Hi everyone, How can I generate the coefficients for compressor performance curves (for a refrigerated warehouse model)?
Is there a tool that inputs manufacturer data and outputs the curve coefficients? such as the CurveFitTool.xlsm but generates Bicubic curves, because the CurveFitTool has only Cubic, Quadratic, and Bi-quadratic options.
Thank you.
I've discovered a convenient solution for this issue by utilizing manufacturer product selection tools. Certain manufacturers offer tools that allow you to input specific data conditions, helping you identify the suitable compressor. Additionally, these tools provide performance data in either tabular form or as bicubic polynomials. Currently, I make use of two free tools: Coolselector2 from DANFOSS (Fig.1) and BITZER Software from BITZER (Fig.2).
If you have access to performance tabular data, you can perform regression analysis using EXCEL, although it requires additional effort (Fig.3).
Fig.1 
Fig.2 
Fig.3 
Zakaria, were you able to generated the Bi-Cubic performance curves from inputs of temperature, cooling capacity, and power consumption, as presented in the CurveFitTool? I have used CoolSeclector2 before, but it does not provide the Bicubic performance curves as you mentioned. Though the Bitzer Software looks too. I will have to try it out, but are you able to share information on how you performed the regression analysis using the Excel spreadsheet in Figure 3?
Hi, @Adam Sustainable,
The CurveFitTool does not generate the bi-cubic curves, but I used Bitzer and CoolSelector2 to get that data. To generate the curve data on CoolSelector2, you can find it (after choosing the desired compressor) in the "Code numbers and technical information" tab => "Export polynomials...".
Regarding the Excel process, it does require some data processing. As shown in Fig. 3, I input the capacity/power (denoted as Y) and the corresponding SST and SDT values. Then I perform calculations for SST^2, SST^3, SDT^2, SDT^3, and so on. To perform the regression analysis in Excel:
Following these steps, Excel will automatically generate the bi-cubic curve coefficients.
Thanks a lot Zakaria! I think I understand what you did in figure 3 now. I just wanted to confirm that in the Open Studio Bicubic Curve inputs that x represents the evaporator temperature and y represents the condenser temperature? Because CoolSelector 2 and Bitzer display their performance curves slightly different. Bitzer for example y = c1 + c2to + c3tc + c4to^2 + c5totc + c6tc^2 + c7to^3 + c8tcto^2 + c9totc^2 + c10tc^3. Furthermore, do you know what units the inputs should be for the Power(W) and Capacity (BTU/hr) curves in Open Studio? I am running my model in IP units.
It seems you answered your own question (the CurveFitTool.xlsm that comes with E+). Are you asking about how to use this tool? Or are you looking for sources of manufacturer data that can be input into the CurveFitTool?
Thank you so much for your answer! I greatly appreciated it. The compressor performance curves are Bicubic curves and the CurveFitTool.xlsm file only has Cubic, Quadratic, and Bi-quadratic options. So how do I use it to calculate the coefficient of a Bicubic curves to use it for compressorspower and capacity performance curves? And since you ask, where can I find the manufacturer's data and how to use the tool? Thank you very much.
Asked: 2023-02-02 10:40:05 -0600
Seen: 280 times
Last updated: Jan 28
Clarifying: Refrigeration compressors (such as for a refrigerated warehouse) require curves which are very different. If you are thinking about curves for DX cooling coils, CurveFitTool should be great.
Yes that right, I want to generate compressors bi-cubic curves for a refrigerated warehouse model.
I may be able to assist. Please contact me at: jvdirkes2@protonmail.com for more discussion.
Do you know about the curve data set available in EnergyPlus? If not, look for RefrigerationCompressorCurves.idf in the DataSets folder.
Thank you for your comments. Yes, I have been using the RefrigerationCompressorCurves.idf file, I want to know how the process is done to generate such curves so I can explain it if anyone asks.