[Equest-users] Chiller curve ball

[Pasha Korber-Gonzalez]

Aside from the curve input data--wouldn't you expect to see at least a
noticeable increase in chiller energy as Scroll chillers are WAY LESS
Efficient than Screw chillers anwyay?

Vik--if you are staring with a screw chiller profile and then are adjusting
to represent scroll compressor systems I think you would expect to see some
increase in chiller energy for your scroll compressors---and you probably
have multiple scroll compressors where typically the screw chiller profiles
are representing a single compressor unloading performance versus multiple
compressors unloading on one machine...

I agree that maybe 30% increase is out of whack, but my experience tells me
that a 10-15% increase in compressor energy would not be out of line for
scroll compressors and chillers versus screw chiller performance
capabilities.

I'm sorry I can't offer any help with the input of the curve data, my
experience with custom curves is less than ideal (or successful).  I have
found that my attempts at using custom chiller curves yields too much
questionability (& confusion on my end) and less than confident energy
results with each manipulation of the eQuest equipment performance curves
and variables.

Pasha

On Wed, Mar 9, 2011 at 6:19 PM, Paul Diglio <paul.diglio at sbcglobal.net>wrote:

>  Vikram:
>
> When defining a screw compressor in eQuest, I see three curves required.
>
> 1. EIR f(CHWT & ECT) which is the energy input ratio as a function of the
> evaporator leaving water temperature and the condenser water entering
> temperature.  This is called lift.  eQuest calls this DT.
>
> 2.Cap f(CHWT & ECT) which is the capacity as a function of lift.
>
> 3.EIR f(PLR & DT) which is the energy input ratio as a function of the part
> load ratio and the DT or chiller lift.
>
> Creating a  performance curve using the temperature difference between the
> condenser water entering and leaving temperature is incorrect.  I think you
> realize this because your chiller energy went up 30%.
>
> If you are modeling a constant chilled water supply temperature you can
> plug that in as Independent 1 and use the condenser entering water
> temperature as Independent 2.  If your chilled water temperature will be
> reset based on terminal load or outside air temperature, then you would need
> to get the chiller modeled by the manufacturer.
>
> Paul Diglio
>
>
>  ------------------------------
> *From:* "Sami, Vikram" <Vikram.Sami at perkinswill.com>
> *To:* "equest-users at lists.onebuilding.org" <
> equest-users at lists.onebuilding.org>
> *Sent:* Wed, March 9, 2011 6:54:13 PM
>
> *Subject:* [Equest-users] Chiller curve ball
>
>  Ok – so I’m probably doing this all wrong.
>
>
>
> I am trying to model a York scroll chiller in EQUEST. The table below
> illustrates the Part Load rating Data
>
>
>
> *Load % ** ***
>
> * **Capacity (Tons) ** *
>
> * **Cond. EWT (°F) ** *
>
> * **Cond. LWT (°F) ** *
>
> * **Compressor kW ** *
>
> *EER*
>
> *COP*
>
> *EIR*
>
> 100
>
> 135.8
>
> 85
>
> 95
>
> 104.1
>
> 15.6
>
> 4.6
>
> 0.217391
>
> 83.3
>
> 116.8
>
> 79.4
>
> 87.9
>
> 81
>
> 17.3
>
> 5.1
>
> 0.196078
>
> 66.7
>
> 96.9
>
> 73.5
>
> 80.4
>
> 60.1
>
> 19.3
>
> 5.7
>
> 0.175439
>
> 50
>
> 73.5
>
> 66.7
>
> 71.8
>
> 41.7
>
> 21.2
>
> 6.2
>
> 0.16129
>
> 33.3
>
> 48.2
>
> 65
>
> 68.4
>
> 26.6
>
> 21.7
>
> 6.4
>
> 0.15625
>
> 16.7
>
> 23.6
>
> 65
>
> 66.6
>
> 13.1
>
> 21.7
>
> 6.4
>
> 0.15625
>
>
>
> eQUEST doesn’t seem to have a scroll chiller option – I assume screw is the
> closest thing to it.
>
>
>
> As far as I can tell – you need to define 3 performance curves:
>
> 1.       A curve that defines the EIR based on the condenser water temp
>
> "York - Temp vs EIR" = CURVE-FIT
>
>    TYPE             = BI-QUADRATIC-T
>
>    INPUT-TYPE       = DATA
>
>    INDEPENDENT-1    = ( 85, 79.4, 73.5, 66.7, 65, 65 )
>
>    INDEPENDENT-2    = ( 95, 87.9, 80.4, 71.8, 68.4, 66 )
>
>    DEPENDENT        = ( 0.217391, 0.196, 0.175, 0.161, 0.156, 0.156 )
>
>    ..
>
> 2.       A curve that defines the part load based on the condenser water
> temp
>
> "York Temp vs Part Load" = CURVE-FIT
>
>    TYPE             = BI-QUADRATIC-T
>
>    INPUT-TYPE       = DATA
>
>    INDEPENDENT-1    = ( 85, 79.4, 73.5, 66.7, 65, 65 )
>
>    INDEPENDENT-2    = ( 95, 87.9, 80.4, 71.8, 68.4, 66 )
>
>    DEPENDENT        = ( 1, 0.833, 0.667, 0.5, 0.333, 0.167 )
>
>    ..
>
> 3.       A curve that  defines the EIR based on the part load.
>
> "York Part Load vs EIR" = CURVE-FIT
>
>    TYPE             = QUADRATIC
>
>    INPUT-TYPE       = DATA
>
>    INDEPENDENT      = ( 1, 0.833, 0.667, 0.5, 0.333, 0.167 )
>
>    DEPENDENT        = ( 0.217, 0.196, 0.175, 0.161, 0.156, 0.156 )
>
>    ..
>
>
>
>
>
> When I apply these curves to my chiller, my cooling energy goes up by 30%.
> Seems like a lot.      Is this reasonable or am I doing something wrong with
> my curve selection?
>
>
>
> Muchas Gracias in advance
>
> *We've moved!  Please note our new address. ***
>
> *Vikram Sami*, LEED AP BD+C
>
> Sustainable Design Analyst
>
> 1315 Peachtree St. NE, Atlanta, GA 30309
>
> t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com
> www.perkinswill.com
>
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