[EnergyPlus_Support] Re: Thermal Chimney modelling method

["Wonjun" <lesthesia@xxxxxxxxxxx>]

I can't understand the compatibility between Thermal Chimney and Airflow Network. So I should make all these things clear by your help.


I tried to model a building applied cross ventilation boosted by Thermal chimney. So there are openable windows attached on interanl walls to facilitate wind flow. 
I thought this can be done by using 2 objects as I stated above(Thermal chimney and airflow network.). 
But if it's not possible as you said, how I can model this idea in E+? I know one thing that I should use Airflow Network because of cross ventilation. 
The problem is the boosted flow rate by absorbing of solar radiation which is the key of this idea, but I don't know how to solve this.  
And I don't know how can I can take into consideration the "Width of the Absorver Wall" in the "Zone Thermal Chimney."   

Need your help. 


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@...> wrote:
>
> The AirlfowNetwork model does not support thermal chimney right now. The combined capability is listed in a wish list.
> 
>  
> 
> Lixing 
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Fernando Sa
> Sent: Friday, March 19, 2010 7:26 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] Re: Thermal Chimney modelling method
> 
>  
> 
> 
> 
> 
> 
> 
> 
> I'm working with Thermal Chimney in Brazil, but i'm not working with zone:thermalchimney because this object is incompatible with airflownetwork, and is limited to model studied for Ong (2003) with vertical chimney, i prefer to work with airflownetwork only.
> 
> --- Gio 18/3/10, Kwang Ho Lee <kwhlee@...> ha scritto:
> 
> 
> Da: Kwang Ho Lee <kwhlee@...>
> Oggetto: Re: [EnergyPlus_Support] Re: Thermal Chimney modelling method
> A: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Data: Giovedì 18 marzo 2010, 14:14
> 
>   
> 
> 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. <http://clk.atdmt.com/GBL/go/210850552/direct/01/>  com/GBL/go/ 210850552/ direct/01/
> >> > >> >>
> >> > >> >
> >> > >> >
> >> > >> >
> >> > >>
> >> > >
> >> > >
> >> > >
> >> >
> >>
> >
> >
> >
>




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