheric pressure used in the CFD the same from project used in EP simulation?

I do not expect to have an answer on the model because i didnt share, what I hope are setting recommendations to review or to apply in the system.

Thanks

Thanks for your support

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