You do not need to specify Zone:Infiltration
object to use
Zone:ThermalChimney object. If you use Zone:Infiltration object, the
total infiltration airflow through the zone is the sum of the airflow
from Zone:Infiltration and the enhanced natural ventilation from
Zone:Thermal Chimney.
As I mentioned below, I don't have anough experience with AirflowNetwork,
but I am pretty sure that the discharge airflow through the upper opening
in the thermal chimney model does NOT automatically interact with upper
window specified AirflowNetWork object unless you manually connect them.
The discharge air "temperature" through the chimney upper opening
is only
used "internally" inside the thermal chimney algorithm. So it does
not
directly affect other heat balances in EPlus. Only the enhanced natural
ventilation rate affects the heat balances.
Kwang
> A last observation I made explains why the airflownetwork method is not
> working properly:
> Actually, the suction effect of the chimney is linked, even defined by
the
> discharge air outlet description (as it is the case in the algorithm for
> ThermalChimney object). In fact in the airflownetwork calculation, this
> discharge opening does not behave as a one way flow opening. Because it
> uses LVO theoretical background most of the air mass exchange occurs at
> the opening and a very little fraction is actually sucked from the lower
> part. From there, all the massflow equilibrium at the different openings
> or cracks of this system cannot represent the situation.
>
> Do you see a solution in this? I am using Eplus V3 which has only LVO
> models capabilities. I know in V4 there is a new large horizontal
opening
> model that might be able not to have this behavior right?
>
> Best Regards
> Aymeric
>
> --- In EnergyPlus_Support@ yahoogroups. com,
"aymericnovel"
> <aymericnovel@ ...> wrote:
>>
>> Dear Kwang,
>>
>> Thank you very much for this explanation. Actually, it works quite
well
>> with the ThermalChimney object. Correct me if I'm wrong but it
requires
>> to have a ZoneInfiltration object in the zone to be cooled down (it
is
>> not written in the manual...)
>> Therefore, it is impossible to use this in addition to
AirflowNetwork
>> objects since they automatically desactivate ZoneInfiltration
object...
>>
>> So I guess unless I find a way to represent well the chimney
algorithm
>> with Airflow Network object I cannot try to compare windows natural
>> ventilation against windows+chimney natural ventilation.
>>
>> I had another issue: There are holes in other parts of the building
and
>> it seemed to mess with the airflow calculation of the zone I was
>> studying. So, the mass balance of the network is set at the building
>> level right? Because I had weird airflow through my ceiling although
it
>> does not connect with outside. Isn't it some numerical balancing the
>> software uses to reach building's global balance?
>>
>> Thanks a million!
>> Aymeric
>>
>> --- In EnergyPlus_Support@ yahoogroups. com, "Kwang Ho
Lee" <kwhlee@>
>> wrote:
>> >
>> > Dear Aymeric,
>> >
>> > A little mis-explanation in my previous email. The solar
radiation
>> does
>> > peak at noon (of course!), but the natural ventilation caused
by the
>> > thermal chimney does not necessarily peaks at noon due to the
sotrage
>> > effect of constructions including chimney absorption wall.
>> >
>> > Going back to your question below, EPlus Zone:ThermalChimney object
>> > assumes that all the natural ventilation airflows induced by
the
>> chimney
>> > are replaced by the "infiltration" . After EPlus
calculates the
>> enhanced
>> > ventilation airflow due to the chimney, the office space (in
your
>> case)
>> > would act like it is having the Zone:Infiltration object. So,
the
>> window
>> > opening won't have big impact on the chimney airflow.
>> >
>> > Again, I don't have enough experience with AirflowNetwork
object, but
>> I
>> > believe that it doesn't automatically calculate all the key
algorithm
>> > needed to predict the thermal chimney performance such as
thermal
>> > gradient and enhanced air volume, etc. (You need to doublechek
the
>> > documentations. Maybe I am wrong)
>> >
>> > Regards,
>> >
>> > Kwang
>> >
>> > > yes it means chimney temperature.
>> > > And indeed, in my model, when the office zone that is
adjacent to
>> the
>> > > chimney does not have opened windows, the natural
ventilation
>> flowing from
>> > > the office to outside via the chimney does peak around
noon.
>> > >
>> > > But to be realistic, I wanted to open office's windows
(20% of their
>> area)
>> > > so that I can quantify the natural ventilation flow rate
increase if
>> I use
>> > > the chimney to boost it, i.e I try to compare a single
sided
>> ventilation
>> > > (just the window is opened) with a cross ventilation
assisted by the
>> solar
>> > > chimney (window opened and solar chimney opened).
>> > >
>> > > In the second case, it does increase the ventilation rate
but
>> temperature
>> > > decrease in the office is not as much as this Pr would
expect + when
>> > > windows are opened airflow rate peaks at night because in
the
>> airflow
>> > > network calculation it seems that windows keep a dominant
role with
>> their
>> > > large vertical opening gravitational flow.
>> > >
>> > > I know all of this is a bit confused, I hope it is clear
enough...
>> > >
>> > > I will try with the thermalchimney object. Do I have to
remove the
>> airflow
>> > > network object from the chimney zone to use the
thermalchimney
>> object?
>> > >
>> > > Thanks, great help!
>> > > Aymeric
>> > >
>> > > --- In EnergyPlus_Support@
yahoogroups. com, "Kwang Ho Lee" <kwhlee@>
>> > > wrote:
>> > >>
>> > >> Dear Aymeric,
>> > >>
>> > >> Based on my experience, the natural venilation caused
by the
>> thermal
>> > >> chimney does not always peak at noon. I observed many
cases peaking
>> in
>> > >> the afternoon (1 ~ 3pm) when the solar radiation ramps
up.
>> > >>
>> > >> In "forced ventilation is proportional to room
temperature" , the
>> room
>> > >> temperature means the thermal chimney zone temp, not
the office
>> space,
>> > >> right?
>> > >>
>> > >> Regards,
>> > >>
>> > >> Kwang
>> > >>
>> > >>
>> > >> > Hi Pedro,
>> > >> >
>> > >> > Thanks a lot for your help. do you think the
airflow network
>> object is
>> > >> > better or not as good as using Thermalchimney
object?
>> > >> >
>> > >> > Another thing, below is the comment of a university
professor:
>> > >> > "in the case of solar chimney, air flow
increases with solar
>> radiation
>> > >> and
>> > >> > temperature of the plate in the chimney. In such
case, air flow
>> > >> velocities
>> > >> > increase to maximum value at noon and decreases
again in the
>> > >> afternoon.
>> > >> > This means that forced ventilation is
proportional to room
>> temperature
>> > >> > which increases to maximum at noon. For that, I
strongly believe
>> that
>> > >> > there is some difference between the chimney we
are using and
>> that
>> > >> used by
>> > >> > the simulation software"
>> > >> >
>> > >> > I believe the guy is mistaking between the fact
that the airflow
>> is
>> > >> > proportional to chinmney temperature and
proportional to the
>> > >> temperature
>> > >> > difference between chimney and outside... What do
you think?
>> > >> >
>> > >> > Thanks again!
>> > >> > Aymeric
>> > >> >
>> > >> > --- In EnergyPlus_Support@
yahoogroups. com, Pedro Peixeiro
>> > >> > <pedro_peixeiro@ > wrote:
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Hello.
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> My experience, I modelled a DSF using an
independent zone for
>> the
>> > >> >> middle cavity. It is important to model the
natural ventilation
>> using
>> > >> >> the AirFlow network objects to take advantage
of a better
>> simulation
>> > >> of
>> > >> >> the effects of pressure difference between
inlet/outlet due to
>> wind
>> > >> >> effect and temperature rise. Even so, it is
very hard to
>> simulate
>> > >> >> natural ventilation in these types of
building elements,
>> specially
>> > >> the
>> > >> >> air flow. My results
>> > >> >> were not entirely accurate, and I am still to
do some more
>> trials on
>> > >> >> E+.
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> One thing you can do to improve your results
is 1. create
>> independent
>> > >> >> zones for the inlet and outlet of the chimney
so to introduce
>> the
>> > >> right
>> > >> >> pressure coefficients of each one of these
(experimentaly
>> observed);
>> > >> 2.
>> > >> >> change the wind
>> > >> >> pressure coefficients of the outdoor surface
side of the chimney
>> so
>> > >> to
>> > >> >> aproximate your air flow results to the
experimental
>> > >> >> data, and thus obtain a better funcionality.
Unfortunately, #2
>> might
>> > >> be
>> > >> >> a
>> > >> >> bit laborous trial and error attempt. As far
as the temperature
>> > >> gradient
>> > >> >> is concerned, you can divide your chimney into
several vertical
>> > >> zones,
>> > >> >> or use the Room Air Models to try to find a
good aproximation
>> (note
>> > >> that
>> > >> >> the larger the gap depth and width is, the
less accurate will be
>> the
>> > >> air
>> > >> >> flow transition between vertical zones).
>> > >> >>
>> > >> >> Pedro.
>> > >> >>
>> > >> >> To: EnergyPlus_Support@
yahoogroups. com
>> > >> >> From: aymericnovel@
>> > >> >> Date: Tue, 16 Mar 2010 10:26:57 +0000
>> > >> >> Subject: [EnergyPlus_ Support] Thermal
Chimney modelling method
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Dear all,
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> I am struggeling to know whether or not I did
simulate properly
>> a
>> > >> solar
>> > >> >> chimney. It is in Jerusalem climate.
>> > >> >>
>> > >> >> I first modelled a zone adjacent to the
office I want to cool
>> down. I
>> > >> >> positionned a low opening on the partition
wall separating the
>> two
>> > >> >> zones. This wall is of course composed by a
structural part,
>> here
>> > >> >> concrete, 2.5cm polyurethan board insulation
and a black
>> selective
>> > >> metal
>> > >> >> plate. The outer wall of the chimney is a
glazed wall with an
>> upper
>> > >> >> opening.
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Although it seems to work logically, it
doesn't match
>> experimental
>> > >> >> results. Basically it seems it doesn't
enhance enough the
>> natural
>> > >> >> ventilation. ..
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Using this method, I certainly don't take
into account the
>> > >> temperature
>> > >> >> gradient within the thermal chimney, right?
Is it more reliable
>> to
>> > >> use
>> > >> >> the object Zone:ThermalChimney ?
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Plus, an additional problem I can't explain
is that I get some
>> > >> massflow
>> > >> >> through ceilings although I do not activate
infiltration
>> > >> calculations. ..
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> If anyone has experience modelling thermal
chimney, I would be
>> happy
>> > >> to
>> > >> >> know more about that!
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Thanks a million
>> > >> >>
>> > >> >> Aymeric
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> ____________ _________ _________ _________
_________ _________ _
>> > >> >> Hotmail: Trusted email with Microsoft's
powerful SPAM
>> protection.
>> > >> >> http://clk.atdmt.
com/GBL/go/ 210850552/ direct/01/
>> > >> >>
>> > >> >
>> > >> >
>> > >> >
>> > >>
>> > >
>> > >
>> > >
>> >
>>
>
>
>