[BLDG-SIM] Active Chilled Beam Model
Graham & Megan
hamnmegs at ozemail.com.au
Tue Sep 12 14:35:49 PDT 2006
This is a good discussion, I am glad others are trying to find work arounds as the humidity control and central heating aspects are not straight forward.
I am not fmailiar with the fan energy problems, but I am familiar with the following:
1) There is a lower limit on CHW DT across the chiller which I believe is 6DegF.
2) The OA-FROM-SYSTEM is the way to go in EQuest/2.2. TAS, Apache and I suspect other programs allow the heating / humidity control to be handled more easily and accurtely but fall down on the waterside.
3) The OA-FROM-SYSTEM cannot 'see' the zones you are passing the air to so therefore off-coil temperatures cannot be directly controlled from the zone unless you replicate a dummy building that mimics your actual model's latent loads etc.
4) Further to #3 the OA-FROM-SYSTEM cannot see the zone heating demands thus space heating must be local by baseboards or by a 4-pipe IU/FCU.
5) Given above I have tended to se up my OA-FROM-SYSTEM as a SZRH system with the cooling coil off-coil controlling to an outdoor air reset schedule to dehumidify and the zone heating coils reheating to maintain a minimum zone supply temperature (nominally 15C). In Australia we use this configuration as we have warm to hot and humid climates with a small heating load in comparison to most North American climates. In winter the central heating coil (zone coil in this case on a SZRH) would heat to satisfy zone of greatest heating demand and other zones would recool. Reheat and recool sounds inefficient but when the heating is done with CW heat recovery and periods of simultaneous heating and cooling are in cooler months when plant effcieincy is at a maximum, the whole system is actually quite efficient.
6) I then iterate on the outdoor air reset schedule and observe humidity levels in key zones to satisfy myself that I am getting space dewpoint control.
7) Ultimately with a chilled beam system that is most sensitive to space dewpoint control this is still only a good approximation that is time consuming to ensure it is right.
I mentioned last week that the EQuest/2.2 team could fix this up (IU system with no OA-FROM-SYSTEM, dewpoint contrl and central heaing / reheat) if the $ could be found - keep in mind we enjoy freeware. Speaking with Jeff Hirsch over the years we aren't talking a lot of money but it is too much for me to justify paying 100%. Anyone feeling generous or like me, frustrated at the time consuming work arounds, please contat Jeff and/or myself as this enhancement would extend the application of EQuest/2.2 dramatically (from my point of view).
Regards,
Graham Carter
----- Original Message -----
From: Paul Erickson
To: BLDG-SIM at GARD.COM
Cc: Eric.Yang at smithgroup.com
Sent: Wednesday, September 13, 2006 12:23 AM
Subject: [BLDG-SIM] Active Chilled Beam Model
Eric,
As Peter stated, an induction unit can have a dedicated system supply source (for Trace it is OA; for eQUEST/DOE-2 you specify source...OA or rom a chosen AHU). The same is true with the fan coil unit.
For DOE-2.2/eQUEST specifically, there are a few of snags that one runs into. One, the induction ratio doesn't really matter...play around and you'll see. Two, DOE-2 doesn't seem to account for the fan energy used to pull off the CFM that goes to the beams...I'd love for someone to prove I'm wrong. Three, I've had difficulties with loop temperatures and delta T for the loops...i.e. DOE-2 didn't seem to like the higher water temps going to the IU/FCU. I'd like to hear feedback if someone else got around this.
Trace had some similar drawbacks...I'll work on recalling them.
Paul
>>> "Peter Simmonds" <peter.simmonds at ibece.net> 9/12/2006 8:48 am >>>
Peter Simmonds Ph.D.
Associate
IBE Consulting Engineers
14130 Riverside Drive Suite 201
Sherman Oaks, CA 91423
p: (818) 377-8220
f: (818) 377-8230
m: (818) 219-1284
IDEAS FOR THE BUILT ENVIRONMENT
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From: Peter Simmonds
Sent: Monday, September 11, 2006 3:47 PM
To: 'Eric Yang'
Subject: RE: [BLDG-SIM] Active Chilled Beam Model
OK so you are talking about an active beam and not a static beam, right. Then you need an outside air supply to be incorprated into the conditioning system, so I guess the induction unit will suffice, just check the minmum turndown ratio and check the induction rate to match the profile of the active beam.
Peter Simmonds Ph.D.
Associate
IBE Consulting Engineers
14130 Riverside Drive Suite 201
Sherman Oaks, CA 91423
p: (818) 377-8220
f: (818) 377-8230
m: (818) 219-1284
IDEAS FOR THE BUILT ENVIRONMENT
This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure, or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
--------------------------------------------------------------------------
From: Eric Yang [mailto:Eric.Yang at smithgroup.com]
Sent: Monday, September 11, 2006 3:40 PM
To: Peter Simmonds
Subject: RE: [BLDG-SIM] Active Chilled Beam Model
Thanks for your inputs. How about the air which is induced into the beams? For example, I supply only 105 CFM per beam, but I will have around 300 CFM total supply air.
Eric
--------------------------------------------------------------------------
From: Peter Simmonds [mailto:peter.simmonds at ibece.net]
Sent: Monday, September 11, 2006 6:36 PM
To: Eric Yang; BLDG-SIM at GARD.COM
Subject: RE: [BLDG-SIM] Active Chilled Beam Model
Very simple. Model the chilled beam as a fan coil for cooling only and remove the associated fan power.
Peter Simmonds Ph.D.
Associate
IBE Consulting Engineers
14130 Riverside Drive Suite 201
Sherman Oaks, CA 91423
p: (818) 377-8220
f: (818) 377-8230
m: (818) 219-1284
IDEAS FOR THE BUILT ENVIRONMENT
This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure, or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
------------------------------------------------------------------------
From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM] On Behalf Of Eric Yang
Sent: Monday, September 11, 2006 2:34 PM
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] Active Chilled Beam Model
Greetings
I am seeking for any suggestions or input on the model of active chilled beam system. In my previous Trace model, it can not handle it very well by induction system. I am very curious to get inputs and helps from other folks. Thanks in advance.
Eric
Eric Yang
Mechanical Engineer, LEED.A.P.
SmithGroup
1850 K Street, NW, Suite 250
Washington, DC 20006
t 202.974.4555 (direct)
f. 202.974.4500
eric.yang at smithgroup.com
www.smithgroup.com
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