COOLINGTOWER:SINGLESPEED
This tower model is based on Merkel's theory, which is also the basis for the tower model in ASHRAE's HVAC1 Toolkit. The open wet cooling tower is modeled as a counter flow heat exchanger with a single-speed fan drawing air through the tower (induced-draft configuration). Added fluid bypass as an additional capacity control. 8/2008. For a multi-cell tower, the capacity and air/water flow rate inputs are for the entire tower.
Name
Type: alphanumeric
Tower Name
Water Inlet Node Name
Type: node
Name of tower water inlet node
Water Outlet Node Name
Type: node
Name of tower water outlet node
Design Water Flow Rate
Type: real number
Leave field blank if tower performance input method is NominalCapacity
Unit: m3/s
Design Air Flow Rate
Type: real number
Unit: m3/s
Design Fan Power
Type: real number
This is the fan motor electric input power
Unit: W
Design U-Factor Times Area Value
Type: real number
Leave field blank if tower performance input method is NominalCapacity
Unit: W/K
Maximum: 2100000.0
Free Convection Regime Air Flow Rate
Type: real number
Unit: m3/s
Minimum: 0.0
Default: 0.0
Free Convection Regime Air Flow Rate Sizing Factor
Type: real number
This field is only used if the previous field is set to autocalculate.
Default: 0.1
Free Convection Regime U-Factor Times Area Value
Type: real number
Unit: W/K
Minimum: 0.0
Maximum: 300000.0
Default: 0.0
Free Convection U-Factor Times Area Value Sizing Factor
Type: real number
This field is only used if the previous field is set to autocalculate and the Performance Input Method is UFactorTimesAreaAndDesignWaterFlowRate
Default: 0.1
Performance Input Method
Type: choice
(UFactorTimesAreaAndDesignWaterFlowRate or NominalCapacity)
User can define tower thermal performance by specifying the tower UA, the Design Air Flow Rate and the Design Water Flow Rate, or by specifying the tower nominal capacity
Default: UFactorTimesAreaAndDesignWaterFlowRate
Heat Rejection Capacity and Nominal Capacity Sizing Ratio
Type: real number
Default: 1.25
Nominal Capacity
Type: real number
Nominal tower capacity with entering water at 35C (95F), leaving water at 29.44C (85F), entering air at 25.56C (78F) wet-bulb temperature and 35C (95F) dry-bulb temperature. Design water flow rate assumed to be 5.382E-8 m3/s per watt (3 gpm/ton). Nominal tower capacity times (1.25) gives the actual tower heat rejection at these operating conditions.
Unit: W
Free Convection Capacity
Type: real number
Tower capacity in free convection regime with entering water at 35C (95F), leaving water at 29.44C (85F), entering air at 25.56C (78F) wet-bulb temperature and 35C (95F) dry-bulb temperature. Design water flow rate assumed to be 5.382E-8 m3/s per watt of nominal tower capacity (3 gpm/ton). Tower free convection capacity times (1.25) gives the actual tower heat rejection at these operating conditions.
Unit: W
Minimum: 0.0
Free Convection Nominal Capacity Sizing Factor
Type: real number
This field is only used if the previous field is set to autocalculate
Default: 0.1
Design Inlet Air Dry-Bulb Temperature
Type: real number
Enter the tower's design inlet air dry-bulb temperature
Unit: C
Minimum: 20.0
Default: 35.0
Design Inlet Air Wet-Bulb Temperature
Type: real number
Enter the tower's design inlet air wet-bulb temperature
Unit: C
Minimum: 20.0
Default: 25.6
Design Approach Temperature
Type: real number
Enter the approach temperature corresponding to the design inlet air wet-bulb temperature and design range temperature. Design approach temp = outlet water temperature minus inlet air wet-bulb temperature at design conditions. Autosized to 3.9 deltaC.
Unit: deltaC
Default: autosize
Design Range Temperature
Type: real number
Enter the range temperature corresponding to the design inlet air wet-bulb temperature and design approach temperature. Design range = inlet water temperature minus outlet water temperature at design conditions. Autosized to 5.5 deltaC.
Unit: deltaC
Default: autosize
Basin Heater Capacity
Type: real number
This heater maintains the basin water temperature at the basin heater setpoint temperature when the outdoor air temperature falls below the setpoint temperature. The basin heater only operates when water is not flowing through the tower.
Unit: W/K
Minimum: 0.0
Default: 0.0
Basin Heater Setpoint Temperature
Type: real number
Enter the outdoor dry-bulb temperature when the basin heater turns on
Unit: C
Minimum: 2.0
Default: 2.0
Basin Heater Operating Schedule Name
Type: list of objects
(
SCHEDULE:FILE,
EXTERNALINTERFACE:SCHEDULE,
SCHEDULE:YEAR,
EXTERNALINTERFACE:FUNCTIONALMOCKUPUNITIMPORT:TO:SCHEDULE,
SCHEDULE:CONSTANT or
SCHEDULE:COMPACT)
Schedule values greater than 0 allow the basin heater to operate whenever the outdoor air dry-bulb temperature is below the basin heater setpoint temperature. If a schedule name is not entered, the basin heater is allowed to operate throughout the entire simulation.
Evaporation Loss Mode
Type: choice
(LossFactor or SaturatedExit)
Evaporation Loss Factor
Type: real number
Rate of water evaporation from the cooling tower and lost to the outdoor air [%/K] Evaporation loss is calculated as percentage of the circulating condenser water rate Value entered here is percent-per-degree K of temperature drop in the condenser water Typical values are from 0.15 to 0.27 [%/K].
Unit: percent/K
Default: 0.2
Drift Loss Percent
Type: real number
Rate of drift loss as a percentage of circulating condenser water flow rate Typical values are between 0.002 and 0.2% The default value is 0.008%
Unit: percent
Default: 0.008
Blowdown Calculation Mode
Type: choice
(ConcentrationRatio or ScheduledRate)
Blowdown Concentration Ratio
Type: real number
Characterizes the rate of blowdown in the cooling tower. Blowdown is water intentionally drained from the tower in order to offset the build up of solids in the water that would otherwise occur because of evaporation. Ratio of solids in the blowdown water to solids in the make up water. Typical values for tower operation are 3 to 5. The default value is 3.
Minimum: 2.0
Default: 3.0
Blowdown Makeup Water Usage Schedule Name
Type: list of objects
(
SCHEDULE:FILE,
EXTERNALINTERFACE:SCHEDULE,
SCHEDULE:YEAR,
EXTERNALINTERFACE:FUNCTIONALMOCKUPUNITIMPORT:TO:SCHEDULE,
SCHEDULE:CONSTANT or
SCHEDULE:COMPACT)
Makeup water usage due to blowdown results from occasionally draining a small amount of water in the tower basin to purge scale or other contaminants to reduce their concentration in order to maintain an acceptable level of water quality. Schedule values should reflect water usage in m3/s.
Supply Water Storage Tank Name
Type: list of objects
( or
WATERUSE:STORAGE)
Outdoor Air Inlet Node Name
Type: node
Enter the name of an outdoor air node
Capacity Control
Type: choice
(FanCycling or FluidBypass)
Default: FanCycling
Number of Cells
Type: integer
Minimum: 1
Default: 1
Cell Control
Type: choice
(MinimalCell or MaximalCell)
Default: MinimalCell
Cell Minimum Water Flow Rate Fraction
Type: real number
The allowable minimal fraction of the nominal flow rate per cell
Maximum: 1.0
Default: 0.33
Cell Maximum Water Flow Rate Fraction
Type: real number
The allowable maximal fraction of the nominal flow rate per cell
Minimum: 1
Default: 2.5
Sizing Factor
Type: real number
Multiplies the autosized capacity and flow rates
Default: 1.0
End-Use Subcategory
Type: alphanumeric
Any text may be used here to categorize the end-uses in the ABUPS End Uses by Subcategory table.
Default: General