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How could the volume flow rate at the Supply node be lower than the flow rate at the outdoor air inlet?

C:\fakepath\hrv inlet vs supply.PNG

Outputs show 1. Outdoor air fraction = 1 2. Economiser bypass = 0 3. Inlet flow rate > Supply flow rate

I assume that EnergyPlus does a mass balance in the HVAC air loop. Is that correct? Are there any components in an airloop that can leak? C:\fakepath\hrv inlet vs supply.PNG

How What could the volume explain why I am seeing Volume flow rate (Standard Density) at the Supply node be lower than the flow rate at the outdoor air inlet? I assume that the volume flow rate downstream of the outdoor air Inlet could only be the same (or higher if mixed with return air) ?

C:\fakepath\hrv inlet vs supply.PNG

Outputs show 1. show

1. Outdoor air fraction = 1 2. Economiser 1
2. Economiser/HX bypass = 0 3. 0
3. Inlet flow rate > Supply flow rate

I assume that EnergyPlus does a mass balance in the HVAC air loop. Is that correct? Are there any components in an airloop that can leak?

What could explain why I am seeing Volume flow rate (Standard Density) at the Supply node lower than the flow rate at the outdoor air inlet? I assume that the volume flow rate downstream of the outdoor air Inlet could only be the same (or higher if mixed with return air) ?

Outputs show

1. Outdoor air fraction = 1
2. Economiser/HX bypass = 0
3. Inlet flow rate > Supply flow rate

I assume that EnergyPlus does a mass balance in the HVAC air loop. Is that correct? Are there any components in an airloop that can leak?

The results below are mostly ok for the second day. Other AHUs are showing much worse agreement.