why negative internal convective heat gain during night?(EnergyPlus)

asked 2017-09-26 04:19:03 -0600

joooon

119 ●4

updated 2017-09-26 10:55:48 -0600

__AmirRoth__

4446 ●5 ●17 http://bleedinggreenna...

Hello now i am checking the zone air heat balance for each zone. but i just found that the internal convective heat gain from perimeter zones have negative results during night in winter.

actually, input/output reference describes internal convective heat gain rate as "The Zone Air Heat Balance Internal Convective Heat Gain Rate is the sum, in watts, of heat transferred to the zone air from all types of internal gains, including people, lights, equipment etc. This and the following provide results on the load components of the zone air heat balance. This field is not multiplied by zone or group multipliers."

and i don't get how internal convective heat gain can have negative results.

please teach me why this can be happened or what kinds of aspects are included in internal gains except people, lights, equipment.

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answered 2017-10-16 21:16:58 -0600

rraustad

13804 ●79 ●12 http://www.fsec.ucf.edu/

Zone Air Heat Balance Internal Convective Heat Gain Rate includes many components. At night most of the normal gains are zero. One of the others may be negative. If you see one of the objects below that are included in your input file, you can investigate further. Although some of these do not appear to be in the internal gains group, some of these objects have parasitic electricity use that would become internal heat gains or those that reject heat (e.g., motor heat from a fan or controls for a coil) to the space would also become a zone heat gain. If you cannot find which of these is causing the negative heat gain then the input file will be needed to find the culprit.

ZoneIntGainDeviceTypes:
 { "PEOPLE", "LIGHTS", "ELECTRICEQUIPMENT", "GASEQUIPMENT", "HOTWATEREQUIPMENT",
   "STEAMEQUIPMENT", "OTHEREQUIPMENT", "ZONEBASEBOARD:OUTDOORTEMPERATURECONTROLLED",
   "ZONECONTAMINANTSOURCEANDSINK:CARBONDIOXIDE", "WATERUSE:EQUIPMENT",
   "DAYLIGHTINGDEVICE:TUBULAR", "WATERHEATER:MIXED", "WATERHEATER:STRATIFIED",
   "THERMALSTORAGE:CHILLEDWATER:MIXED", "THERMALSTORAGE:CHILLEDWATER:STRATIFIED",
   "GENERATOR:FUELCELL", "GENERATOR:MICROCHP", "ELECTRICLOADCENTER:TRANSFORMER",
   "ELECTRICLOADCENTER:INVERTER:SIMPLE", "ELECTRICLOADCENTER:INVERTER:FUNCTIONOFPOWER",
   "ELECTRICLOADCENTER:INVERTER:LOOKUPTABLE", "ELECTRICLOADCENTER:STORAGE:BATTERY",
   "ELECTRICLOADCENTER:STORAGE:SIMPLE", "PIPE:INDOOR", "REFRIGERATION:CASE",
   "REFRIGERATION:COMPRESSORRACK", "REFRIGERATION:SYSTEM:CONDENSER:AIRCOOLED",
   "REFRIGERATION:TRANSCRITICALSYSTEM:GASCOOLER:AIRCOOLED", "REFRIGERATION:SYSTEM:SUCTIONPIPE",
   "REFRIGERATION:TRANSCRITICALSYSTEM:SUCTIONPIPEMT", "REFRIGERATION:TRANSCRITICALSYSTEM:SUCTIONPIPELT",
   "REFRIGERATION:SECONDARYSYSTEM:RECEIVER", "REFRIGERATION:SECONDARYSYSTEM:PIPE",
   "REFRIGERATION:WALKIN", "PUMP:VARIABLESPEED", "PUMP:CONSTANTSPEED", "PUMP:VARIABLESPEED:CONDENSATE",
   "HEADEREDPUMPS:VARIABLESPEED", "HEADEREDPUMPS:CONSTANTSPEED",
   "ZONECONTAMINANTSOURCEANDSINK:GENERICCONTAMINANT", "PLANTCOMPONENT:USERDEFINED",
   "COIL:USERDEFINED", "ZONEHVAC:FORCEDAIR:USERDEFINED", "AIRTERMINAL:SINGLEDUCT:USERDEFINED",
   "COIL:COOLING:DX:SINGLESPEED:THERMALSTORAGE", "ELECTRICEQUIPMENT:ITE:AIRCOOLED",
   "COIL:COOLING:DX:SINGLESPEED", "COIL:HEATING:DX:SINGLESPEED", "COIL:COOLING:DX:TWOSPEED",
   "COIL:COOLING:DX:MULTISPEED", "COIL:HEATING:DX:MULTISPEED",
   "ELECTRICLOADCENTER:STORAGE:CONVERTER","FAN:SYSTEMMODEL"}

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Thank you very much! Actually after some investigations, i found that a curtain for shading causes negative internal gains during night. but i still don't get why curtains cause negative internal gain. do you know how to investigate the internal convective thermal gains from shading devices? What kind of variable need to be checked?

joooon ( 2017-10-19 01:40:28 -0600 )edit

See WindowTests.idf in ExampleFiles folder. Reports for shading (there are others) in rdd are:

Output:Variable,*,Surface Window Shading Device Absorbed Solar Radiation Rate,Hourly;
Output:Variable,*,Surface Window Shading Device Absorbed Solar Radiation Energy,Hourly;
Output:Variable,*,Debug Surface Solar Shading Model DifShdgRatioIsoSky,Hourly;
Output:Variable,*,Debug Surface Solar Shading Model DifShdgRatioHoriz,Hourly;
Output:Variable,*,Debug Surface Solar Shading Model WithShdgIsoSky,Hourly;
Output:Variable,*,Debug Surface Solar Shading Model WoShdgIsoSky,Hourly;