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Re: [EnergyPlus_Support] Supply and return airflow rates do not match in AFN




Timestep=1 --> hourly
Timestep=60 --> minutewise simulation
I meant to try decrease the timestep of the simulation as conditions may be changing too dramatically from step to step if your interval is too large, I.e. set Timestep=60.
This is the second time I've seen this error mentioned, but I can't recall the solution. Perhaps, another solution would be to ramp up the airflows of your mechanical systems, or alternatively switch on the AFN only when everything is up and running.

Mit freundlichen GrüÃ?en- Sent from my iPhone (excuse the brevity)
i. A.
Jean Marais
b.i.g. bechtold
Tel.   +49 30 6706662-23
On 05.05.2014, at 19:35, Solomon Yin <<mailto:solomonyp@xxxxxxxxxxx>solomonyp@xxxxxxxxxxx> wrote:

>  
> Jean
> I just tried with timestep=1, still not working. 
> It seems like something wrong with the objects in AirflowNetwork:Distribution. When I run the simulation without modelling AFN:distribution, it gave me reasonable results on infiltration.
> Solomon
> 
> To: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: <mailto:jeannieboef@xxxxxxxxx><mailto:jeannieboef@xxxxxxxxx>jeannieboef@xxxxxxxxx
> Date: Mon, 5 May 2014 19:15:02 +0200
> Subject: Re: [EnergyPlus_Support] Supply and return airflow rates do not match in AFN
> 
>  
> Did you try to reduce the timestep?
> 
> 
> 2014-05-05 1:00 GMT+02:00 <<mailto:solomonyp@xxxxxxxxxxx><mailto:solomonyp@xxxxxxxxxxx>solomonyp@xxxxxxxxxxx>:
>>  
>> Dear E+ users:
>> 
>> 
>> I am trying to simulate the energy loss through an air distribution system by using the Airflow Network in E+. My building is a single story, rectangle residential house with unconditioned attic where ducts are located. The space heating and cooling are provided by a central warm-air furnace with gas heating and electric cooling. The severe error resulting from running AFN model is listed as 
>> 
>> 
>>  ** Severe  ** AirflowNetwork: The airflow direction is opposite to the intended direction (from node 1 to node 2) in AirflowNetwork:Distribution:Linkage = SUPPLY DUCT LINK 1
>>    **   ~~~   **  During Warmup, Environment=COOLING DESIGN DAY, at Simulation time=07/21 00:00 - 00:15
>>    **   ~~~   ** The sum of the airflows entering the zone is greater than the airflows leaving the zone (e.g., wind and stack effect).
>>    **   ~~~   ** Please check wind speed or reduce values of "Window/Door Opening Factor, or Crack Factor" defined in AirflowNetwork:MultiZone:Surface objects.
>> 
>> 
>> However, the MultiZone Airflow works fine when AFN Control was set as MultizoneWithoutDistribution.
>> 
>> 
>> I tried to fix this severe error by adjusting the Wind Speed, Crack Factor, Airflow Convergence Tolerance, Air Mass Flow Coefficient, and Maximum Iterations, but none of them works. 
>> 
>> 
>> Dose anyone have a clue on how to fix this issue?
>> 
>> 
>> Thanks
>> 
>> 
>> Solomon
>> 
> 
> 
> 



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