Re: [EnergyPlus_Support] Re: HP Coefficient Calculator High Error

Karen

On Thu, Jan 26, 2012 at 4:31 PM, Richard Raustad <RRaustad@xxxxxxxxxxxx> wrote:

If any of the independent variables are constant, load or source side, then the coefficients for that variable will be 0 and you will have to operate the system at that condition. In your case, you will have to operate the HP with a 70F load side air inlet temp. If you deviate from 70F, the answer will be inaccurate. Since always having a 70F inlet air temp during your simulation is unlikely, you need more data which shows you how performance changes with changes in inlet air temperature. Constant flow is OK since you can force the HP to operate at that flow rate, you just can't use these coefficients for a simulation with a different flow rate (unless you assume that the performance does not change at a different "rated" flow rate).

On 1/26/2012 4:23 PM, Chandan Sharma wrote:

Both load and source side have to vary.

On 1/26/2012 4:20 PM, luke_dorna wrote:

The cut sheet I have has constant load side air temp and flow with varying source side water flow and temp. When you say these cannot be constant, do both load and source side have to vary, or just the source?

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Chandan Sharma <csharma@...> wrote:
>
> Hi Luke,
>
> In the "Catalog Data" tab, the data points must have varying inlet
> conditions which covers entire range of heat pump operation. There
> should be at least 6 data points and flow rates/temperatures columns
> must _not_ be constant.
> If the manufacturer has provided you correction factors to extend the
> performance data, it would help to generate more accurate coefficients.
> In general equation fit model is preferred over parameter estimation
> model and one of the reason is that curve fit coefficients are easier to
> calculate. Also, the curve fit model allows you to calculate
> coefficients for 410A.
>
> "Rated..." values in the CoeffCalculator tab also affect the curve fit
> coefficients.
>
> Hope this helps.
> Chandan
>
>
>
> On 1/26/2012 3:16 PM, luke_dorna wrote:
> >
> > I am currently trying to generate the equation fit coefficients for a
> > water to air heat pump cooling coil. Unfortunately, the
> > waterair_pe_cooling.xls file seems to be giving me an incorrect result
> > with average % of over 100.
> >
> > Has anyone run into a situation like this? It looks like can get a
> > better result from the parameter estimation method, however it does
> > not support 410a, which is the refrigerant from the design.
> >
> > Thanks,
> >
> > Luke
> >
> >
>
-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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