Hello,
Recently, i found this interesting paper:
Rasmus K. Ursem, Thiemo Krink, and Bogdan Filipic
A Numerical Simulator for a Crop-Producing Greenhouse
Regards
Christian
SAP Senior Application-Developer
-----Original Message-----
From: knut.erik.enerstvedt@niva.no
[mailto:knut.erik.enerstvedt@niva.no]
Sent: Tuesday, January 20, 2009 10:21 AM
To: rguechchati@gmail.com; d_azelarabe@yahoo.fr
Cc: trnsys-users@cae.wisc.edu
Subject: Re: [TRNSYS-users] Greenhouse
Rahma Guechchati and Azelarabe Dkaki,
I have previously asked questions about TRNSYS and
greenhouses to the
forum. Below you can find the answers I got.
Kind regards,
Knut Erik Enerstvedt
Dear all,
I wish to use Type 56 to model a greenhouse, and would
like to know if
there is an appropriate building template available
from somewhere.
Best regards,
Knut Erik Enerstvedt
Knut-Erik,
Not that I am aware of - when we have had to model
greenhouses, they have
just been normal Type56 zones with a lot of windows. I
have even had pretty
good luck getting Window5 to come up with window
properties for some of the
glazing materials that are used in greenhouses but not
in buildings
(celular plastic panels, etc.). There are some
problems with treating the
greenhouse as a typical Type56 zone in that Type56
does not account for
beam radiation that passes right through a zone as is
the case when you get
a large fraction of windows. I asked a similar
question on this forum some
time ago and got some useful help.... the thread is
attached below:
>From Pierre HOLLMULLER
I confirm that our monitoring data (18 month in 5
minute step, also
available in 1 hour step) would be available for
testing of such a
greenhouse model. The data concerns 3 identical
agricultural greenhouses,
of which 2 were equipped with daily heat storage
systems (water tank and
air/soil heat exchanger).
For the standard greenhouse (without storage), the
data concerns :
- solar radiation
- ambient temperature and humidity
- internal temperature and humidity at 1 and 2 m
height
- temperature of internal shading device
- soil temperature at 40 and 70 cm depth
- auxiliary heating
- humidification system
- opening of windows and activation of shading device
A detailed report can be found on:
http://www.unige.ch/cuepe/html/biblio/detail.php?id=20
It is in French, but going quickly through the figures
will give you an
idea of what was done and what is available (see in
particular annex 1)
>From Ian BEAUSOLEIL-MORRISON
I suggest you look at some of the work published by
Jan Pieters et al. of
Ghent University (Belgium). They presented an
interesting paper at the
System Simulation in Buildings conference last
December, but I am not sure
whether there are proceedings available yet.
>From Michaël KUMMERT:
You may find some information in a paper that was
recently presented at the
"Systems Simulation in Buildings" conference:
E. Mashonjowa, J. G. Pieters, J. R. Milford1, F.
Ronsse, S. Denys, R.
Lemeur - THE USE OF A TRNSYS BASED DYNAMIC GREENHOUSE
CLIMATE MODEL TO
SIMULATE THE MICROCLIMATE IN A TYPICAL ZIMBABWEAN
GREENHOUSE in proc. of
the 7th International Conference on System Simulation
in Buildings
(SSB), Liège, Belgium, December 11-13.
The authors use the so-called "Gembloux Dynamic
Greenhouse Climate Model
(GDGCM)" that was originally written for TRNSYS 13 and
was adapted and
validated in TRNSYS 16. Another reference is:
Pieters J. G. and Deltour J. M. 1997. Performances of
greenhouses with the
presence of condensation on cladding. J. Agric. Engng.
Research. vol. 68:
p. 125-137.
Kind regards,
David
> 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
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
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!
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
Knut Erik,
I am not 100% sure that I follow your question about
slopes - do you have
a cross section of the greenhouse that you can send me
so I can see?
Usually if you have an upward slope and a downward
slope, the two surfaces
are defined separately with the same slope but with
opposite azimuth
angles.
I left all the geosurf values set to 0 in my case.
My thinking was that
if there were no plants, then it would be more
appropriate to set geosurf
to 1 for the floor and 0 for everything else. However,
the plants are going
to absorb most of the radiation and turn it into
growth so there won't be
much direct radiation hitting the floor and allowing
it to do so would
mislead the model.
For the capacitance, I think I set the lower zone to
10 times the default
value and the upper zone to 5 times the default value
(I didn't have any
particular justification for my choice though)...
Kind regards,
david
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17.01.2009 19:03
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----- Message from "Rahma GUECHCHATI"
<rguechchati@gmail.com> on Sat, 17
Jan 2009 10:51:26 +0000 -----
To: trnsys-users@cae.wisc.edu
Subject: [TRNSYS-users] Fwd: Greenhouse
Hello;
I want to make a simulation of a greenhouse by using
software TRNSYS.
Can i use type 56 to carry out the energy assessment
of a greenhouse and
which are the necessary parameters to take into
account.
Thank you,
Kind regards,
Rahma
----- Message from Azelarabe Dkaki
<d_azelarabe@yahoo.fr> on Mon, 19 Jan
2009 10:07:58 +0000 (GMT) -----
To: TRNSYS-users@cae.wisc.edu
Subject: [TRNSYS-users] (no subject)
Hello TRNSYS-users,
currently I work on the greenhouse by using the
software of simulation
TRNSYS, can you give me some refer which can help me.
It's the first time that I work with this software.
Best regards.
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