Chiller:ConstantCOP
Used in:
- Chilled water loop, supply side
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Used in:
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This chiller model is based on a simple, constant COP simulation of the chiller. In this case, performance does not vary with chilled water temperature or condenser conditions. Such a model can be useful when detailed performance data is not available.
The auto-generated name of the chiller can be edited.
The type of chiller can be one of these options:
The Chiller type cannot be edited directly. To use a different type you must add a new chiller, selecting the appropriate type from the drop list.
This numeric field contains the nominal cooling capacity of the chiller (in W or Btu/h). Alternatively, this field can be autosized.
This numeric field contains the chiller’s coefficient of performance to be used for all operating conditions in the simulation. Unlike Chiller EIR, the CoP entered for Constant CoP chillers should include the energy consumed by the condenser fans for air and evaporatively cooled chillers.
This choice field determines how the chiller operates with respect to the intended fluid flow through the device’s evaporator. There are three choices for specifying operating modes for the intended flow behaviour:
In all cases the operation of the external plant system can also impact the flow through the chiller - for example if the relative sizes and operation are such that flow is restricted and the requests cannot be met.
For variable flow chilled water loops these options are available: 2-Leaving setpoint modulated and 3-Not modulated.
For constant flow chilled water loops these options are available: 1-Constant flow and 3-Not modulated.
The type of loop (variable/constant flow) can be changed by modifying the Plant loop flow type on the Chilled water plant loop dialog.
Note: When the 2-Leaving setpoint modulated option is selected then you must add an extra Setpoint manager immediately downstream of the chiller chilled water outlet to define the temperature of the water supplied.
The sizing factor is used when the chiller design inputs are autosized. In this case the autosizing results are multiplied by this additional sizing factor. The usual value to enter is 1.0.
The inputs that would be altered by the sizing factor are: Nominal capacity, Design chilled water flow rate and Design condenser water flow rate.
The most common use of the sizing factor is for sizing chillers to meet only part of the design load while continuing to use the autosizing feature. For example when a set of chillers is chained together to supply chilled water to a plant loop, this sizing factor can be used to indicate the proportion of the load to be met by each chiller.
See also the section on Autosizing HVAC Components
The condenser type determines what type of condenser will be included with this chiller. Valid condenser types are:
The default is 2-Water cooled which requires the full specification of the Condenser loop and its associated equipment. 1-Air cooled and 3-Evaporatively cooled do not require a Condenser loop to be specified.
For a variable flow chiller this is the maximum water flow rate and for a constant flow chiller this is the design water flow rate through the chiller’s evaporator. The units are (in m3/s or gal/min). This numeric input field must be greater than zero, or it can be autosized.
This numeric field contains the chiller’s operating condenser water flow rate (in m3/s or gal/min). This field can be autosized.
This field is not used Air cooled and Evaporatively cooled Condenser types.
This numeric field contains the capacity of the DX coil’s electric evaporative cooler basin heater in (W/K or Btu/h-F). This field only applies for Condenser type = Evaporatively cooled. This field is used in conjunction with the Basin Heater Setpoint Temperature described in the following field. The basin heater electric power is equal to this field multiplied by the difference between the basin heater set point temperature and the outdoor dry-bulb temperature. The basin heater only operates when the chiller is off, regardless of the basin heater schedule described below. The basin heater capacity must be greater than or equal to zero.
This numeric field contains the set point temperature (in ˚C or ˚F) for the basin heater described in the previous field. This field only applies for Condenser type = Evaporatively cooled. The basin heater is active when the outdoor air dry-bulb temperature falls below this setpoint temperature, as long as the chiller is off. This set point temperature must be greater than or equal to 2˚C.
This alpha field contains the name of the basin heater operating schedule. This field only applies for Condenser type = Evaporatively cooled. The basin heater operating schedule is assumed to be an on/off schedule and the heater is available to operate any time the schedule value is greater than 0. The basin heater operates when scheduled on and the outdoor air dry-bulb temperature is below the set point temperature described in the previous field. Regardless of this schedule, the basin heater can only operate when the chiller is off.
Many output variable names are common across all chiller types. These generic chiller output names all begin with the word "Chiller". Certain chiller types have additional output variables which are specific to that type of chiller. Specific chiller output names begin with the chiller type, for example, "Gas Absorption Chiller Heating Energy [J]." Chiller energy use is added to the appropriate plant-level meters as a cooling end-use.
HVAC,Average,Chiller Electric Power [W]
HVAC,Sum,Chiller Electric Consumption [J]
Zone,Meter,Electricity:Plant [J]
Zone,Meter,Cooling:Electricity [J]
HVAC,Average,Chiller Evap Heat Trans Rate [W]
HVAC,Sum,Chiller Evap Heat Trans [J]
Zone,Meter,EnergyTransfer:Plant [J]
Zone,Meter,Chillers:EnergyTransfer [J]
HVAC,Average,Chiller Evap Water Inlet Temp [C]
HVAC,Average,Chiller Evap Water Outlet Temp [C]
HVAC,Average,Chiller Evap Water Mass Flow Rate [kg/s]
HVAC,Average,Chiller Cond Heat Trans Rate [W]
HVAC,Sum,Chiller Cond Heat Trans [J]
Zone,Meter,HeatRejection:EnergyTransfer [J]
HVAC,Average,Chiller COP [W/W]
The following output is applicable only for air-cooled or evap-cooled chillers:
HVAC,Average,Chiller Cond Air Inlet Temp [C]
The following outputs are applicable only for evap-cooled chillers:
HVAC,Average,Chiller Basin Heater Electric Power [W]
HVAC,Average,Chiller Basin Heater Electric Consumption [J]
The following three outputs are only available for water-cooled chillers:
HVAC,Average,Chiller Cond Water Inlet Temp [C]
HVAC,Average,Chiller Cond Water Outlet Temp [C]
HVAC,Average,Chiller Cond Water Mass Flow Rate [kg/s]
HVAC,Average,Chiller Shaft Power [W]
These outputs are the electric power input to the chiller. In the case of steam or fuel-powered chillers, this repesents the internal chiller pumps and other electric power consumption. Consumption is metered on Cooling:Electricity, Electricity:Plant, and Electricity:Facility.
These outputs are the evaporator heat transfer which is the cooling delivered by the chiller. Chiller Evap Heat Trans is metered on Chillers:EnergyTransfer, EnergyTransfer:Plant, and EnergyTransfer:Facility.
These outputs are the evaporator (chilled water) inlet and outlet temperatures and flow rate.
This output is the coefficient of performance for the chiller during cooling operation. It is calculated as the evaporator heat transfer rate (Chiller Evap Heat Trans Rate) divided by the “fuel” consumption rate by the chiller. For the constant COP and electric chillers, the “fuel” is electricity so the divisor is Chiller Electric Power [W]. For the absorption chiller, the “fuel” is steam so the divisor is Steam Consumption Rate [W].
For the engine driven chiller and combustion turbine chiller, the output variable is renamed as Chiller Fuel COP to clarify that the primary energy input to the chiller is a gaseous or liquid fuel (natural gas, diesel, gasoline, etc.). The divisor is the appropriate fuel consumption rate (Chiller [fuel type] Consumption Rate).
For the direct fired absorption chiller, this variable is renamed as Direct Fired Absorption Chiller Cooling Fuel COP and the divisor is Direct Fired Absorption Chiller Cooling Gas Consumption Rate.
Note that this variable is reported as zero when the chiller is not operating. When reported for frequencies longer than "detailed" (such as timestep, hourly, daily, monthly or environment), this output will only be meaningful when the chiller is operating for the entire reporting period. To determine an average COP for a longer time period, compute the COP based on total evaporator heat transfer divided by total electric or fuel input over the desired period.
This output is the operating part-load ratio of the indirect absorption chiller. This output may fall below the minimum part-load ratio specified in the input. For this case, the Chiller Cycling Fraction is used to further define the performance of the indirect absorption chiller.
This output is the fraction of the timestep the indirect absorption chiller operates. When the chiller operates above the minimum part-load ratio, a chiller cycling fraction of 1 is reported. When the chiller operates below the minimum part-load ratio, the chiller cycling fraction reports the fraction of the timestep the indirect absorption chiller operates.
These outputs are the condenser heat transfer which is the heat rejected from the chiller to either a condenser water loop or through an air-cooled condenser. Chiller Cond Heat Trans is metered on HeatRejection:EnergyTransfer, EnergyTransfer:Plant, and EnergyTransfer:Facility.
This output is the condenser (heat rejection) inlet temperature for air-cooled or evap-cooled chillers. For an air-cooled chiller, this output would be the dry-bulb temperature of the air entering the condenser coil. For an evap-cooled chiller, this output would be the wet-bulb temperature of the air entering the evaporatively-cooled condenser coil.
These outputs are the electric power input to the chiller’s basin heater (for evaporativelycooled condenser type). Consumption is metered on Chillers:Electricity, Electricity:Plant, and Electricity:Facility
These outputs are the condenser (heat rejection) inlet and outlet temperatures and flow rate for water-cooled chillers.
For engine-driven and turbine-driven chillers, these outputs are the shaft power produced by the prime mover and transferred to the chiller compressor.
For chillers with heat recovery, such as engine-driven chillers, these outputs are the components of recoverable energy available. For a given chiller type, one or more of the following components may be applicable: Lube (engine lubricant), Jacket (engine coolant), Exhaust (engine exhaust), and Total. Chiller Lube Heat Recovery, Chiller Jacket Heat Recovery, and Chiller Exhaust Heat Recovery are metered on HeatRecovery:EnergyTransfer, EnergyTransfer:Plant, and EnergyTransfer:Facility.
This is the exhaust temperature leaving an engine chiller.
These outputs are the heat recovery inlet and outlet temperatures and flow rate for chillers with heat recovery such as engine-driven and gas turbine chillers.
These outputs are the steam or fuel input for steam or fuel-fired chillers. Valid fuel types depend on the type of chiller. <FuelType> may be one of: Gas (natural gas), Steam, Propane, Diesel, Gasoline, FuelOil#1, and FuelOil#2. Consumption is metered on Cooling:<FuelType>, <FuelType>:Plant, and <FuelType>:Facility.