[TRNSYS-users] Variable solar absorption coefficient and long waive emissivity in TRNSYS

[hotline]

Dear Marco,

unfortunately, the solar absorption as well as the long wave emissivity coefficients of opaque surfaces can't be changed during the simulation currently.

If you want to vary the coefficients on the outside face of an external wall, you may use the following "workarounds":

  *   Instead of modifying the solar absorptance you can modify the absorbed solar radiation by varying the external shading factor for a wall.
(Note: the external shading factor influences the incident solar radiation not the longwave radiation exchange)
  *   Instead of modifying the outside emissivity of an external wall you set the outside emissivity to 0 and calculate the energy gain/loss to longwave radiation exchange with the environment "manually" by equations and link the value as "surface gain outside" to the surface.
The equations for the longwave radiation exchange outside are given in 05-MultizoneBuilding.pdf  Eq. 5.4.1-13 and Eq. 5.4.1-14

The draw back of the "workaround" is that you have to do this for each surface. Doing this by a "construction type" is of course much more comfortable.
Well, it doesn't seems hard to implement this as a "new feature".  Are you interested in varying the values on the inside face of the outside face of a wall?

Best regards,

Marion



Transsolar Software Team
hotline at transsolar.com

Transsolar
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Von: TRNSYS-users <trnsys-users-bounces at lists.onebuilding.org> Im Auftrag von Marco Noro via TRNSYS-users
Gesendet: Dienstag, 26. Juli 2022 14:14
An: trnsys-users at lists.onebuilding.org
Cc: Marco Noro <marco.noro at unipd.it>
Betreff: [TRNSYS-users] Variable solar absorption coefficient and long waive emissivity in TRNSYS

Dear TRNSYS-users mailing list,

I would like to kindly ask you how is possible to implement the variable absorption characteristic of walls in TRNSYS. When using TRNSYS and TRBUILD, fixed solar absorption and long waive emissivity are allowed to be set when defining a wall layer. How do you managed the necessity to give variable (with the surface temperature) values of such parameters?

Thank you in advance for your cooperation.

Best regards

Marco Noro

***************************************************
Marco Noro, PhD
Associate Professor

Department of Management and Engineering - University of Padova
Stradella San Nicola, 3  -  36100  Vicenza (VI)  -  Italy
Ph.  +390444 998704
Email   marco.noro at unipd.it<mailto:marco.noro at unipd.it>
PEC     marco.noro at pec.it<mailto:marco.noro at pec.it>
Skype   nereo3
Web     Marco Noro (google.com)<https://sites.google.com/site/marconoro03>


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