I have a feeling that an evaporative cooling object is not the best object for a setpoint manager, since the evaporative effect varies dramatically as the inlet humidity / wet bulb varies.
I have used the same evap cooling object in some models previously when modeling an M-cycle cooler. In those models, I used the evap object upstream of a mixing box and included it as a part of the OutdoorAirSystem:EquipmentList. I used a Fixed Dry Bulb economizer, but did not try to control the outlet temperature directly as you are doing.
Since your application does not sound like a “real world” system, I suspect that you’re doing research. An alternative approach would be to define a DX or chilled water pre-cooling coil with a setpoint manager. If you want to zero the energy, define COP = 10,000
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
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From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Tuesday, July 08, 2014 1:32 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Outdoor Air Evaporative Precooling
Hello. I'm attempting to model an hvac system with the outdoor air intake having temperatures a set number of degrees cooler than the weather file. My current strategy is using the EvaporativeCooler:Direct:ResearchSpecial object with the follow outdoor air setpoint manager. When I check the node temperatures at the inlet and outlet nodes of the cooler, there isn't a temperature difference. I can't figure out what I'm doing wrong. I'd appreciate it if anyone has any ideas. Here's the pertinent text from the idf:
!- =========== ALL OBJECTS IN CLASS: EVAPORATIVECOOLER:DIRECT:RESEARCHSPECIAL ===========
EvaporativeCooler:Direct:ResearchSpecial,
OS:EvaporativeCooler:Direct:ResearchSpecial, !- Name
Always On Discrete 1, !- Availability Schedule Name
1, !- Cooler Effectiveness
0, !- Recirculating Water Pump Power Consumption {W}
Node 6, !- Air Inlet Node Name
Node 38, !- Air Outlet Node Name
Node 38, !- Sensor Node Name
, !- Water Supply Storage Tank Name
0, !- Drift Loss Fraction
2; !- Blowdown Concentration Ratio
!- =========== ALL OBJECTS IN CLASS: SETPOINTMANAGER:FOLLOWOUTDOORAIRTEMPERATURE ===========
SetpointManager:FollowOutdoorAirTemperature,
Follow Outdoor Air Temperature, !- Name
Temperature, !- Control Variable
OutdoorAirDryBulb, !- Reference Temperature Type
-10, !- Offset Temperature Difference {deltaC}
80, !- Maximum Setpoint Temperature {C}
-5, !- Minimum Setpoint Temperature {C}
Node 38; !- Setpoint Node or NodeList Name
!- =========== ALL OBJECTS IN CLASS: OUTPUT:VARIABLE ===========
Output:Variable,
Node 38, !- Key Value
System Node Temperature, !- Variable Name
Hourly; !- Reporting Frequency
Output:Variable,
Node 6, !- Key Value
System Node Temperature, !- Variable Name
Hourly; !- Reporting Frequency
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Posted by: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
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