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How can I get the measure "air speed (m/s)" to be seen in results viewer?

asked 2018-02-17 19:23:21 -0500

Elissa's avatar

updated 2018-05-21 15:12:15 -0500

I'm using OS 1.10.0 + SU Pro 2016 and EP 8.4.0

I'm calculating PMV and PPD for my model and I've already selected the necessary measures for calculating it, but there's one I don't know where to find or how to add in "Output Variables", which is AIR SPEED/AIR VELOCITY (or indoor air speed) of each space of the residential model I'm working in.

The only one according to air speed I found was "Zone Outdoor Air Wind Speed" which is not an interior measure.

Could you help me find/add it please?

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answered 2018-02-19 13:31:54 -0500

StefanG's avatar

The air speed input for thermal comfort calcs is not something you'll find as an energyplus output. This is the local air speed that is traveling across occupants. Energyplus can't really calculate this. In an ideal world you would have something like a CFD tool to understand the airflow in the space, but this is usually not practical.

Typically you will have to make an assumption here. ASHRAE publishes upper limits to what they consider acceptable air speeds for indoor spaces. There are a few studies which show interior air speeds when using ceiling fans, which I believe can show up to 0.6 m/s of air speed on average when in use.

This thread provides a bit of guidance, suggesting 0.1-0.15 m/s for typical forced air systems.

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answered 2018-02-18 00:23:54 -0500

Avi's avatar

updated 2018-02-18 09:35:02 -0500

What you refer to as Air Speed is referred by E+ as Flow Rate. Look up in the .rdd file which you will find under the run subfolder of your project folder.

If you search that file for flow rate you will find current and standard density flow rates of different liquids and gases in the model. Hopefully one of them would be the one you look for.

You can use the Input Output Reference to check about them.

Edit: Once you find the name of the Variable you need in the .rdd file (and this is the list of all available variables to your version of E+ and to your specific model) you will need to select them for Output.

In order to select a variable to be output you may use the add_output_variable measure. You could use the link or within OS Measures tab click Find Measures on BCL in the lower right corner. Then Reporting > QAQC. When you run the measure you will have to enter the Variable Name, Reporting Frequency and the Key Name.

You should run the measure once so use the apply measure now from the Components&Measures menu. After you run the measure and the simulation examine the .err file to make sure it was added correctly.

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There isn´t any value. Let me explain better, maybe I was not very clear... When I open the results viewer, I can access the results I need for: - mean radiant temperature; - air temperature; - operative temperature - relative humidity And the only one is missing and I can´t find in the "Output Variables" list to turn on is: AIR VELOCITY/AIR WIND SPEED/FLOW RATE (m/s) except the Outdoor air wind speed, which I don't need for applying the PMV method.

Is there any way of adding it to the output variables list? Or is there anything I should do to be able to access these values?

Elissa's avatar Elissa  ( 2018-02-18 06:50:34 -0500 )edit

@Elissa See my edit to my answer.

Avi's avatar Avi  ( 2018-02-18 09:35:29 -0500 )edit

I think you'll find air speed is a Schedule. Try extracting the variables Schedule Values

TomB's avatar TomB  ( 2018-02-18 20:33:27 -0500 )edit

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Asked: 2018-02-17 19:23:21 -0500

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Last updated: Feb 19 '18