About thermal calculation

[Li Yin]

Hi everyone, 

I'm a beginner in thermal simulation. I tried to do the thermal calculation of a fixed window to practice. Seems like my result is different from the one showed in the thermal report from another person. Does anyone have any clue about the difference? I was thinking about maybe they got the result by doing the simulation in half of the drawing model (sill or right jamb is showing both sides of two glasses). Or should I do the simulation by drawing only half of the model of the sill or jamb which includes two sides of defferent windows? Does anyone know about the correct way to do the simulation on glazing system which has shared jambs or sills? I put the results in attached files. Might be helpful to understand. Many thanks to any helpful suggestions here. 

Kind regards, 

Li 

[Collin Robinson]

Hi Li,

I fiddled with the file a bit, checking boundary conditions etc. I ended up with a similar result as you, see attached, until I realized #1. A couple thoughts:

1. The U-factor tag lengths in the report are much less than that in the file you shared. Frame tag is 147mm vs 39mm in report. I think they were looking at just the part of the frame whereas you tagged the whole aluminum part as frame. When I just tagged the lower part up to the 1st EPDM seal, it seems to be similar. I don't know enough to say whether this is legit practice or not, to split it this way. I have not done it this way, usually I look at the whole aluminum piece and call it a vertical meeting rail. That works with how I know how to use WINDOW. 

2. The face of that part of the frame looks thicker in the report than in your file. That may explain why they are getting a slightly higher frame U than I did. 

I hope this helps, was an interesting mystery to me. See attached BC and Tag diagram and revised file. 

Collin

[Li Yin]

Hi Collin, 

Thanks for your reply. Sorry for the late reply. I got back to the office and tried the file you sent to me this morning. Actually the result is really close to the one in the report. I'm still not sure about the correct way to do the simulation. I also checked the manual book's meeting rail part. The manual book says the whole frame and two glazing systems will be simulated, and the program averages the values for both to derive one Edge U-factor. But the manual book doesn't mention how to deal with the edge length or frame length. The Figure 8-1. Meeting rail cross section shows that the two sightlines determine the Edge-of-glass delimeter for the Boundary Conditions. Is it the problem that I did not link materials to the glazing system cavity? Or I made some mistakes in setting the Boundary Conditions? I'm still confused by the report and related problems. Thank you for your help anyway. At least I know that the whole frame simulation should not be a wrong way to do the simulation. 

Kind regards, 

Li Yin

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