[Equest-users] Chiller curve ball
Paul Diglio
paul.diglio at sbcglobal.net
Thu Mar 10 09:43:23 PST 2011
Pasha:
I question you comment that scroll compressors are way less efficient than screw
compressors. Can you explain what constitutes way less?
I looked up two air cooled Carrier chillers, both sized 140 tons.
The screw machine (30XA) has a full load EER of 10.6. The scroll (30RB) has a
full load EER of 9.7.
The screw machine has an IPLV EER of 14.3 and a COP of 4.2. The scroll has a
IPLV EER of 13.6 and a COP of 4.0.
Yes, the screw is slightly more efficient, but I can't see a 10-15% increase in
energy usage especially since the IPLV EERs are so close.
Can you give an example of the EERs you have used for screws v. scrolls?
Paul Diglio
________________________________
From: Pasha Korber-Gonzalez <pasha.pkconsulting at gmail.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>
Cc: "Sami, Vikram" <Vikram.Sami at perkinswill.com>;
"equest-users at lists.onebuilding.org" <equest-users at lists.onebuilding.org>
Sent: Thu, March 10, 2011 12:10:09 PM
Subject: Re: [Equest-users] Chiller curve ball
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
>Perkins+Will. Ideas + buildings that honor the broader goals of society
>
>Perkins+Will is carbon neutral.Learn more about our 2030 Challenge Estimating +
>Evaluationtool for fossil fuel free buildings
>
>
>This email and any files transmitted with it are confidential and intended
>solely for the addressee. If you are not the named addressee you should not
>disseminate, distribute, copy, or alter this email.
>
>_______________________________________________
>Equest-users mailing list
>http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
>To unsubscribe from this mailing list send a blank message to
>EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110310/42b9af45/attachment.htm>
More information about the Equest-users
mailing list