Curve tab
There are two sets of curves for Air Cooled Chillers depending on the operating mode of the chiller: Cooling Mode and Ice Storage. The description of the curves are below.
Capacity Curve
This biquadratic curve shows the percentage of full cooling capacity as a function of the entering condenser fluid temperature and the leaving chilled water temperature. Inputs consists of two independent variables, six coefficients, and min and max values for each of the independent variables. The equation for the capacity curve is:
Where:
Z = Cooling Capacity
C1 to C6 = coefficients
X = Condenser temperature
Y = Chilled Water Temperature
The curve has the following fields:
X Axis: Entering Condenser fluid temperature (°F, °C).
Y Axis: Cooling Capacity (%).
Tchw,l Min / Max : Minimum and maximum temperature values (°F, °C) for the Chilled water leaving temperature variable. These values determine the three chilled water temperatures plotted, one is the maximum, one is the minimum and the last one is the midpoint between them.
Tcond,l Min / Max: Minimum and Maximum temperature values (°F, °C) for the Condenser Temperature variable.
Ambient Relief Curve
This biquadratic curve represents the chiller’s energy input to cooling output ratio as a function of the entering condenser fluid temperature and the leaving chilled water temperature.
Inputs consists of two independent variables, six coefficients, and min and max values for each of the independent variables. The equation for the capacity curve is:
Where:
Z = Chiller’s electric consumption (%)
C1 to C6 = coefficients
X = Condenser temperature
Y = Chilled Water Temperature
The curve has the following fields:
X Axis: Entering Condenser fluid temperature (°F, °C).
Y Axis: Chiller’s electric consumption (%)
Tchw,l Min / Max : Minimum and maximum temperature values (°F, °C) for the Chilled water leaving temperature variable. These values determine the three chilled water temperatures plotted, one is the maximum, one is the minimum and the last one is the midpoint between them.
Tcond,l Min / Max: Minimum and Maximum temperature values (°F, °C) for the Condenser Temperature variable.
Power Curve (Electric Input to Cooling Output Ratio Function of Part Load Ratio Curve)
This quadratic curve represents the chiller’s electric consumption at part load with operating temperatures at design values. This curve is generated by dividing the operating electric input power by the available full-load capacity at the specific operating temperatures. The curve output should decrease from 1 towards 0 as part-load ratio decreases from 1 to 0.
The equation for the Fuel Capacity Curve is:
Where:
y = Chiller’s electric consumption (%)
C1 to C3 = coefficients
X = Part Load
The curve has the following fields:
X Axis: Full Load (%)
Y Axis: Full power (%)
Curve Type: The curve can be selected as quadratic or cubic.
Load Min / Max: Minimum and Maximum Load percentage