The EnergyPlus Curve Fit spreadsheet Tool can be used to generate HVAC performance curves in EnergyPlus curve object format. For each set of performance data entered, Capacity and EIR performance curves are generated, and these curves are generated either as a function of temperature(s) or flow fraction. The Capacity and EIR of Cooling DX Coils as a function of temperatures require only Biquadratic curve whereas Capacity and EIR of Heating DX Coils may use Biquadratic, Cubic and Quadratic curves. The selection of either of these curves is dependent on availability of performance data. The Capacity and EIR as a function of flow fraction allows either Cubic or Quadratic curve type.
The curve coefficients calculated by the tool can be copied over manually into the relevant DesignBuilder dialogs.
Note: The curve fit spreadsheet can typically be found in a folder like C:\EnergyPlusV8-8-0\PreProcess\HVACCurveFitTool after installing EnergyPlus.
The curve types allowed are:
Cooling Capacity as a Function of Temperatures: Biquadratic Curve
cCapacity = a0 + a1*X + a2*X^2 + a3*Y + a4*Y^2 + a5*X*Y
Heating Capacity as a Function of Temperatures: Biquadratic curve
hCapacity = a0 + a1*X + a2*X^2 + a3*Y + a4*Y^2 + a5*X*Y
Heating Capacity as a Function of Temperatures: Cubic Curve
hCapacity = a0 + a1*X + a2*X^2 + a3*x^3
Energy Input Ratio (EIR) as a Function of Temperatures: Biquadratic Curve
EIR = a0 + a1*X + a2*X^2 + a3*Y + a4*Y^2 + a5*X*Y
Energy Input Ratio (EIR) as a Function of Temperatures: Cubic Curve
EIR = a0 + a1*X + a2*X^2 + a3*x^3
Capacity as a Function of Flow Fraction: Cubic Curve
EIR = a0 + a1*X + a2*X^2 + a3*x^3
Capacity as a Function of Flow Fraction: Quadratic Curve
EIR = a0 + a1*X + a2*X^2
Energy Input Ratio (EIR) as a Function of Flow Fraction: Cubic Curve
EIR = a0 + a1*X + a2*X^2 + a3*x^3
Energy Input Ratio (EIR) as a Function of Flow Fraction: Quadratic Curve
EIR = a0 + a1*X + a2*X^2
These performance curves as a function of temperatures are generated for a given set of input data at a given speed. The curves as a function of flow fraction are generated at the rated temperature conditions. The rated test condition is the AHRI standard rated test condition. The AHRI standard test condition may vary by the equipment type. For multiple speeds or multiple stage DX Coils, different curve sets can be generated by entering a different set of data for each speed or stage at a time. This tool can generate the following four curve types: (1) Capacity as a function of temperatures, (2) Capacity as a function of flow fraction, (3) EIR as a function of temperatures, and (4) EIR as a function of flow fraction. The tool automatically populates the labels for each data inputs variable when users select the Coil Type, Independent Variables, Curve Type, and Units as shown on INPU tab. The labels shown in the INPU tab are selected for DX Coil to generate capacity and EIR biquadratic curves as function of temperatures. The tool can be used for the DX coil types: Coil:Cooing:DX:SingleSpeed, Coil:Heating:DX:SingleSpeed, Coil:Cooing:DX:TwoSpeed (high and low speed) , CoilPerformance:DX:Cooling (each stage), and any HVAC equipment that use Biquadratic, Cubic or Quadratic curves. To add this flexibility generic input data labels can be populated by selecting "Other" for DX Coil Type input field, located in Cell B3 in the INPUT tab.