Re: Optimisation of Chilled Water Storage System

[Fred Porter <fporter@xxxxxxxxxxxxxx>]

DOE2.2 models condenser pumps, and many strategies for chiller dispatch
explicitly.

Both 2.2 and 2.1 allow the entry of custom curves. Most chillers can be modeled
with a custom CURVE-FIT entered as points or coefficients. In DOE2.2 functions
will be available in the plant module to allow better modeling of interactions
between part load and condenser/chilled water temperatures that can only be
approximated in DOE2.1.

The big drawback of 2.2 is the omission of any provision for tower free cooling,
and a requirement that chillers and chiller/flat plate HXs operate in parallel;
never in series. Also the dispatch of chillers by the program seems a bit
arbitrary. I'm often trying to model something that doesn't quite fit into "the
box," they have made, a frustrating process.

I've never had the opportunity to use TRNSYS for a central plant, but the
advantages would be:
1) easily customized performance "maps," using interpolation instead of curve
fits, if necessary.
2) ability to define the flows as they actually occur using the various valve
and T-piece components.
3) ability to control flows, dispatch,  temperatures in ways that more closely
mimic the anticipated plant controls.

Unfortunately, it's hard to know if consideration of all of the above will
produce different results until the simulation(s) are done.

DOE2.2 should be out with functions now, but some legal hassles are holding it
up apparently.

Tianzhen HONG wrote:

> Thanks for all providing suggestions.
>
> DOE-2.1E can draftly model the plant energy including the chiller/CHW
> pumps/CT, I am not sure if condenser water pumps are considered. I found
> that the DOE-2.1E three types of chiller curves can't fit the Trane
> 1000RT/2000RT centrifugal chillers well. Hope DOE-2.2 has more curve types.
>
> Haven't tried modeling the CHW systems with TRNSYS mostly because we employ
> hourly simulations and transient effect is little. I guess detailed modeling
> of chilled water systems should be carried out with some detailed HVACR
> modeling package like SPARK or EnergyPlus.
>
> Cheers
>
> Tianzhen Hong