[TRNSYS-users] Modelling a greenhouse using Type 56

[knut.erik.enerstvedt@niva.no]

David,

Thanks again for a thorough answer.

I have some more questions related to the same topic:

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 (upward slope)
and a second wall tilted in the other direction (downward slope) 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?

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


Thanks again and kind regards,
Knut Erik



                                                                           
             David Bradley                                                 
             <bradley@tess-inc                                             
             .com>                                                      To 
                                       knut.erik.enerstvedt@niva.no        
             29.10.2008 18:08                                           cc 
                                                                           
                                                                   Subject 
                                       Re: [TRNSYS-users] Modelling a      
                                       thermal screen/horizontal shade in  
                                       a      Type 56 greenhouse           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Knut Erik,
 I think your approach is good. The one thing that you have to keep in
mind is that with CONTAM (or COMIS / TRNFlow), the flow through a
horizontal opening is uni-directional because it is driven by a pressure
difference and a temperature difference. Those flow paths do not have an
ability to show an updraft in the middle of a zone and a downdraft at
the perimeter. This can lead to a non-convergent solution in CONTAM.
Sometimes you have to artificially restrict the effective size of the
horizontal opening to prevent too large a volume of air from going from
one zone to the other. I have talked to the CONTAM developers about the
problem and how best to try and solve it but we have never come up with
a very good verdict.
Kind regards,
 David

PS: hopefully, Transsolar will answer the question about the NTYPE...
those confuse me terribly and I don't want to tell you something that is
incorrect!


knut.erik.enerstvedt@niva.no wrote:
> Dear TRNSYS users,
>
> I am trying to model a greenhouse with a thermal screen using Type 56.
The
> greenhouse consists of two zones, one above and one below, with the
screen
> as a horizontal shade between the zones. My plan to model the screen is
to
> define an ADJACENT window between the upper and lower zone, choose a
window
> with no glazing (non-existant or open) and have an internal shading
device
> controlled by an input variable. I will also use CONTAM to calculate the
> air exchange between the two zones.
>
> Can anyone tell me if this approach seems reasonable or not?
>
> I also need to know the amount of radiation being transmitted through all
> windows of the lower zone (including the virtual screen window) to
> determine the radiation level just above the plants. Does anyone know the
> proper NType for this?
>
> All help is higly appreciated.
>
>
> Kind regards
> Knut Erik Enerstvedt
>
>
>
>
>
>
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NIVAs hovedkontor har flyttet til nye lokaler i CIENS - Forskningssenter
for miljø og samfunn; Gaustadalléen 21, 0349 Oslo. Meld deg på vårt
nyhetsbrev på www.niva.no