airflow network
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nooshin abolhasani
Jul 21, 2013, 2:23:26 AM7/21/13
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Hi
I want to use airflow network in simulating my novel trombe wall.
There are some Questions:
1-If we want to use design builder to create Energyplus files, how we can define airflow network in DB?
2-Does EP consider a specific time of year in simulating airfows?
3-How we can define air flow network in EP?
4-Does EP have any visual output for the airflows?
Thanks a lot.
farhang.tahmasebi
Jul 22, 2013, 6:14:26 AM7/22/13
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Hi,
1) To start, you should go to building model options (F11) and change the natural ventilation from scheduled to calculated. Then, if you export an IDF model you can see the AFN objects there. But, as always keep in mind that when you use an interface like DesignBuilder, which defines tons of EnergyPlus objects just by one click, you should be familiar with these objects or at least understand the key inputs. Otherwise, in my opinion, it doesn't make any sense to use this feature. If you go further, we can discuss the key inputs and limitations of this method.
2) Not very clear. You run the model in a specific run period, so EP uses the weather data of that period (e.g. wind speed, and wind direction) and also the input wind pressure coefficients. You have also the venting availability schedules of windows to control their state of being open or closed.
3) Well, the answer is you should put some effort! Such a big question can not be answered here! You can read the I/O reference of EnergyPlus and do some reverse engineering with the DesignBuilder generated model.
4) No. Please don't expect something like visualizations of CFD outputs! AFN gives you one flow rate per each node (a window for example), and you can get it as a time-varying number during the run period. Of course the simulated air change rate is also available which is based on a lot of assumptions and inputs which you should be aware of.
Best,
--
M.Sc. Farhang Tahmasebi
PhD Candidate / Project Assistant
Department of Building Physics and Building Ecology
Vienna University of Technology
farhang....@tuwien.ac.at
1) To start, you should go to building model options (F11) and change the natural ventilation from scheduled to calculated. Then, if you export an IDF model you can see the AFN objects there. But, as always keep in mind that when you use an interface like DesignBuilder, which defines tons of EnergyPlus objects just by one click, you should be familiar with these objects or at least understand the key inputs. Otherwise, in my opinion, it doesn't make any sense to use this feature. If you go further, we can discuss the key inputs and limitations of this method.
2) Not very clear. You run the model in a specific run period, so EP uses the weather data of that period (e.g. wind speed, and wind direction) and also the input wind pressure coefficients. You have also the venting availability schedules of windows to control their state of being open or closed.
3) Well, the answer is you should put some effort! Such a big question can not be answered here! You can read the I/O reference of EnergyPlus and do some reverse engineering with the DesignBuilder generated model.
4) No. Please don't expect something like visualizations of CFD outputs! AFN gives you one flow rate per each node (a window for example), and you can get it as a time-varying number during the run period. Of course the simulated air change rate is also available which is based on a lot of assumptions and inputs which you should be aware of.
Best,
--
M.Sc. Farhang Tahmasebi
PhD Candidate / Project Assistant
Department of Building Physics and Building Ecology
Vienna University of Technology
farhang....@tuwien.ac.at
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