[Bldg-sim] Chilled Beams

Steven Savich ssavich at systemswestengineers.com
Mon Dec 31 12:01:07 PST 2007


Greetings Everyone, and Happy New Year.

 

I'd like to revive a discussion on Chilled Beams from 2006 from the BLDG-SIM
archives to see if anyone has had some additional insights into the modeling
problems involved.  I've reprinted (one of) the relevant threads below.

 

I'm currently modeling a building in eQuest that has active chilled beams as
an alternate.  To summarize my understanding of the prior consensus:

1)     The chilled beams can be modeled as either a PIU OR FCU system.

2)     Use OA-FROM-SYSTEM to pass the required outside air to individual
room, specifying a central dedicated ventilation air handler.

3)     Check SSN reports to make sure that there's no condensation on the
chilled beams.

4)     Check turndown ratio and match induction rate to the profile of the
beam.

 

Some questions -

One person said the induction ratio doesn't really matter.  It this true?

Items 3) and 4) below from Graham Carter, it would be really helpful if
those comments were fleshed out a bit more.  I would assume that this would
entail making a set of dummy spaces that have the latent loads of the actual
spaces.  Would these be attached to the chilled beams system, or to the
"ventilation only" air handler?

 

Thanks,

Steven

 

Steven Savich

Systems West Engineers

411 High Street

Eugene, OR  97401-2427

(541) 342-7210

(541) 342-7220 (fax)

 

 

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 <mailto:perickson at xxxxxxxxxx>  

To: BLDG-SIM at xxxxxxxx 

Cc: Eric.Yang at xxxxxxxxxxxxxx 

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 xxxxxxxxx> 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
 <blocked::http://www.ibece.com/> 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: 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
 <blocked::http://www.ibece.com/> 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 xxxxxxxxxxxxxx] 
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 xxxxxxxxx] 
Sent: Monday, September 11, 2006 6:36 PM
To: Eric Yang; BLDG-SIM at xxxxxxxx
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
 <blocked::http://www.ibece.com/> 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 xxxxxxxx [mailto:BLDG-SIM at xxxxxxxx] On Behalf Of Eric Yang
Sent: Monday, September 11, 2006 2:34 PM
To: BLDG-SIM at xxxxxxxx
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 xxxxxxxxxxxxxx 

 <http://www.smithgroup.com/> www.smithgroup.com

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