Thanks, Niraj!
I want to predict Capacity and EIR for these compressors using Saturated Suction Temperature and Saturated Discharge Temperature as inputs. Those two variables apparently interplay in a bi-cubic form. Bi-cubic curves use 10 (!) coefficients that are combinations of the two (e.g., X, X^2, X^3, Y, Y^2, .... X*Y^2, Y*X^2, etc.)
I have been using the Excel LINEST function for all curves including linear, quadratic, cubic and bi-quadratic - and it works wonderfully for those. Not so for bi-cubic... That's my problem; I have a nice solution for other curve types that isn't working for bi-cubic curves. It could be a limitation of the LINEST function.... but I'm not sure.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Niraj Poudel [nirajpdl@xxxxxxxxx]
The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
________________________________________
Sent: Wednesday, September 18, 2013 16:24
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Deriving Bi-Cubic performance curves
Jim,
are you trying to explain some dependent values (say, y) with tabular data of the different independent values (say, x and z)? If so you might want to perform a regression analysis to come up with a curve (model) that explains the dependent variable. I am not familiar with compression objects performance curves, so if I am missing something please do ignore my message.
Niraj
On Wed, Sep 18, 2013 at 3:19 PM, Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx<mailto:jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>> wrote:616 450 8653<tel:616%20450%208653>
Dear forum,
I am involved with a modeling project for a refrigerated warehouse. The compressor object expects a bi-cubic performance curve, so I am busy making an Excel template in which to place tabular data and derive curve coefficients. I've never used b-cubic curves before, but it appears that my normal method of curve derivation in Excel does not work for these curve types. Since I'm no expert on this topic, it is very likely that I'm missing something! Have any of you derived bi-cubic curves? Are you willing to share some insights?
The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
________________________________________
From: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx> [EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>] On Behalf Of jeannieboef@xxxxxxxxx<mailto:jeannieboef@xxxxxxxxx> [jeannieboef@xxxxxxxxx<mailto:jeannieboef@xxxxxxxxx>]
Sent: Wednesday, September 18, 2013 13:05To: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>
Cc: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>
Subject: Re: [EnergyPlus_Support] Merging zones having FCUs (Merging FCUs)Tel. +49 30 6706662-23<tel:%2B49%2030%206706662-23>
Or work backwards... Total real FCU Rated powers = Total Rated FCU Volume Flow * Pressure Equivalent / (flow weighted average efficiency)
...just not sure if the efficiency should be flow or power weighted.
Mit freundlichen Grüßen- Sent from my iPhone (excuse the brevity)
i. A.
Jean Marais
b.i.g. bechtold
> http://energyplus.helpserve.com or send a message to <mailto:energyplus-support@xxxxxxxx<mailto:energyplus-support@xxxxxxxx>> energyplus-support@xxxxxxxx<mailto:energyplus-support@xxxxxxxx><mailto:energyplus-support@xxxxxxxx<mailto:energyplus-support@xxxxxxxx>>
On 18.09.2013, at 17:32, Richard Raustad <RRaustad@xxxxxxxxxxxx<mailto:RRaustad@xxxxxxxxxxxx><mailto:RRaustad@xxxxxxxxxxxx<mailto:RRaustad@xxxxxxxxxxxx>>> wrote:
Obviously there is a flaw in the DB approach. Try averaging the fan
pressure rise instead.
Fan:ConstantVolume,
75.0, !- Pressure Rise {Pa}
On 9/18/2013 6:38 AM, hisham.rashrash wrote:
> Hi,
> For one case, I tried to merge actual zones into larger thermal zones. Now, I have to model FCUs, using TemplateHVAC:Zone:FanCoil objects, in such a way that I put one FCU in each zone that must represent 4, 5 or even 11 real FCUs for example. I used the following approach:
> 1. I used the formula from DesignBuilder website (http://www.designbuilder.co.uk/programhelp/fans.htm) to find Fan Delta Pressure:
> Delta P = 1000 * SFP * Fan total efficiency (SFP: Specific Fan Power [W/(L/s)]
> I calculated each real FCU's Fan Delta P and added them up to find the equivalent FCU's fan Delta P.
> For example:
> I have 4 FCU's one for each of 4 guest rooms that I merged into one large room for simplification, the actual HVAC schedules give the following:
>
> FCU No. Power [kW] Air Flow [L/s]
> ==================================================
> 1 0.3 160
> 2 0.3 145
> 3 0.3 145
> 4 0.3 145
>
>
> Eqv. Delta P= 1000*(300[W]/160[L/s]+3*300[W]/145[L/s])*0.7=5657.33[Pa]
>
>
> 2. I found the equivalent FCU's airflow rate by adding the real FCUs' flow rates:
> Eqv. Flow Rate=160+3*145=595[L/s]
>
>
> I used the above values in the HVACTemplate:Zone:FanCoil object for the corresponding zone. The results were that the equivalent FCU's power calculated is 5 times larger (about 6[kW]) than actual component-FCUs' power when added up:
> >From table above: 0.3[kW/FCU]*4[FCUs]=1.2[kW]<6[kW]
>
>
> Please advise.
>
>
> Thank you very much.
>
>
> Regards,
> Hisham
>
>
>
>
> ------------------------------------
>
> Primary EnergyPlus support is found at:
>Phone: (321) 638-1454<tel:%28321%29%20638-1454>
> The primary EnergyPlus web site is found at:
> <http://www.energyplus.gov> http://www.energyplus.gov
>
> The group web site is:
> <http://groups.yahoo.com/group/EnergyPlus_Support/> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
>
> EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
> Yahoo! Groups Links
>
>
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Fax: (321) 638-1439<tel:%28321%29%20638-1439> or 1010
Visit our web site at: <http://www.fsec.ucf.edu> http://www.fsec.ucf.eduhttp://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx<mailto:energyplus-support@xxxxxxxx>
UCF - From Promise to Prominence: Celebrating 50 Years
------------------------------------
Primary EnergyPlus support is found at:
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links
--
Niraj Poudel, Architectural Engineer.
PhD student, PDBE Program.
Clemson University, Clemson, SC.
Linkedin: http://www.linkedin.com/pub/niraj-poudel/19/1ba/568
------------------------------------
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/EnergyPlus_Support/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/EnergyPlus_Support/join
(Yahoo! ID required)
<*> To change settings via email:
EnergyPlus_Support-digest@xxxxxxxxxxxxxxx
EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx
<*> To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
<*> Your use of Yahoo! Groups is subject to:
http://info.yahoo.com/legal/us/yahoo/utos/terms/