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Dear Chiara, yes you are right. Use HTC = 0.01 kJ/k m² (not a smaller value!!!) for inside and outside to make the virtual window surface temperature approach
Tsky. Best _________________________________________________________________________________________________ Jakob Merk TRNSYS Software Team
Curiestraße 2 70563 Stuttgart Fax: +49 711 67976-11 Web: www.trnsys.de
Von: TRNSYS-users [mailto:trnsys-users-bounces@lists.onebuilding.org]
Im Auftrag von Chiara Colucci Hi Jakob, thank you for the reply. I think I will use the solution 1. About this I would like to know why you talk only inside HTC. Also
outside HTC has to be small? Best regard 2016-04-22 13:12 GMT+02:00 hotline <hotline@transsolar.com>: Dear
Chiara, A virtual surface isn’t the appropriate approach. Virtual surfaces should be used as adjacent surfaces between zones in SketchUp which
are merged into one zone with multiple airnodes. A virtual surface isn’t a heat transfer surface, it doesn’t exist in the thermal model.
Thus, the error message is correct. The volume of the canyon zone isn’t closed and therefore no view
factor matrix could be calculated. Modelling outdoor space isn’t a straightforward task. Solution 1 In order to generate a closed volume of the canyon and allow solar radiation to penetrate
into the zone you need a window. To do the shortwave solar correct you may use a so-called “no window”
which has a transparency of 100 %. However, this surface has a temperature and thereby influences the zone air temperature
by its inside convections heat transfer coefficient (HTC) and the longwave exchange by its temperature.
For reducing the influence on the air temperature you may define the inside HTC to
be small (like 0.01 kJ/k m²). For longwave radiation exchange the window temperature should be approximately the sky
temperature. However, you can’t fix a temperature of window. You have to try to calculate a surface
gain such that the Temperature is close and the model is still converging.
Solution 2 You use solution 1 for calculating the incident radiation (total and direct) on the
window and use this radiation as input to a model which doesn’t contain a “canyon zone”. For longwave radiation exchange
you have to estimate the “effective ground temperature”. All the best The Transsolar Software Team _________________________________________________________________________________________________ Jakob Merk TRNSYS Software Team
Curiestraße 2 70563 Stuttgart Fax:
+49 711 67976-11 Web: www.trnsys.de
Von: TRNSYS-users [mailto:trnsys-users-bounces@lists.onebuilding.org]
Im Auftrag von Chiara Colucci
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