Re: [EnergyPlus_Support] Ventilation

["Richard J. Liesen" <rliesen@xxxxxxxx>]

Hello Carmen,

I do not think you will be able to use the Purchased Air system to 
accomplish what you want; you will have to specify a system with a Mixing 
Box.  If you look at examples using a Mixing Box you will see that the, for 
a lack of a better term, Outside Air node has to be specified and 
explicitly set to have the outside environments conditions specified for 
that node.  This provides a lot of flexibility for that inlet node in the 
Mixing Box to be specified to other system nodes in your simulation, such 
as the exhaust air node from another zone.  I know that you said this 
atrium zone is not of interest to you, but you will probably have to 
simulate some type of zone and using Purchased Air have it control this 
zone of non-interest to 25C.  Since this zone is of non-interest to you it 
can be any simple zone model which conditions the air to the desired 25C 
condition.  Then using an exhaust air outlet node from that zone as your 
inlet node to the Mixing Box to get your 25C inlet air conditions.  You 
will of course have to make sure that you satisfy Continuity.  Make sure 
you turn on the Node reports for that inlet node for temperature, mass flow 
rate, etc. to ensure that you are getting the inlet conditions that you 
desire.

You might make a suggestion to the EnergyPlus Development Team, whoever 
that is, to create another node object like the OUTSIDE AIR INLET NODE LIST 
which puts constant user specified conditions on a node to handle cases 
like this.  It could be looked at as the system equivalent to Other Side 
Coefficients.

Thanks Richard Liesen


At 05:20 AM 7/8/2004, carmen herrero prada wrote:
>Hello all,
>
>I have a problem. I am simulating a comercial building
>just to get cooling loads, so using purchased air.
>This building is placed inside an atrium which indoor
>air is maintaned at 25-26 ºC all year by an air system
>i am not interested in. So, I have used other side
>coefficient to indicate energyplus that my exterior
>walls (except one) have a constant exterior air
>temperature and film coefficient. But my problem is
>that I need to define ventilation flow rates for my
>zones, and this ventilation air is taken from the
>surrounding environmet, so it is always air at 25-26
>ºC. I don´t know how to define it since i am running a
>whole year simulation with the Madrid weather file
>(the building has got one facade facing outside
>environment), so I presume the system is taking the
>air at Madrid exterior temperature each time step,
>which is not the real behaviour.
>
>Any suggestions?
>
>Thanks a lot.
>
>Carmen.
>
>
>
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