[Bldg-sim] CFD modeling for lab buildings

James V. Dirkes II P.E. jvd2pe at tds.net
Mon Aug 18 10:32:32 PDT 2008

Dear Vikram,
Although I know nothing about GC equipment, physics mandates that all energy
which goes into almost all mechanical / electrical devices becomes heat.
Your job is to a) figure out whether the heat ends up in the conditioned
space or elsewhere and b) figure out what the effective load diversity is
for your particular piece of equipment. (almost nothing operates 100% of the
time at 100% of its maximum energy.)
Forgive me if I'm too elementary here with a couple simple examples:
1) An exhaust fan motor imparts a certain amount of energy (its work energy)
to the exhaust air.  If the air ends up outdoors, that energy does not
affect the AC load.  In addition, the motor itself may be in the exhaust
airstream or outside it.  If it's in the airstream, the ~10% motor
inefficiency also ends up in the exhaust airstream.  If the motor is outside
the exhaust airstream, the ~10% ends up wherever the motor is located.
2) Similarly, an air handler fan motor imparts its work energy to the
airstream and therefore always becomes part of the AC load.  The motor
inefficiency, depending on the motor placement, may become part of the AC
load (or not).
A fine point in this consideration is that belt-driven motors always lose
~6-7% via the transmission (belt) system.  Most people forget about this.
I suspect that your GC equipment will dissipate all of its energy into the
space it occupies unless, for example, it is water-cooled, in which case the
water cooling system will remove some of the heat from the space in which it
is located.

The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653




From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Vikram Sami
Sent: Monday, August 18, 2008 1:04 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] CFD modeling for lab buildings

I'm curious if there are any published papers on CFD modeling of lab
equipment. I'm particularly interested in gas chromatographers. We are
working on a lab building with GCs and I would like to see what portion of
their considerable heat output is actually seen by the chillers. 


Vikram Sami, LEED AP 
Direct Phone 404-253-1466 | Direct Fax 404-253-1366 

1201 Peachtree Street NE, Suite 300, Atlanta, GA 30361 
Responsive Design . Technological Expertise . Exceptional Service 
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