Performance curves

The behaviour of heating and cooling units varies depending on the operating conditions. CYPETHERM energy simulation programs using the EnergyPlus™ calculation engine can consider this variation in two ways:

• By selecting the default performance curves included for each unit. To do this, the “Default” option is selected when editing the performance curves of the unit.
• By editing the performance curves of the hydronic production units (boilers and chillers). To do this, the ‘User-defined’ option is selected when editing the performance curves of the unit. There are two options for entering this data in the program: in the form of a table or in the form of a polynomial curve.

User-defined performance curves for chillers

Rated conditions

Rated conditions are the operating conditions under which the rated characteristics of the units are defined.

The performance curves must be defined in such a way that under rated conditions their value is equal to 1.

All performance curves for the same units must be defined for the same rated conditions.

• Water temperature at chiller outlet
• Fluid temperature at condenser inlet

CapFT curve

Cooling power correction coefficient.

EIRFT curve

Electricity consumption correction factor.

Note:

In the CapFT and EIRFT curves, the "x" and "y" values refer to the following parameters:
x: Water temperature at chiller outlet (°C)
y: Fluid temperature at condenser inlet (°C)

Depending on the option selected in "Condenser type", the temperature of the fluid at the inlet of the condenser is referred to:
- Water cooled: Water temperature.
- Air cooled: Air dry bulb temperature.
- Evaporative cooling: Air wet bulb temperature.

EIRFPLR curve

Electricity consumption correction factor.

Note:

In the EIRFPLR curve, the "x" value refers to the following parameter:
- x: Part-load ratio (PLR)

User-defined performance curves for boilers

Rated conditions

Rated conditions are the operating conditions under which the rated characteristics of the units are defined.

The performance curves must be defined in such a way that under rated conditions their value is equal to 1.

All performance curves for the same units must be defined for the same rated conditions.

• Water temperature (At the inlet of the boiler / At the outlet of the boiler)
• Part-load ratio (PLR)
  Equal to 1.

EffFPLRT curve

Efficiency correction factor.

Note:

In the EffFPLRT curve, the "x" and "y" values refer to the following parameters:
- x: Part-load ratio (PLR)
- y: Water temperature (°C)