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Energy Plus modelling HVAC without dehumidification

asked 2017-05-19 01:50:45 -0600

hullaballoo gravatar image

updated 2017-11-28 08:00:30 -0600

I'm trying to model a very simple air conditioning device in EnergyPlus, I don't have anything specific about the system yet, apart the fact that it is just a cooling device. I use: HVACTemplate:Zone:IdealLoadsAirSystem the cooling works just fine but when I look at the relative humidity it looks like the humidity stays constantly at 45%.

The climate is very hot and humid, therefore if the air is just cooled the relative humidity should rise, right? I put the Dehumidification Control Type to None so I am wondering why the relative humidity is so low. Perhaps I overlooked something. Can anybody help me with this?

Here are my settings:

HVACTemplate:Zone:IdealLoadsAirSystem,
  Thermal Zone 1   !- Zone Name
  thermostat,              !- Template Thermostat Name
  Assembly HVAC,           !- System Availability Schedule Name
  50,                      !- Maximum Heating Supply Air Temperature {C}
  13,                      !- Minimum Cooling Supply Air Temperature {C}
  0.02,                    !- Maximum Heating Supply Air Humidity Ratio {kgWater/kgDryAir}
  0.0077,                  !- Minimum Cooling Supply Air Humidity Ratio {kgWater/kgDryAir}
  NoLimit,                 !- Heating Limit
  0,                       !- Maximum Heating Air Flow Rate {m3/s}
  0,                       !- Maximum Sensible Heating Capacity {W}
  NoLimit,                 !- Cooling Limit
  ,                        !- Maximum Cooling Air Flow Rate {m3/s}
  0,                       !- Maximum Total Cooling Capacity {W}
  Assembly HVAC,           !- Heating Availability Schedule Name
  Assembly HVAC,           !- Cooling Availability Schedule Name
  None,                    !- Dehumidification Control Type
  0.7,                     !- Cooling Sensible Heat Ratio {dimensionless}
  60,                      !- Dehumidification Setpoint {percent}
  None,                    !- Humidification Control Type
  30,                      !- Humidification Setpoint {percent}
  None,                    !- Outdoor Air Method
  0.00944,                 !- Outdoor Air Flow Rate per Person {m3/s}
  ,                        !- Outdoor Air Flow Rate per Zone Floor Area {m3/s-m2}
  ,                        !- Outdoor Air Flow Rate per Zone {m3/s}
  ,                        !- Design Specification Outdoor Air Object Name
  None,                    !- Demand Controlled Ventilation Type
  NoEconomizer,            !- Outdoor Air Economizer Type
  None,                    !- Heat Recovery Type
  0.7,                     !- Sensible Heat Recovery Effectiveness {dimensionless}
  0.65;                    !- Latent Heat Recovery Effectiveness {dimensionless}

relative humidity temperature

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answered 2017-11-23 15:06:31 -0600

Avi gravatar image

updated 2017-11-23 16:07:04 -0600

I believe that the reason for the result you are showing is the value you assigned to Outdoor Air Method. When you leave it to default none you provide no outdoor air at all. So if you didn't set any infiltration, your zone is just cycling its own air. Here it's what written in the Input Output reference about Outdoor Air Method ;

Field: Outdoor Air Method The input must be either None, Flow/Zone, Flow/Person, Flow/Area, Sum, Maximum or DetailedSpecification. None means there is no outdoor air provided by this system. Flow/Zone means that the program will use the input of the field Outdoor Air Flow as the zone design outdoor air flow rate. Flow/Person means the program will use the input from the field Outdoor Air Flow per Person and the maximum occupancy to calculate a zone design outdoor air flow rate. Flow/Area means the program will use the input from the field Outdoor Air Flow per Zone Floor Area to calculated a zone design outdoor air flow rate. Sum means that the flows calculated from the fields Outdoor Air Flow per Person, Outdoor Air Flow per Area and Outdoor Air Flow per Zone will be added to obtain the zone design outdoor air flow rate. Maximum means that the maximum flow derived from Outdoor Air Flow per Person, Outdoor Air Flow per Area and Outdoor Air Flow per Zone will be used for the zone design outdoor air flow rate. The default is None..

You can do your test in OS by using that measure.

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Asked: 2017-05-19 01:50:45 -0600

Seen: 127 times

Last updated: Nov 28 '17