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# Two way flow in simple and detailed opening

Query: what is the difference between simple and detailed opening. which option should I consider? what is the basis?

how two way flow phenomenon is different in Simple and Detailed opening?

AFN Linkage Node 1 to 2 mass flow rate and AFN Linkage Node 2 to 1 mass flow rate

At times, Why both of these are on (or) giving positive values? (Across windows) what do you mean by that? in that case if I want to determine the net flow into the space Do I need to sum these both flow rates to determine the flow of air into the space.

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First try changing the reporting frequency in the Output:Variable objects to Detailed so you see that AFN Linkage Node 1 to 2 and Node 2 to 1 have opposite signs. I assume you are using Timestep or Hourly which gives averages over time when the system time step (HVAC) is less than the zone time step. Each should give flow into one zone.

( 2018-10-31 15:59:24 -0500 )edit

@rraustad perfect, it worked..But they do not have opposite signs rather AFN Linkage Node 1 to 2 mass flow rate is coming as postive and AFN Linkage Node 2 to 1 mass flow rate is coming as zero.......and this makes really sensible...meaning flow is happening from 1 to 2 (inside to outside).......at some instances, AFN Linkage Node 1 to 2 mass flow rate is coming as zero and AFN Linkage Node 2 to 1 mass flow rate is coming as positive which means flow is happening from 2 to 1 (outside to inside)....

( 2018-10-31 16:18:39 -0500 )edit

@rraustad yes, I am using timestep and hourly as reporting frequencies

( 2018-10-31 16:20:10 -0500 )edit

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The difference between the simple opening and detailed opening is the complexity of the inputs required for the model. The Input Output Reference describes these differences. For both these objects it is possible to have both positive and negative flows depending on the neutral height location on the surface. See the documentation for more information. And as described, the detailed reporting frequency is best for diagnosing results when questions arise since longer reporting frequencies will average the results.

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