[TRNSYS-users] More questions about Type 56 and greenhouses

[knut.erik.enerstvedt@niva.no]

David,

I wonder if I can ask you some more questions about your TRNSYS greenhouse
model?

I wish to model a greenhouse with sloped roof and more than one top. In
Type 56, will adding one wall tilted in the first direction and a second
wall tilted in the other direction have the same effect as adding several
walls in both directions, as long as the surface area matches?

I usually set geosurf to zero for all surfaces to keep things simple. Do
you think this is acceptable for a greenhouse?

How did you define the horizontal shade/thermal screen to reflect changes
in radiation to the lower zone? A window with an internal shading factor?

What do you think the thernal capacitance should be in a greenhouse (upper
and lower zones)?

Did you ever have the model verified in some way?


Thanks again for your help. I really appreciate it.


Kind regards,
Knut Erik



                                                                           
             David Bradley                                                 
             <bradley@tess-inc                                             
             .com>                                                      To 
                                       knut.erik.enerstvedt@niva.no        
             08.10.2008 18:28                                           cc 
                                       trnsys-users@engr.wisc.edu          
                                                                   Subject 
                                       Re: [TRNSYS-users] Type 56 building 
                                       template for greenhouses            
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Knut Erik
> Did your greenhouse consist of just a single Type 56 zone, or several?
> Maybe two zones: One for the main compartment and one for the top
> compartment?
>
our model had two zones - one below and one above. In our greenhouse,
there was a controlled horizontal shade that got pulled across just
above the plants if they got too hot. We used CONTAM coupled with TRNSYS
to determine the air exchange between the two (CONTAM is quite similar
to COMIS)
> How did you define the walls? I have tried to define very thin walls with
> huge windows, but have problems with the timebase because the walls are
so
> lightweight. Do you think I can use a massless wall?
>
I think you could probably just ignore the walls completely unless they
make a significant thermal bridge. If they do, then I would just treat
them as massless.
> Also, did you use one huge window for each wall or many smaller windows?
>
I treated it as one big window because that is how the greenhouse was
set up in my case. If the actual greenhouse is a lot of windows, then
thermally, there isn't much difference as long as you take care to set
the framing factor correctly in the window Typemanager.

Kind regards,
 David








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