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Is it possible to get the window surface temperature in EnergyPlus?

asked 2017-04-19 03:53:14 -0500

Joe Huang gravatar image

updated 2017-04-20 13:39:13 -0500

I've been asked to identify the extreme climate conditions that would stress thermally windows and cause cracking. In general terms, one would think it would be rapid temperature rise combined with high solar gain and low wind speeds, but I'm stumped in figuring out how to weigh these difference conditions to derive the extreme condition.

It then occurred to me, why not use EnergyPlus to track the window surface temperature which should be the combined effect of the environment causing thermal stress in windows. So, I took the 5zone building model and simplified it as much as possible, but I can't find anywhere in the documentation a variable for the temperature of the glass. Does anyone know whether it's possible to extract the surface temperature, or is it something that can be calculated from other variables?

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answered 2017-04-19 11:09:15 -0500

Both inside and outside surface temperatures are available as output variables. You request the time series (any aggregation level) using the output:variable object. In the latest release, 8.7, you can specify output variable names using regular expressions.

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At the risk of getting a "check the user manual" rebuke, how do I reference the four windows for which I want the surface temperatures? In DOE-2, one would call out the object name, i.e., NORTHWNDW, etc., but I've never tried doing that in IDF. Or do I have to use regular expressions, and if so, is that explained in the documentation? I'm still using EPlus 8.0 .

Joe Huang gravatar imageJoe Huang ( 2017-04-19 19:58:23 -0500 )edit

You don't have to use regex. You can just request four output variables, one for each window of interest.

Output:variable, NORTHWINDOW, Outside Surface Temperature, hourly;
Output:variable, WESTWINDOW, Outside Surface Temperature, hourly;

And so on.

__AmirRoth__ gravatar image__AmirRoth__ ( 2017-04-20 08:41:58 -0500 )edit

I tried that but it didn't work. The *.err file says

*** Simulation Error Summary ***

* Warning * The following Report Variables were requested but not generated

* ~~~ * because IDF did not contain these elements or misspelled variable name -- check .rdd file

*** Key=NORTHWNDW, VarName=OUTSIDE SURFACE TEMPERATURE, Frequency=Hourly etc.

But I've checked to make sure that the KEYs are correctly spelled (NORTHWNDW, etc.), don't know about the VarName, though. BTW, I'm running EPlus Version 7.0, not 8.0.

Joe Huang gravatar imageJoe Huang ( 2017-04-21 21:43:28 -0500 )edit

As the error message says ... the recommended way to do this is to open the .rdd file, grep for the surface names you want, and then copy the lines corresponding to the variables/frequencies you want into your IDF file.

__AmirRoth__ gravatar image__AmirRoth__ ( 2017-04-22 11:07:11 -0500 )edit

Where does one get the *.rdd file? I've checked my E+ output files, and there is no file with the *.rdd extension. Does it have to be requested? Also, does it exist in E+ 7.0 ?

Joe Huang gravatar imageJoe Huang ( 2017-04-27 01:16:28 -0500 )edit

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Asked: 2017-04-19 03:53:14 -0500

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Last updated: Apr 19