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simulation load by using airflow network and ideal load air system

asked 2019-09-18 03:00:43 -0500

xianxian's avatar

updated 2019-09-18 03:54:19 -0500

I want to simulate the load in different areas of the high-large space (high-speed rail station) under natural ventilation (opening door ventilation).

Due to the wind infiltration at the entrance to the high space, the wind speed at the entrance is within 0-3 m3/s.

In order to simulate the wind speed of each area, I divided the vertical and horizontal directions of the high space into multi-zone and established an inter window(simple opening and horizontal opening) between the zone and the zone.

Can the Airflow network simulate the load of each space relatively accurately?can I ignore the role of air momentum?

image description

But at the moment my simulation does not seem to be successful, the load is very large in the outer ring (especially at the air inlet), but the load inside is very small, and the gap between the outer ring and the outer ring is very large.

The figure below is the data of the load of zones. image description

Another problem is that the temperature in the room is uniform at the same time without air conditioning. Why is the load gap of each zone very large and the indoor temperature (without ideal air system) is very uniform? The figure below is the data of the temperature of zones at the same time(13:00 design day).

image description

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answered 2019-09-18 13:29:51 -0500

I should probably just close this as a duplicate, but since you've added additional content I won't. Presumably you have connected the zones together with elements that are low resistance, but it would be helpful to include that information. I can't really answer your first question (Can the Airflow network simulate the load of each space relatively accurately?) without more details. But I'll go with "no, it probably is not doing that". The answer to your second question (can I ignore the role of air momentum?) is easy, though. You don't have any choice because momentum is not conserved by the equations that AirflowNetwork solves, so it's getting ignored.

  • AirflowNetwork solves a system of (nonlinear) equations based on conservation of mass. Momentum is not conserved.
  • The connections between nodes and the resistance to flow associated with those connections determines where air can flow (or not). It is not like CFD where, given a good mesh, the equations will figure it out for you.

I would not expect meaningful results from this simulation. EnergyPlus is not the correct tool.

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Thank you very much for your answer again. I did ask a similar question. I tried to use Room air + CFD according to your previous suggestions. However, this method does not get the load of different areas, I have to give up. I will try to solve this problem using other methods. Thank you again for your reply.

xianxian's avatar xianxian  ( 2019-09-18 22:25:21 -0500 )edit

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Asked: 2019-09-18 03:00:43 -0500

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Last updated: Sep 18 '19