[BLDG-SIM] Waterside Economizer

[Fred Porter]

The lack of a WS CW-to-CHW economizer component in DOE2.2/PD is one of the
reasons I'm still using DOE2.1.

When I was trying to use 2.2, I tried the following to mimic a flatplate
tower-CHW HX in parallel with chillers:
    I created a virtual chiller with .05 kW/ton.
    I think I also created a separate CW loop with a lower CW setpoint.
    To dispatch this capacity, I used some kind of load assigment, or loop
control statements or something.

As I recall, I experienced crashes while DOESIM was running, because of curves
that couldn't be evaluated, or divide by zero, or... This experience was awhile
ago.

One could also create "virtual" chiller curves incorporating greatly reduced
kW/ton at low CW temps, but the extreme non-linearity might be hard to handle.

None of this seems very satisfactory for modeling a common component of
efficient HVAC systems in the latest version of a widely-used advanced hourly
simulation program.

Maybe JJH would weigh in with a suggestion.

IEC wrote:

> Does anyone know the best way to model a waterside economizer in PowerDOE?
> The building uses economizing capacity when the condenser water temperature
> is approximately 70°F or less.

Do you have separate CW coils on the OA, or very, very high CHW delta Ts?

> I would appreciate any help.  Thanks.
>
> Morgan Stewart
> Graduate Student
> Virginia Tech
>
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--
Fred W. Porter
Senior Engineer
Architectural Energy Corp.
2540 Frontier Ave. Suite 201
Boulder CO 80301
email: fporter at archenergy.com
fax: 303-444-4304

office: 303-444-4149 x225
mobile: 303-748-4536


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