I¢m having trouble controlling occupant air temperature in a Mundt zone. I have a complex shape zone, hemispherical with approximately 50 ft diameter and 252 surfaces. I have entered all the surfaces as appropriate Mundt room nodes. I have a Mundt control node 1.75m above the floor and supply air entering 0.5m above the floor from a Purchased Air object at 13 degC. Return air exits near the ceiling. I don¢t have any internal loads yet, the convective wall loads affect the space.
I have tried the model with DIRECT and INDIRECT coupling.
With direct coupling I get a variable supply air flow, but it responds to the zone average temperature and not the control node. When zone average is below the cooling set point, the flow is off. As the zone average temperature rises above set point (control node is still lower than set point), air flow increases and the average air temperature gets controlled to the set point with little room stratification except that the control node is very cold.
With indirect coupling I have a max flow limit from the Purchased Air Object, lots of stratification heating and stone cold occupied zone. The average air temperature floats above the set point and the control node chills to nearly the supply air temperature.
Can I have a cold supply air temperature and limit flow to keep the control node conditioned rather than working on the average zone air temperature?
Do I need to name the control node the same name as the average zone temperature?
If I increase the supply air temperature, how do I get an appropriate supply air flow that doesn¢t also cool the whole space?
Excerpts of the .idf file:
ROOMAIR MODEL,
MUNDT For MAIN, !- Room-Air Model Name
MAIN, !- Zone Name
MUNDT, !- Room-Air Modeling Type
INDIRECT; !- Air Temperature Coupling Strategy
!- =========== ALL OBJECTS IN CLASS: ROOMAIR NODE ===========
!
!These are inputs for a stratification model for air distribution in the MAIN
!Zone. Proper operation of this calculation has not been verified. 10 July 2008
!
ROOMAIR NODE,
MAIN_Inlet, !- Node Name
INLET, !- Node Type
MAIN, !- Name of Zone to Which the Air Node Belongs
0.5; !- Height of Nodal Control Volume Center {m}
ROOMAIR NODE,
Main_Floor, !- Node Name
FLOOR, !- Node Type
MAIN, !- Name of Zone to Which the Air Node Belongs
0.05, !- Height of Nodal Control Volume Center {m}
MAIN_FLOOR_1, !- surface name #1
MAIN_FLOOR_2, !- surface name #2
MAIN_FLOOR_3, !- surface name #3
MAIN_FLOOR_4, !- surface name #4
MAIN_FLOOR_5, !- surface name #5
MAIN_FLOOR_6, !- surface name #6
MAIN_FLOOR_7, !- surface name #7
MAIN_FLOOR_8, !- surface name #8
MAIN_FLOOR_9, !- surface name #9
MAIN_FLOOR_10, !- surface name #10
MAIN_FLOOR_11, !- surface name #11
MAIN_FLOOR_12, !- surface name #12
MAIN_FLOOR_13, !- surface name #13
MAIN_FLOOR_14, !- surface name #14
MAIN_FLOOR_15, !- surface name #15
MAIN_FLOOR_16, !- surface name #16
MAIN_FLOOR_17, !- surface name #17
MAIN_FLOOR_18; !- surface name #18
ROOMAIR NODE,
MAIN_Occupied, !- Node Name
CONTROL, !- Node Type
MAIN, !- Name of Zone to Which the Air Node Belongs
1.75; !- Height of Nodal Control Volume Center {m}
ROOMAIR NODE,
MAIN_Vent, !- Node Name
RETURN, !- Node Type
MAIN, !- Name of Zone to Which the Air Node Belongs
27; !- Height of Nodal Control Volume Center {m}
!- =========== ALL OBJECTS IN CLASS: MUNDT MODEL CONTROLS ===========
MUNDT MODEL CONTROLS,
MAIN, !- Zone Name
1, !- Fraction of internal loads from the convective Floor Air
0; !- Fraction of internal loads from the Infiltration Air
NODE LIST,
Inlet_MAIN, !- Node List Name
MAIN_Inlet; !- Node_ID_1
CONTROLLED ZONE EQUIP CONFIGURATION,
MAIN, !- Zone Name
MAIN_Equip, !- List Name: Zone Equipment
Inlet_MAIN, !- Node List or Node Name: Zone Air Inlet Node(s)
, !- Node List or Node Name: Zone Air Exhaust Node(s)
MAIN_Occupied, !- Zone Air Node Name
Return_MAIN; !- Zone Return Air Node Name
ZONE EQUIPMENT LIST,
MAIN_Equip, !- Name
PURCHASED AIR, !- KEY--Zone Equipment Type 1
Air_MAIN, !- Type Name 1
1, !- Cooling Priority 1
1; !- Heating Priority 1
PURCHASED AIR,
Air_MAIN, !- Purchased Air Name
MAIN_Inlet, !- Zone Supply Air Node Name
50, !- Heating Supply Air Temp {C}
13, !- Cooling Supply Air Temp {C}
0.00624, !- Heating Supply Air Humidity Ratio {kg-H2O/kg-air}
0.00624, !- Cooling Supply Air Humidity Ratio {kg-H2O/kg-air}
LIMIT, !- heating limit
5, !- Maximum heating air flow rate {m3/s}
LIMIT, !- cooling limit
5, !- Maximum cooling air flow rate {m3/s}
NO OUTSIDE AIR, !- outside air
0.01, !- Outside air flow rate {m3/s}
Always_On, !- heating availability schedule
Always_On; !- cooling availability schedule
ZONE CONTROL:THERMOSTATI C,
Stat_MAIN, !- Thermostat Name
MAIN, !- Zone Name
MAIN_Control_ Type, !- Control Type SCHEDULE Name
Dual Setpoint with Deadband, !- Control Type #1
MAIN_DeadBand; !- Control Type Name #1
DUAL SETPOINT WITH DEADBAND,
MAIN_DeadBand, !- Name
Heat_Main, !- Heating Setpoint Temperature SCHEDULE Name
Cool_Main; !- Cooling Setpoint Temperature SCHEDULE Name
Ned Lyon
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| Engineering of Structures and Building Enclosures
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