Hi, Jean
If the kitchen air is exhausted to the enveronment air tank, the kitchen zone return air is reduced, therefore there will be less air for the OA mixer relief node. This is another interesting point. All the OA mixer, infiltration and ventelation paths are also through mixer and splitter pair in the OA tank.
With AFN, the pressure change (wind velosity) is added to the tank.
If the exhaust air is larger than the OA inlet, the air must come from the leaks.
In practice, you will hear the speed of the exhaust fan chaning, as you open and close the kitchen door.
Un-balanced air between zone is handled by zone mixing, or plenum.
That was the reason why I said you can say 100% fresh air from OA by making inlet flow rate the same as the fan rate. In practice, it is not easy to do. You can specify min. rate of OA equals to max flow rate of the fan. The return air amount is not known or specified, and the zone exhaust and inlet can be from other paths of the OA tank.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Sat, 24 Sep 2011 11:53:04 +0000
Subject: [EnergyPlus_Support] Re: OutdoorAir:Mixer questions
Hi Dr. Li,
I find the "environment tank" analogy very interesting. Particularly, that the relief air is equal to the ODA flowing into the ODA system. In real life as in the simulation more than 1 system may be present, e.g. AHU serves supply air to both office and kitchen zones, but the kitchen has it's own fan:zoneexhaust to the outdoors.
In this case the relief air of the AHU is not equal to the supply air, but the "environment tank" remains balanced as the kitchen also exhausts to it.
Now when kitchen makeup air is the combination of supply air and infiltrated via the office zones, it becomes tricky. As the demands of the kitchen and the offices are independant, it may occure that the flow is unbalanced at any possible timepoint. Should one not wish to use an AFN crack between kitchen and office and office and outdoors, is there a way you would suggest to address the unbalanced flow?
e+ simply issues the warning that the unbalanced air is not flowing in from outdoors and may decrease the accuracy of results.
I find the "environment tank" analogy very interesting. Particularly, that the relief air is equal to the ODA flowing into the ODA system. In real life as in the simulation more than 1 system may be present, e.g. AHU serves supply air to both office and kitchen zones, but the kitchen has it's own fan:zoneexhaust to the outdoors.
In this case the relief air of the AHU is not equal to the supply air, but the "environment tank" remains balanced as the kitchen also exhausts to it.
Now when kitchen makeup air is the combination of supply air and infiltrated via the office zones, it becomes tricky. As the demands of the kitchen and the offices are independant, it may occure that the flow is unbalanced at any possible timepoint. Should one not wish to use an AFN crack between kitchen and office and office and outdoors, is there a way you would suggest to address the unbalanced flow?
e+ simply issues the warning that the unbalanced air is not flowing in from outdoors and may decrease the accuracy of results.
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
__,_._,___