[TRNSYS-users] Type 703 example

[Jeff Thornton]

<I took a look at the example for TYPE 703 - Slab on grade and I saw
that the weather file is for Wisconsin-Madison. Parameter 10 in Type 703
- Day of minimum surface temperature is set to 36. But I imported the
weather file in Excel and checked if that is correct and I found that
the day of minimum ambient surface is 28. Is there a mistake in the
example or the way I checked isn't correct?> 

The day of the minimum
ambient temperature in the weather data file is likely 28 as you
suggest. But that data file is based on a real month's worth of data
from a given year that best matches the average month over a 30-year
period. Historically, I believe the day of minimum surface temperature
for Madison is near day 36. Use whatever value you're more comfortable
with. I would also point out that Type 703 is no longer part of the
standard package and has been replaced by newer and better models. You
should strongly consider upgrading to the new models. 

<I also need to
find the amplitude of surface temperature, which is the difference
between the maximum average monthly temperature and the minimum average
monthly temperature.> 

Not so fast. The amplitude actually has multiple
definitions unfortunately and the one that is used in TRNSYS for this
model is the peak deviation from the mean - not the crest to trough
value. For example the simple function for surface temperature in the
model is: 

T = X * Sin (Time + Y) + Z 

In this case, X is the
amplitude of the function and the crest is at Z + X and the trough is at
Z - X. 

<Do I have to average the hourly temperature in the imported
weather file in Excel for every month to find the two average
temperatures? Or is there an easier way? > 

That's the approach but
I've already done that for quite a few locations - so let me know if
you'd like the parameters for a particular city. I'd laos like to point
out that Type 15 calculates the monthly average temperatures and outputs
them. 

<The defined value in TYPE 703 is 13.32 and I have a question
about this value too. From the weather file I imported in Excel I found
that the average temperature in january for Wisconsin-Madison is
approximately -8 degC. I didnt't checked for the rest of the months, but
assuming that this temperature is the minimum average temperature and
that the maximum average temperature is a positive value (for example 20
degC in july), then the amplitude would be A=20-(-8)=28 degC. This value
is much greater than 13.32. Is there a mistake in the way I determined
the amplitude?> 

Yes - see above. You would need to divide by two in
your approach to get the amplitude for the model. 

Jeff 

---

Jeff
Thornton 

_President - TESS LLC_ 

_22 N. Carroll Street, Madison WI
USA 53703_ 

_Office: (608) 274-2577 Fax: (608) 278-1475_


_www.tess-inc.com_ 

_E-Mail: thornton at tess-inc.com_ 

 
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