[bldg-sim] VAV vs. Constant volume cooling energy

Zhou, Anna annazhou at geopraxis.com
Mon Apr 12 17:55:26 PDT 2004


Mike,

I did experiment by using a 5-zone 1-story building, assigning each zone to
a system in both In the PSZ system case and the PVAVS system case and
resetting the supply air temperature to a higher upper bound to avoid
reheat. it does bring down the cooling energy consumption of the PVAVS, but
the total energy consumption is still higher (each month) than the PSZ.
This is when both PSZ and PVAVS are using OA-temp economizer.

Then, by disable the economizer, the cooling energy consumptions from PVAVS
and PSZ are brought closer to each other. This shows as if the control of
PVAVS in DOE2 tries to reduce air flow first instead of using more outside
air when the outside is cool.But still the PVAVS cooling energy is always
slightly higher than PSZ (under California climate zone 1).I just cann't see
a case that PVAVS uses less energy than PSZ.

Also, doe this say when there are economizers,it's better to use constant
volume rather that variable volume? What's the typical control sequence of a
VAV system among: volume decreasing, temperature reset and economizer? Can
we specify in DOE2 the sequence we want?

Thanks for your reply.

Anna


-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Mike
Roberts
Sent: Monday, April 12, 2004 4:16 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] VAV vs. Constant volume cooling energy


Anna,

A PSZ (Packaged Single Zone) system is constant volume, but only has to cool
when the space calls for cooling.  A VAVS system cools the air all the time
(or may use an economizer part of the time), then reheats the air to the
temperature the space requires.  You can improve on this by resetting the
cold deck temperature, but will probably not get your cooling below a single
zone system.  For comparison, try a RHFS system.  That is a constant volume
system, but cools all the air, then reheats it to satisfy the zone.  It will
generally use more cooling than the VAVS system.

Both DOE-2.1 and DOE-2.2 have some fairly extensive documentation on
controls, related to how the programs control real world systems.

Mike

-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Zhou, Anna
Sent: Monday, April 12, 2004 6:34 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] VAV vs. Constant volumn cooling energy


The simulation software was DOE2.2.

-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Zhou, Anna
Sent: Monday, April 12, 2004 3:19 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] VAV vs. Constant volumn cooling energy


Hi,There

When doing simulation, I noticed that the cooling energy consumption from a
variable air volumn system (VAV,PVAVS) is always larger than that of a
constant volume system (PSZ). Did anybody have this problem, too? Can
anybody tell me what's the possible cause of this?

Thanks a lot.

Anna

======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE at GARD.COM

======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE at GARD.COM



======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE at GARD.COM

======================================================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM



More information about the Bldg-sim mailing list