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Modelling vents in Energyplus Airflow network

asked 2015-06-22 04:22:59 -0500

updated 2018-08-25 18:16:10 -0500

Hello, I want to model a window vent in energyplus by using a crack in an airflow network. Is there a way to limit the mass flow rate through a crack to a constant (maximum) value from the moment that a certain pressure difference over the crack is reached? I can't figure out how to do this.

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answered 2019-01-30 02:22:00 -0500

This problem is tackled in the Ventilation Controls Virtual Test Bed. A paper containing more info can be found on: free download before March 21, 2019.

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answered 2015-06-25 07:57:53 -0500

Lixing Gu gravatar image

The Airflow Network is unable to do what you want. The model calculates flow rate based on pressure difference across a crack only. I will add an enhancement item for future development.

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Hello, thank you. I already altered the source code for the linear calculation option so that a deltaP maximum can be defined in an extra input field in the crack component. If deltaP > deltaPmax --> deltaP=deltaPmax.I don't get any errors for the moment, but I still have to do some tests.

BBel gravatar image BBel  ( 2015-06-26 09:17:55 -0500 )edit

Thanks for letting me know your modification. When you reset deltaP=deltaPmax, you should be able to get the flow rate you want. Could you let me know what deltaP is reported? How much difference between deltaP and deltaPmax?

Lixing Gu gravatar image Lixing Gu  ( 2015-06-26 10:08:12 -0500 )edit

Hello. After some testing the altered code didn't converge to a solution. I thought that this could be the result of the slope suddenly (instead of gradually) becoming zero at deltaPmax. I took a look at the self-regulating Vent model in contam (based on Axley, AIVC TN54 pp41-44) and I have tried to implement this (Q=Qref.(1.0-exp(-DP/DPref)) in the C++ code. The code compiles, but there is still no convergence. I have send you the altered source code files by mail. Could you have a look at them please. Thank you.

BBel gravatar image BBel  ( 2015-07-03 03:35:59 -0500 )edit

Hello Mr. Gu. I recently restarted my attempt for creating self-regulating vents in E+. This time I was successful. I have sent you the changed source code files and I have posted a ticket on the E+ helpdesk #10836

BBel gravatar image BBel  ( 2015-10-07 03:33:09 -0500 )edit

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Asked: 2015-06-22 04:22:59 -0500

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Last updated: Jan 30 '19