Henk,
<How could I find acceptable values for the emissivity and absorptance of the soil surface. The soil is probably earth/grass but could perhaps be paved.>
Paved surfaces vs grass surfaces will have very different absorptivity and emissivity values. There are some great resources online - do a search on emissivity of materials. However, with that being said, we rarely use that approach when we studt horizontal GHX systems. The model does not take into account evapotranspiration and therefore the surface temperatures likely swing more in the model than they do in real life. I would suggest using the surface temperature mode corresponding to the long-term averages (Kusuda).
<With the input Zone convection coefficient, the comments state this is only used in zone surface mode 1 (energy balance), where is this set?>
Parameters in the model:
Insulated surface mode
Soil surface mode
<Also, what would be an appropriate value or how could one estimate this?>
It depends entirely on what is happening in your zone. Is the air stagnant, moving, etc. Refer to the Type 56 documentation for examples on convective heat transfer in zones.
<The incident short wave radiation (also used in surface mode 1) should be read from the weather file, does this need to go through a radiation processor as in other models? What output of that processor or weather file would be a good one to use?>
Be careful here. If the surface is within a zone then the incident short wave is likely from lighting although there could be solar radiation hitting the floor. If it's not within a zone then the incident radiation is solar and should come from the weather component (type 15). Most likely the total incident radiation on a horizontal surface.
<Sky temperature and incident solar radiation – same question>
The sky temperature input should be connected to the sky temperature output from the weather component,
Jeff
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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@tess-inc.com
On 02/14/2018 10:00 am, henk witte via TRNSYS-users wrote:
Dear fellow TRNSYS users,
I am currently building a model with the TESS type 997, horizontal heat exchanger, for the first time and have some questions about the parameterisation and inputs:
1) How could I find acceptable values for the emissivity and absorptance of the soil surface. The soil is probably earth/grass but could perhaps be paved.
2) With the input Zone convection coefficient, the comments state this is only used in zone surface mode 1 (energy balance), where is this set? Also, what would be an appropriate value or how could one estimate this?
3) Same question for Zone radiant temperature
4) The incident short wave radiation (also used in surface mode 1) should be read from the weather file, does this need to go through a radiation processor as in other models? What output of that processor or weather file would be a good one to use?
5) Sky temperature and incident solar radiation – same question
Any suggestions more then welcome!
Thanks,
Henk Witte
Groenholland Geo-energysystems
Valschermkade 26
1059CD Amsterdam
T: +31 (0)20 6159050
M: +31 (0)628176535
E: henk.witte@groenholland.nl
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