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Re: [EnergyPlus_Support] DX Cooling Curves





Clarifying:
Does "Coefficients for EIR-FPLR = a + b- PLR + c- PLR2 + d-PLR3" get interpreted as:

Coefficients for EIR-FPLR = a + b * PLR + c * PLR^2 + d * PLR^3

On Fri, Mar 3, 2017 at 6:23 AM, Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Dear Joe,
This is fascinating and helpful information. After re-formulating for E+, I'm going to see what those Henderson curves look like.

In the meantime, and in case you missed it, there is some discussion on UnMet Hours here about how to get those curves to represent ASHRAE 90.1-specified part load performance.

Thanks for sharing this.

On Thu, Mar 2, 2017 at 10:14 PM, Joe Huang YJHuang@whiteboxtechnologies.com [EnergyPlus_Support] <EnergyPlus_Support@yahoogroups.com> wrote:
 

I'm going to chime in here too, because I'm currently working on a project to develop performance curves for newer types of HVAC equipment, albeit for DOE-2, but those curves have the same information but just a different formulation than those in EnergyPlus.

The person who's done the most work as far as I can see in HVAC equipment curves is Hugh Henderson in upstate New York (here's my shout-out to Hugh!).

From what I've learned, there is very little data on Part Load characteristics of HVAC equipment, so as a recourse these are calculated from first principles, the principles being the cycling rate of the equipment and the constant off-cycle parasitic electricity.  In an old 2000 paper by Hugh, Danny Parker, and me ("Improving DEO-2's RESYS routine: User Defined Functions to Provide More Accurate Part Load Energy Use and Humidity Predictions",  ACEEE Summer Study on Building Energy Efficiency, Asilomar CA.),  Hugh (who did most of the work) came up with the following EIR-PLR coefficents for various types of A/C:

         Coefficients for EIR-FPLR = a + b- PLR + c- PLR2 + d-PLR3

                    a                          b                       c                         d

Curves with Off-Cycle Power

"Typical AC" (Nmax=2.5, tau=60, pr=0.01)

0.0101858

1.18131

-0.246748

0.0555745

"Good AC" (Nmax=2.5, tau=60, pr=0.01)

0.00988125

1.08033

-0.105267

0.0151403

"Poor AC" (Nmax=3, tau=60, pr=0.03)

0.0300924

1.20211

-0.311465

0.0798283

Curves without Off-Cycle Power

"Typical AC" (Nmax=2.5, tau=60)

0.000352822

1.19199

-0.246716

0.0546566

"Good AC" (Nmax=2.5, tau=60)

4.2812e-005

1.09001

-0.103863

0.0138504

"Poor AC" (Nmax=3, tau=60)

0.000582243

1. 23565

-0.313841

0. 0780726

Since it's now been 17 years, you are free to question Hugh's statement at that time, "There is nt expected to be much difference between 
new and existing systems. Most research into part load issues were conducted in the 1970's and 1980's, though work at FSEC (Henderson 1990) 
and other places appear to confirm these earlier findings"  (Henderson et al. 2000)

The other caution is that I recall the EnergyPlus EIR-FPLR equation is the inverse of the DOE-2 one shown above. 

(sorry about the wierd formatting- I really don't understand how my Thunderbird mail server does these things...)

Joe
    

On 3/2/2017 9:17 AM, Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxm [EnergyPlus_Support] wrote:
 
Dear Chris,
Are you saying that you have manufacturer data and want to calculate the curve coefficients? If so, it wouldn't be hard to derive.

On the other hand, I don't think I've ever seen data which accounts for cycling losses, so I normally use curves from example files :), or make the result always = 1.0. (e.g., a quadratic curve's coefficients would be 1,0,0)

From the I/O Reference:
"The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling. This curve is typically a quadratic or cubic but any curve or table with one independent variables can be used."

On Thu, Mar 2, 2017 at 9:36 AM, Chris Jones cj@xxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@yahoogroups.com> wrote:
 

The EnergyPlus installation includes an excel spreadsheet for
calculating DX cooling curve coefficients. That spreadsheet includes
two curves - the cooling capacity curve based on indoor wetbulb and
outdoor air drybulb and the cooling EIR based on those temperatures.
Missing is the cooling EIR based on part load.

Is anyone aware of a spreadsheet that allows for calculation of this
third curve?

--

Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3
416-697-0056




--

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct / Mobile: 616.450.8653
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--

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct / Mobile: 616.450.8653
jim@buildingperformanceteam.com

Website l  LinkedIn

Coffee cup conversation: Our friends, our company, our culture, our country, ourselves are not renewed once and for all. They are renewed every day.




--

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l  LinkedIn

Coffee cup conversation: Our friends, our company, our culture, our country, ourselves are not renewed once and for all. They are renewed every day.



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Posted by: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>


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