Hi Jim, If you are just looking for example curves, I might suggest reviewing the curve library for the DOE-2.2R (refrigeration) version; below is an excerpt from the help manual.  These curves are in IP units, but could be converted to SI.  Unfortunately, DOE-2 doesn't include a curve fit method for bi-cubic curves either.  A few years ago, I did some work to calibrate a DOE-2.2R model to an actual refrigerated warehouse project and was surprised by how close the modeled vs predicted was; though I did not have the time to do enough an in-depth review/comparison to strengthen my confidence in the many important model assumptions/algorithms. David On 9/18/2013 2:11 PM, Jim Dirkes wrote: ```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. The Building Performance Team James V. Dirkes II, P.E., BEMP , LEED AP 1631 Acacia Drive NW Grand Rapids, MI 49504 616 450 8653 ________________________________________ From: EnergyPlus_Support@xxxxxxxxxxxxxxx [EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Niraj Poudel [nirajpdl@xxxxxxxxx] 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 > wrote: 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 616 450 8653 ________________________________________ From: EnergyPlus_Support@xxxxxxxxxxxxxxx [EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of jeannieboef@xxxxxxxxx [jeannieboef@xxxxxxxxx] Sent: Wednesday, September 18, 2013 13:05 To: EnergyPlus_Support@xxxxxxxxxxxxxxx Cc: EnergyPlus_Support@xxxxxxxxxxxxxxx Subject: Re: [EnergyPlus_Support] Merging zones having FCUs (Merging FCUs) 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 Tel. +49 30 6706662-23 On 18.09.2013, at 17:32, Richard Raustad >> 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: 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 ``` ```-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 50 Years ------------------------------------ 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 -- 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! 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