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What information should I input further for CoolingTower:TwoSpeed?

asked 2018-02-01 21:25:09 -0500

katsuya.obara gravatar image

I am having error below when I try to run the simulation with CoolingTower:TwoSpeed specifying NominalCapacity for Performance Input Method. I input Nominal capacity ,Fan Power, for Low,High Fan Speed. What information do I need to input further to make this calculation work?

   ** Severe  ** CoolingTower:TwoSpeed "COOLING TOWER TWO SPEED 3". Nominal capacity input method has been specified and tower UA at low fan speed is being autosized.
   **   ~~~   ** Tower UA at low fan speed will be set according to nominal tower capacity.
   ** Severe  ** Bad starting values for UA
   **  Fatal  ** Autosizing of cooling tower UA failed for tower COOLING TOWER TWO SPEED

idf file

CoolingTower:TwoSpeed,
    Cooling Tower Two Speed 3,  !- Name
    Node 289,                !- Water Inlet Node Name
    Node 290,                !- Water Outlet Node Name
    Autosize,                !- Design Water Flow Rate {m3/s}
    Autosize,                !- High Fan Speed Air Flow Rate {m3/s}
    30000,                   !- High Fan Speed Fan Power {W}
    Autosize,                !- High Fan Speed U-Factor Times Area Value {W/K}
    Autocalculate,           !- Low Fan Speed Air Flow Rate {m3/s}
    0.5,                     !- Low Fan Speed Air Flow Rate Sizing Factor
    15000,                   !- Low Fan Speed Fan Power {W}
    0.16,                    !- Low Fan Speed Fan Power Sizing Factor
    Autocalculate,           !- Low Fan Speed U-Factor Times Area Value {W/K}
    0.6,                     !- Low Fan Speed U-Factor Times Area Sizing Factor
    0,                       !- Free Convection Regime Air Flow Rate {m3/s}
    0.1,                     !- Free Convection Regime Air Flow Rate Sizing Factor
    0,                       !- Free Convection Regime U-Factor Times Area Value {W/K}
    0.1,                     !- Free Convection U-Factor Times Area Value Sizing Factor
    NominalCapacity,         !- Performance Input Method
    1.25,                    !- Heat Rejection Capacity and Nominal Capacity Sizing Ratio
    3661000,                 !- High Speed Nominal Capacity {W}
    1359000,                 !- Low Speed Nominal Capacity {W}
    0.5,                     !- Low Speed Nominal Capacity Sizing Factor
    ,                        !- Free Convection Nominal Capacity {W}
    0.1,                     !- Free Convection Nominal Capacity Sizing Factor
    25.6,                    !- Design Inlet Air Dry-Bulb Temperature {C}
    25.6,                    !- Design Inlet Air Wet-Bulb Temperature {C}
    Autosize,                !- Design Approach Temperature {deltaC}
    Autosize,                !- Design Range Temperature {deltaC}
    0,                       !- Basin Heater Capacity {W/K}
    2,                       !- Basin Heater Setpoint Temperature {C}
    ,                        !- Basin Heater Operating Schedule Name
    ,                        !- Evaporation Loss Mode
    0.2,                     !- Evaporation Loss Factor {percent/K}
    0.008,                   !- Drift Loss Percent {percent}
    ,                        !- Blowdown Calculation Mode
    3,                       !- Blowdown Concentration Ratio
    ,                        !- Blowdown Makeup Water Usage Schedule Name
    ,                        !- Supply Water Storage Tank Name
    ,                        !- Outdoor Air Inlet Node Name
    1,                       !- Number of Cells
    MinimalCell,             !- Cell Control
    0.33,                    !- Cell Minimum  Water Flow Rate Fraction
    2.5,                     !- Cell Maximum Water Flow Rate Fraction
    1,                       !- Sizing Factor
    General;                 !- End-Use Subcategory
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answered 2018-05-01 13:41:58 -0500

rkbest gravatar image

updated 2018-05-01 13:57:51 -0500

If you refer to the EnergyPlus I/O Reference for this section, you will find this

If the method “NominalCapacity” is selected then the fields “Design Water Flow Rate”, “U-Factor Times Area Value at Design Air Flow Rate” and “U-Factor Times Area Value at Free Convection Air Flow Rate” must be left blank, but the fields “Nominal Capacity” and “Free Convection Capacity” must be entered as described below.

You will need to calculate the 'Free convection capacity' as detailed here link text

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Asked: 2018-02-01 21:25:09 -0500

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Last updated: May 01 '18