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[EnergyPlus_Support] Re: validation of extensive coefficients use
Thank you,Brent/(Fred), for your elaborated explaination. So can I
assume that the "normalization" means a ratio of a real-condition
parameter to a rated-point one? Then how about curves of Electric
Chiller, WindAC,Direct-fired absorption Chiller? Are they called
normalized curves?
John
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Griffith, Brent"
<brent_griffith@n...> wrote:
>
> John,
>
> Keep in mind that there are at least two possible "policies" for
curve-fits. One option is to use curves that are normalized with
respect to capacity (or efficiency) at a single operating point.
The other is to use curves that directly fit the capacity/efficiency
data without normalization. It is not unreasonable practice to use
normalized curves for components that have a different nominal
capacity or efficiency than the one used to produce the curves.
Clearly it is better to use performance curves that apply to the
unit being modeled, but this isn't always practical. On the other
hand, direct performance curves (that aren't normalized) are
basically limited to the original unit and cannot be used to model
components with a different size or nominal performance.
>
> Developers have different opinions on which is the best way to
go. The normalized-curve group want curves to be more general so
that one can easily adjust equipment capacities when doing a
simulation study. The direct-curve group are more leary of the
pitfalls of abusing curves and want to force the user to use curves
that match the component. I am not sure if it is true across the
board, but curves tend to be of the normalized type in EnergyPlus.
So it is not blatently wrong to reuse such curves for different
capacities. However, do not assume that the example files that ship
with EnergyPlus represent best modeling practice. It is better to
think of them as test and demonstration files.
>
> Brent
>
> -----Original Message-----
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]On Behalf Of
deserteagle_zhou
> Sent: Tuesday, October 11, 2005 4:13 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] validation of extensive coefficients
use
>
>
>
> Hi,there,
>
> Components, i.e., chiller, fan, etc, are defined according to a
> performance curve-fit policy. Curves, however, often have
something to
> do with the real working conditions and an equipment capacity. I
think
> users are not supposed to use directly the same coefficients as
before
> after the equipment capacity has been changed. That means we 'd
better
> not use directly the curves and parameters in E+ example files
directly
> unless we cannot get the data from the equipment producer.
> Is this understanding right or not?
>
> Another question is whether the object SINGLE DUCT:VAV REHEAT can
deal
> with heating condition alone in a zone without a company heating
device
> (such as a baseboard heater), especially in a cold area?
>
> Thank you.
> John
>
>
>
>
>
>
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