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How to model a refrigerated warehouse in OpenStudio?

asked 2015-12-28 16:55:56 -0500

updated 2015-12-29 08:43:44 -0500

Should large refrigerated spaces over 30,000 sqft with setpoints ranging from -20°F to 35°F be modeled using the refrigeration tab of the HVAC Systems side tab of OpenStudio 1.9, or by using an air loop with schedules to apply setpoints to each zone? Or should it be both, that is, should the refrigeration system (see screenshot) or the zones they are in have an HVAC loop?

I currently have the refrigerated spaces drawn as unique spaces and thermal zones, and have applied a refrigerated walkin case for each zone. I then applied constructions, racks, zones, etc under the system grid view. I can run ideal air loads, but when I turn them off and run the model I get several severe errors.

"Severe * GetRefrigerationInput: Refrigeration:WalkIn="COOLER 132" System Node Number not found for Zone 1 Name = THERMAL ZONE: L1 II COOLER 132 * ~~~ ** .. Walk Ins must reference a controlled Zone (appear in a ZoneHVAC:EquipmentConnections object."

"Severe ** GetRefrigerationInput: Refrigeration:System="REFRIGERATION SYSTEM", System Node Number not found for Suction Piping Zone Name = THERMAL ZONE: L1 II COOLER 132 even though Sum UA Suction Piping is greater than zero. Suction piping heat gain cannot be calculated unless a Zone is defined to deterimine the environmental temperature surrounding the piping."

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I don't know if Open Studio has it, but in EnergyPlus the Refrigeration:AirChiller object is intended for refrigerated warehouse applications. In general the usual air system HVAC models will not work well for those low temperatures.

Archmage gravatar imageArchmage ( 2015-12-29 09:12:21 -0500 )edit

@Archmage, I cannot find the Refrigeration:AirChiller object in OpenStudio versions 1.6 to 1.9. Does anyone know if this has been added to OS? I looked under the HVAC Systems side tab library.

kramerica gravatar imagekramerica ( 2015-12-30 12:52:40 -0500 )edit
1

Looks like it is in the API in 1.10, but not sure when added. https://openstudio-sdk-documentation.s3.amazonaws.com/cpp/OpenStudio-1.10.0-doc/model/html/classopenstudio_1_1model_1_1_refrigeration_air_chiller.html

I don't see it in the GUI library yet.

David Goldwasser gravatar imageDavid Goldwasser ( 2015-12-30 13:35:58 -0500 )edit

Is there a measure or code I can use to get this working in OS 1.9? Or is there another workaround without having to work in EnergyPlus?

kramerica gravatar imagekramerica ( 2015-12-30 14:16:43 -0500 )edit

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answered 2016-01-07 10:19:19 -0500

As @Archmage suggested, what you want is probably the Refrigeration:AirChiller. This is available in the OS API but not in the library as of 1.9.0. Here's some code that you can use in a Measure to add one:

# Create an air chiller
air_chiller = OpenStudio::Model::RefrigerationAirChiller.new(model, defrost_schedule)

# Hook it up to the zone
air_chiller.addToThermalZone(zone_1)

# Set the air chiller properties
air_chiller.setCapacityRatingType("UnitLoadFactorSensibleOnly")
air_chiller.setRatedUnitLoadFactor(0.5)
air_chiller.setRatedCapacity(1000)
air_chiller.setRatedRelativeHumidity(0.2)
# ...etc.  See the documentation for a list of methods
# for all of the fields

The API documentation for Refrigeration:AirChiller gives you a list of all the methods you can use to set the rest of the inputs for this object.

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2

You will also need to add the AirChiller to a Refrigeration System.

# Create a refrigeration system
ref_system = OpenStudio::Model::RefrigerationSystem.new(model)

# Create an air chiller
air_chiller = OpenStudio::Model::RefrigerationAirChiller.new(model, defrost_schedule)

# Hook it up to the zone
air_chiller.addToThermalZone(zone_1)

# Add to ref system
ref_system.addAirChiller(air_chiller)
MarkAdams gravatar imageMarkAdams ( 2016-01-07 14:07:27 -0500 )edit

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Asked: 2015-12-28 16:55:56 -0500

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Last updated: Jan 07 '16