Product tab
Design WB Effectiveness
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Default: 90%
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Typical Range: 50 to 80%
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Min/Max: 0 to 100%
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Units: N/A
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This field specifies the design effectiveness that is applied to the wet bulb depression to determine the conditions leaving the cooler. This effectiveness is a complicated function of the efficiency with which heat and mass are transferred on the tower side and the efficiency of heat exchange between the tower and airside flows. The model assumes that the effectiveness a function of flow fraction. The flow fraction is the ratio of the sum of tower and airside current flow rates and the sum of the tower and airside design flow rates.
Enable DB Eff. Modifier
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Default: No
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Typical Range: N/A
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Min/Max: N/A
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Units: N/A
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This field enables the design dry bulb effectiveness input to vary effectiveness of the evaporative cooler. It also enables the Drybulb Effectiveness Modifier Curve.
Design DB Effectiveness
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Default: 90%
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Typical Range: 50 to 80%
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Min/Max: 0 to 100%
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Units: N/A
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This input is the nominal design dry bulb effectiveness with respect to dry bulb temperature difference, i.e., dry operation and at design air flow rates, and no water evaporation or spraying on the tower.
Recirculating Pump
Full Load Energy Rate
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Default: 30 W
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Typical Range: 0 to 50 W
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Min/Max: 0 to 999,999
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Units: W, hp, kW, therms, W/(m3/sec), W/gpm, W/(L/sec)
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This numeric input field is the recirculating and spray pump electric power for the water sprayed on the coil.
Secondary Fan
Full Load Energy Rate
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Default: Auto Size or 0.00022 kW/(cfm), 46.61W/(m3/sec)
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Typical Range: 0 to 100
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Min/Max: 0 to 999,999
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Units: W/(cfm), W/(L/sec), W/(L/sec)-in H2O, kW/(cfm), kW/(L/sec), kW/(cfm)-in H2O, kW/(L/sec)-in H2O, W/(cfm)-in H2O, W/(m3/sec), BHP, W, kW
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Enter the full load energy value and select the corresponding units to describe the amount of energy consumed by the secondary fan at design airflow.
Secondary Airflow Rate
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Default: 100% Primary AIrflow
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Typical Range: 50 to 100%
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Min/Max: 0 to 100%
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Units: % Primary Airflow
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This field specifies the secondary airflow that will be flowing over the wetted heat exchanger tubes. This field is typically similar in magnitude to the primary airflow. This field can be autosized; if autosized, the program will determine if this loop is on the main air loop or an outdoor air path. If on the main air loop, the default value will be 100% of primary airflow. If on the outdoor air path, the flowrate is set to the larger of either the design minimum outdoor air intake or 50% of the main air loop design flow rate.
Evaporative Loss and Blowdown
Dewpoint Effectiveness
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Default: 90%
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Typical Range: 50 to 80%
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Min/Max: 0 to 100%
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Units: N/A
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This field specifies an effectiveness that is applied to the dew point depression to determine a bound for the conditions leaving the cooler. The model uses the warmer of the two temperatures determined from wet bulb depression.
Blowdown Concentration Ratio
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Default: 3
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Typical Range: 3 to 5
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Min/Max: 3 to 5
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Units: N/A
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This input field can be used to model additional water consumed by the cooler from blowdown. Blowdown is water that is intentionally drained from the coolers sump to offset the buildup of solids in the water that would otherwise occur because of evaporation. It can be characterized as the ratio of solids in the blowdown water to solids in the make-up water and is dimensionless.
Drift Loss
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Default: 0%
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Typical Range: 0 to 3%
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Min/Max: 0 to 100
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Units: %
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This input field can be used to model additional water consumed by the cooler from drift. Drift is water that leaves the cooling media as droplets and does not evaporate into the process air stream. For example, water may get blown off the evaporative media by winds and escape the air system. The value entered here is a simple fraction of the water consumed by the cooler for normal process evaporation. The amount of drift is this fraction times the water evaporated for the normal cooling process.
Operational Limits
Min Dry Bulb Limit
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Default: Low Limit
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Typical Range: Low Limit and 60 to 70°F, (High Limit and 16 to- 21°C)
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Min/Max: -999,999 to 999,999
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Units: W/(cfm), W/(L/sec), W/(L/sec)-in H2O, kW/(cfm), kW/(L/sec), kW/(cfm)-in H2O, kW/(L/sec)-in H2O, W/(cfm)-in H2O, W/(m3/sec), BHP, W, kW
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This input field defines the evaporative cooler inlet node dry bulb temperature minimum limit. The evaporative cooler will be turned off when evaporator cooler air inlet dry-bulb temperature falls below this value.
Operational Limits
Max Dry Bulb (DB) Limit
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Default: None
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Typical Range: High Limit and 82 to 100°F, High Limit and 28 to 35°C
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Min/Max: -999,999 to 999,999
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Units: °F; °C
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This input field defines the evaporative cooler air inlet dry bulb temperature maximum limits. The evaporative cooler will be turned off when the evaporative cooler air inlet node dry bulb temperature exceeds this value. Typical ranges when high limit is used is between 82 - 100 F (or 28 – 35 C).
Max Wet Bulb Limit
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Default: None
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Typical Range: Low Limit and 75 to 82°F, High Limit and 24 to 28°C
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Min/Max: -999,999 to 999,999
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Units: °F; °C
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This input field defines the evaporative cooler air inlet node air wetbulb temperature maximum limits. When the evaporative cooler air inlet node air wetbulb temperature exceeds this limit, then the evaporative cooler is turns off. Typical ranges when high limit is used is between 75 - 82 F (or 24 – 28 C).