[Bldg-sim] Water-Side Economizer

D G colbns0rpid at gmail.com
Mon Apr 28 07:32:37 PDT 2008


I think the unanswered question you're referring to is mine.  We were trying
to simulate Trane Self-Contained Air handlers (SWUDs).  McQuay and Carrier
also make these systems.  You may not be referring to this type of system.
SWUDs use an internal economizer on floor's air handler which uses condenser
water when OA Temp drops below a certain setpoint.  The waterside economizer
option in DOE 2.2 is not the same as the SWUD system, I think.  I believe
this can be simulated with equest using a seperate cooling tower and an
add-on indirect evaporative cooler.

In real life the WSE is controled by condenser water temperature.  In DOE
2.2 I believe the control temperature a constant user specified limit.

We never finished the model we were working on so I'm not sure how to
control the cooling tower.  Real SWUDs tie into the building's condenser
water loop.  So I assume you can use the same schedule on the evaporative
cooler's cooling tower as the CT for the DX systems.  Another energy firm
modeled the building and we did the base building design.  We are new to
energy modeling so every meeting we had with the Architect and other design
personnel we would pick the modelers' brains as to how they modeled these
systems.  Please let me know when you get the final model to work.

DG
------------------------------
*From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Xu, Xiaowei
*Sent:* Thursday, April 24, 2008 3:06 PM
*To:* bldg-sim at lists.onebuilding.org
*Subject:* [Bldg-sim] Water-Side Economizer

Hi,

I have some questions about the Water-Side Economizer simulation in eQUEST.
I searched for this topic in the simulation group archive. It seems that
someone also had the problems with the simulation of water-side economizer
but no one answered it.



Currently I am working with an office building with DX coil system. The
proposed design uses the water side economizer because the air-side
economizer is not available. I added the water side economizer into the
existing condenser water loop. But the simulated result showed the system
with water-side economizer had more energy consumption than the system w/o
economizer because of more energy consumed by the fan, pump and cooling
tower.



Here is question about the simulations setting in eQUEST for water-side
economizer:

1. what loop should the water-side economizer be attached to: the current
existing condenser water loop or a new condenser water loop?

I tried both and got quite different results. None of them saved energy.

2. what temperature in eQUEST should be used for control the water
economizer? If the current existing condenser water loop is used, how to
control the temperature both for the water-side economizer and the DX coil?

3. How to set the control for the cooling tower?



Any suggestion would be much appreciated.



Thanks.



*Xiaowei Xu***

*Engineer*          **

* **FLACK** **+** **KURTZ*

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*http://www.flackandkurtz.com*

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*xiaowei.xu at ny.fk.com

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