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Re: [EnergyPlus_Support] mutizone in a single space

I apologise- my last response was meant for another thread with regards to holes & ventilation-

Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions
120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951


On Tue, Aug 7, 2012 at 11:43 AM, Jeremiah Crossett <jcrossett@xxxxxxxxxxxxxxx> wrote:
In design builder- if you use the calculated natural ventilation than your  "vents/doors" will be modulated based on your settings and will automatically create your energy plus air flow network. I suggest you first do an external CFD analysis of your building model, then place your vents in locations of high air pressure & velocity, then after placing your vents in areas set them to open based on inside to outside temperature differences and enthalpy differences as to assure your air flow will be beneficial. Then run your Energy Plus model in Design Builder while checking the HVAC sizing summery report output. Check your peak cooling date/time, then re-simulate with sub-hourly output for only the peak cooling day, and then import your Energy Plus results into design builder CFD for the time of peak noted from the energy plus run- this will produce a visual snap shot of the maximum effectiveness of your natural ventilation strategy. 

All the best-

Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions
120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951


On Tue, Aug 7, 2012 at 10:43 AM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

Hi, Long
It depends on what you wanted to study.
The best way to divide the room is to use the configuration of the 5-zone model in the example files.
In this way, the external walls are all in one piece.  The core zone has the average temperature of the other four zones. However, it may not be exactly the same as that for the large one room.
If you only wanted to know which side of the room is hotter or cooler due to external sources, simply report the inside surface temperature values of the walls.  These values should be different from the zone mean air temperature.  However, the solar load through windows is not  easy to compare.  The radiation may enter one window and leave by the other windows.

Unless you are using AFN objects, there is no air flow in the EPlus simulation.  An AHU does not actually force air into the zones.  The amount of heat involved with the volume which would be moved in one time step is transferred in to and out of the zone.  The inlet air is at the supply air temperature, and the exhaust air is at the return air temperature.  The moisture content is also treated in a similar way.
Therefore, if you have holes, doors in the model, it will not make any difference.
The use of IRtransparant wall allows user to divide a space into more zones, so that more equipment may be defined in EPlus simulation.  The two zones of a large room may now be served by two AHU's. (or two window units.)  All radiant components are converted into IR and exchange across the IR wall.  I assume that when IR is balanced, the room temperature would be the same. 
I used the IR wall mainly to close any large openings to complete a zone boundary.
I assume that zone mixing may be used with the IR wall to maintain a temperature difference between the zones.  Then why use IR wall at all, to do visible to IR conversion, etc. and then over ruled..
For the same process, infiltration and ventilation may be applied to any zone without any openings.    All holes, windows and doors will not have real air flow through them.  DoorOpen schedule may be used to chnge the air flow rate of infiltration.  The user must know which imaginary 'door' (zone) is being used.

For daylighting simulation, I think you must have another window at the inner zone.  IR wall does not make sense.

 Dr. Li  


To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: ltb.phan@xxxxxxxxx
Date: Mon, 6 Aug 2012 20:27:28 +0000

Subject: [EnergyPlus_Support] mutizone in a single space

Hi, All

I have a single room space, and I'd like to divide this single zone into multiple sub-zones to account for their different thermal properties. How would I specify the boundary conditions among those sub zones. I've read about air wall, but my big concern is if I use air wall, would the air exchange and thermally interact between subzones? or it is just a tool used for radiant/daylight calculation. Are there any other suggestions? Thanks a lot.



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