Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page

# Natural ventilation to reduce cooling loads

I'm modeling a very simple house with a single thermal zone with CAV DX coil cooling with a single air duct. In order to test cooling loads reduction with window opening, I constructed a simple AFN for natural ventilation, using NoMultizoneOr Distribution and Surface Average Calculation method (I am a novice to Airflownetwork (AFN) though).

However, even though the AFN is set, I find no change in cooling loads. Can anyone explain why? and how to fix this problem? Thanks in advance. My inputs are as follows:

!-   ===========  ALL OBJECTS IN CLASS: AIRFLOWNETWORK:SIMULATIONCONTROL ===========

AirflowNetwork:SimulationControl,

EllisAirNetwork,         !- Name
NoMultizoneOrDistribution,  !- AirflowNetwork Control
SurfaceAverageCalculation,  !- Wind Pressure Coefficient Type
,                        !- AirflowNetwork Wind Pressure Coefficient Array Name
,                        !- Height Selection for Local Wind Speed Calculation
LowRise,                 !- Building Type
500,                     !- Maximum Number of Iterations {dimensionless}
LinearInitializationMethod,  !- Initialization Type
0.0001,                  !- Relative Airflow Convergence Tolerance {dimensionless}
0.000001,                !- Absolute Airflow Convergence Tolerance {kg/s}
-.5,                     !- Convergence Acceleration Limit {dimensionless}
90,                      !- Azimuth Angle of Long Axis of Building {deg}
0.95;                    !- Ratio of Building Width Along Short Axis to Width Along Long Axis

!-   ===========  ALL OBJECTS IN CLASS: AIRFLOWNETWORK:MULTIZONE:ZONE ===========

AirflowNetwork:MultiZone:Zone,

Thermal Zone 1,          !- Zone Name
Constant,                !- Ventilation Control Mode
Ellis House ClgSetp 1,   !- Ventilation Control Zone Temperature Setpoint Schedule Name
0.5,                     !- Minimum Venting Open Factor {dimensionless}
3,                       !- Indoor and Outdoor Temperature Difference Lower Limit For Maximum Venting Open Factor {deltaC}
10,                      !- Indoor and Outdoor Temperature Difference Upper Limit for Minimun Venting Open Factor {deltaC}
0.0,                     !- Indoor and Outdoor Enthalpy Difference Lower Limit For Maximum Venting Open Factor {deltaJ/kg}
300000.0;                !- Indoor and Outdoor Enthalpy Difference Upper Limit for Minimun Venting Open Factor {deltaJ/kg}

!-   ===========  ALL OBJECTS IN CLASS: AIRFLOWNETWORK:MULTIZONE:SURFACE ===========

AirflowNetwork:MultiZone:Surface,

Sub Surface 1,           !- Surface Name
VentOpening,             !- Leakage Component Name
0.6,                     !- Window/Door Opening Factor, or Crack Factor {dimensionless}
Constant,                !- Ventilation Control Mode
,                        !- Ventilation Control Zone Temperature Setpoint Schedule Name
0.1,                     !- Minimum Venting Open Factor {dimensionless}
2,                       !- Indoor and Outdoor Temperature Difference Lower Limit For Maximum Venting Open Factor {deltaC}
3,                       !- Indoor and Outdoor Temperature Difference Upper Limit for Minimun Venting Open Factor {deltaC}
,                        !- Indoor and Outdoor Enthalpy Difference Lower Limit For Maximum Venting Open Factor {deltaJ/kg}
300000,                  !- Indoor and Outdoor Enthalpy Difference Upper Limit for Minimun Venting Open Factor {deltaJ/kg}
Always On;               !- Venting Availability Schedule Name

AirflowNetwork:MultiZone:Surface,

Sub Surface 4,           !- Surface Name
VentOpening,             !- Leakage Component Name
0.4,                     !- Window/Door Opening Factor, or Crack Factor {dimensionless}
Constant,                !- Ventilation Control Mode
,                        !- Ventilation Control Zone Temperature Setpoint Schedule Name
0.1,                     !- Minimum Venting Open Factor {dimensionless}
1,                       !- Indoor and Outdoor Temperature Difference Lower Limit For Maximum Venting Open Factor {deltaC}
3,                       !- Indoor and Outdoor Temperature Difference Upper Limit for Minimun Venting Open Factor {deltaC}
,                        !- Indoor and Outdoor Enthalpy Difference Lower Limit For Maximum Venting Open Factor {deltaJ/kg}
300000,                  !- Indoor and Outdoor Enthalpy Difference Upper Limit for Minimun Venting Open Factor {deltaJ/kg}
Always On;               !- Venting Availability Schedule Name

!-   ===========  ALL OBJECTS IN CLASS: AIRFLOWNETWORK:MULTIZONE:COMPONENT:SIMPLEOPENING ...
edit retag close merge delete

Sort by ยป oldest newest most voted

NoMultizoneOrDistribution allows simple calculations only. Here is IORef. Energy+.idd note for input field AirflowNetwork Control in AirflowNetwork:SimulationControl object says

\note NoMultizoneOrDistribution: Only perform Simple calculations (objects ZoneInfiltration:*,
\note ZoneVentilation:*, ZoneMixing, ZoneCrossMixing, ZoneRefrigerationDoorMixing,
\note ZoneAirBalance:OutdoorAir, ZoneEarthtube, ZoneThermalChimney, and ZoneCoolTower:Shower);


Did you try MultizoneWithoutDistribution?

p.s. would have put it as comment rather than answer but couldn't do so because of word limit.

more

Chandan is correct. The AFN is turned off if you select NoMultizoneOrDistribution.

( 2015-12-14 09:59:08 -0500 )edit