Class: AirWallZoneMixing

Inherits:
OpenStudio::Measure::ModelMeasure
  • Object
show all
Defined in:
lib/measures/air_wall_zone_mixing/measure.rb

Overview

start the measure

Instance Method Summary collapse

Instance Method Details

#arguments(model) ⇒ Object

define the arguments that the user will input



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# File 'lib/measures/air_wall_zone_mixing/measure.rb', line 32

def arguments(model)
  args = OpenStudio::Measure::OSArgumentVector.new

  # the name of the space to add to the model
  zone_mixing_coef = OpenStudio::Measure::OSArgument.makeDoubleArgument('zone_mixing_coef', true)
  zone_mixing_coef.setDisplayName('Cross Mixing Coefficient')
  zone_mixing_coef.setDescription('Cross Mixing flow rate = zone mixing coefficient * zone volume/sqrt(thermal zone volume/(air wall area*zone height))')
  zone_mixing_coef.setDefaultValue(1.0)
  args << zone_mixing_coef

  # the name of the space to add to the model
  add_zone_mixing_variables = OpenStudio::Measure::OSArgument.makeBoolArgument('add_zone_mixing_variables', true)
  add_zone_mixing_variables.setDisplayName('Add Zone Mixing Output Variable Requests')
  add_zone_mixing_variables.setDefaultValue(true)
  args << add_zone_mixing_variables

  return args
end

#description ⇒ Object

human readable description



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# File 'lib/measures/air_wall_zone_mixing/measure.rb', line 19

def description
  return "This measure replaces conductive heat transfer with zone mixing wherever air walls are used on matched surfaces or sub-surfaces for walls. A user argument is exposed for a coefficient that represents a target air changes per hour (ACH) for a room where the zone volume/the air wall surface area is the same as its zone height. As the room gets deeper the additional airflow per unit of depth decreases. If two zones have different mixing estimates, the lower will be used. If a smaller portion of an inter-zone wall is an air wall, that will also decrease zone mixing airflow. A construction will be hard assigned to the matched surfaces using the air wall, and the then boundary condition will be changed to adiabatic. This will avoid including both air mixing and conductive transfer across zones. Zone mixing objects will also be made for sub-surface air walls, but they can't be made adiabatic unless their base surface also is. A warning will be issued if that happens"
end

#modeler_description ⇒ Object

human readable description of modeling approach



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# File 'lib/measures/air_wall_zone_mixing/measure.rb', line 24

def modeler_description
  return "The formula used to determine the design flow rate is the zone mixing coefficient * zone volume/sqrt(zone volume / (air wall area * zone height).

Zone mixing will only be added where there is an air wall and where the matched surfaces belong to spaces in different thermal zones and the base surface type is a wall. Currently floors are not addressed by this measure. Air walls in spaces that are part of the same thermal zone will be left alone. The intended use case is a single base surface that spans the room or one or more sub-surface that spans a portion of it. If you have multiple air wall base surfaces matched between the same zones you may get higher than expected zone mixing."
end

#name ⇒ Object

human readable name



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# File 'lib/measures/air_wall_zone_mixing/measure.rb', line 14

def name
  return 'Air Wall Zone Mixing'
end

#run(model, runner, user_arguments) ⇒ Object

define what happens when the measure is run



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# File 'lib/measures/air_wall_zone_mixing/measure.rb', line 52

def run(model, runner, user_arguments)
  super(model, runner, user_arguments)

  # use the built-in error checking
  if !runner.validateUserArguments(arguments(model), user_arguments)
    return false
  end

  # assign the user inputs to variables
  zone_mixing_coef = runner.getDoubleArgumentValue('zone_mixing_coef', user_arguments)
  add_zone_mixing_variables = runner.getBoolArgumentValue('add_zone_mixing_variables', user_arguments)

  # report initial condition of model
  runner.registerInitialCondition("The building started with #{model.getZoneMixings.size} Zone Mixing Objects.")

  # array of surfaces and sub-surfaces already processed
  processed_surfaces = []
  processed_sub_surfaces = []

  # populate a hash of zone volumes ahead of time
  zone_volumes = {}
  zone_heights = {}
  model.getThermalZones.sort.each do |zone|
    volume_counter = 0
    max_space_height = 0
    zone.spaces.each do |space|
      volume_counter += space.volume
      min_space_zvalue = OpenstudioStandards::Geometry.surfaces_get_z_values(space.surfaces).sort.first # this expects an array of surfaces
      max_space_zvalue = OpenstudioStandards::Geometry.surfaces_get_z_values(space.surfaces).sort.last # this expects an array of surfaces
      if max_space_zvalue - min_space_zvalue > max_space_height
        max_space_height = max_space_zvalue - min_space_zvalue
      end
    end
    zone_volumes[zone] = volume_counter
    zone_heights[zone] = max_space_height
    puts "volume of #{zone.name} is #{volume_counter}"
  end

  model.getThermalZones.sort.each do |zone|
    zone.spaces.each do |space|
      space.surfaces.each do |surface|
        next if processed_surfaces.include? surface
        next if surface.surfaceType != 'Wall'
        next if surface.adjacentSurface.is_initialized != true
        adiabatic = false
        boundary_surface = surface.adjacentSurface.get
        processed_surfaces << surface
        processed_surfaces << boundary_surface
        if boundary_surface.space.is_initialized && boundary_surface.space.get.thermalZone.is_initialized
          boundary_object_zone = boundary_surface.space.get.thermalZone.get
          if zone.multiplier != boundary_object_zone.multiplier
            runner.registerWarning("#{zone.name} and #{boundary_object_zone.name} don't have the same multiplier. Won't alter surfaces or add zone mixing for this pair of zones")
            next
          end
          if boundary_object_zone != zone
            # check surface constructions
            if surface.isAirWall
              air_wall_area = surface.grossArea
              zone_a_volume = zone_volumes[zone]
              zone_a_height = zone_heights[zone]
              zone_b_volume = zone_volumes[boundary_object_zone]
              zone_b_height = zone_heights[boundary_object_zone]
              if zone_a_volume <= zone_b_volume
                zone_volume = zone_a_volume
                zone_height = zone_a_height
              else
                zone_volume = zone_b_volume
                zone_height = zone_b_height
              end

              # calculate target zone mixing values
              # zone_mixing_coef * zone_volume m^3 / (Math.sqrt(zone_volume m^3/ air_wall_area m^2 * zone_height m))
              target_zone_mixing_hour_si = zone_mixing_coef * zone_volume / Math.sqrt(zone_volume / (air_wall_area * zone_height))
              target_zone_mixing_si = target_zone_mixing_hour_si / 3600.0
              zone_mixing_a = OpenStudio::Model::ZoneMixing.new(zone)
              zone_mixing_a.setSourceZone(boundary_object_zone)
              zone_mixing_a.setDesignFlowRate(target_zone_mixing_si)
              zone_mixing_a.setDeltaTemperature(0.0)
              zone_mixing_b = OpenStudio::Model::ZoneMixing.new(boundary_object_zone)
              zone_mixing_b.setSourceZone(zone)
              zone_mixing_b.setDesignFlowRate(target_zone_mixing_si)
              zone_mixing_b.setDeltaTemperature(0.0)
              target_zone_mixing_ip = OpenStudio.convert(target_zone_mixing_si, 'm^3/s', 'cfm').get
              runner.registerInfo("Add zone mixing between #{zone.name} and #{boundary_object_zone.name} with flowrate of #{target_zone_mixing_ip.round(2)} cfm")
              adiabatic = true
            end
            # check sub_surfaces constructions
            surface.subSurfaces.each do |sub_surface|
              next if sub_surface.adjacentSubSurface.is_initialized != true
              boundary_sub_surface = sub_surface.adjacentSubSurface.get
              processed_sub_surfaces << sub_surface
              processed_sub_surfaces << boundary_sub_surface
              if sub_surface.isAirWall
                air_wall_area = surface.grossArea
                zone_a_volume = zone_volumes[zone]
                zone_a_height = zone_heights[zone]
                zone_b_volume = zone_volumes[boundary_object_zone]
                zone_b_height = zone_heights[boundary_object_zone]
                if zone_a_volume <= zone_b_volume
                  zone_volume = zone_a_volume
                  zone_height = zone_a_height
                else
                  zone_volume = zone_b_volume
                  zone_height = zone_b_height
                end

                # calculate target zone mixing values
                # zone_mixing_coef * zone_volume m^3 / (Math.sqrt(zone_volume m^3/ air_wall_area m^2 * zone_height m))
                target_zone_mixing_hour_si = zone_mixing_coef * zone_volume / Math.sqrt(zone_volume / (air_wall_area * zone_height))
                target_adjusted_sub_surface_fraction = target_zone_mixing_hour_si * sub_surface.grossArea / surface.grossArea
                target_zone_mixing_si = target_adjusted_sub_surface_fraction / 3600.0
                zone_mixing_a = OpenStudio::Model::ZoneMixing.new(zone)
                zone_mixing_a.setSourceZone(boundary_object_zone)
                zone_mixing_a.setDesignFlowRate(target_zone_mixing_si)
                zone_mixing_a.setDeltaTemperature(0.0)
                zone_mixing_b = OpenStudio::Model::ZoneMixing.new(boundary_object_zone)
                zone_mixing_b.setSourceZone(zone)
                zone_mixing_b.setDesignFlowRate(target_zone_mixing_si)
                zone_mixing_b.setDeltaTemperature(0.0)
                target_zone_mixing_ip = OpenStudio.convert(target_zone_mixing_si, 'm^3/s', 'cfm').get
                runner.registerInfo("Add zone mixing between #{zone.name} and #{boundary_object_zone.name} with flowrate of #{target_zone_mixing_ip.round(2)} cfm")
                sub_surface.setConstruction(sub_surface.construction.get) # is there an easier way to set to air wall
                boundary_sub_surface.setConstruction(boundary_sub_surface.construction.get) # is there an easier way to set to air wall
                if !surface.isAirWall
                  runner.registerWarning("Sub-surfaces shared with #{zone.name} and #{boundary_object_zone.name} can't be made adiabatic. Conductive heat transfer will remain in the model for these sub-surfaces.")
                end
              end
            end
            if adiabatic # moved this later to handle air wall sub-surface hosted by air wall base surface
              surface.setConstruction(surface.construction.get) # is there an easier way to set to air wall
              boundary_surface.setConstruction(boundary_surface.construction.get) # is there an easier way to set to air wall
              surface.setOutsideBoundaryCondition('Adiabatic')
              boundary_surface.setOutsideBoundaryCondition('Adiabatic')
            end
          end
        else
          runner.registerWarning("didn't find thermal zone for #{boundary_surface.name}")
        end
      end
    end
  end

  # add output reports
  if add_zone_mixing_variables
    OpenStudio::Model::OutputVariable.new('Zone Mixing Volume', model)
    OpenStudio::Model::OutputVariable.new('Zone Mixing Current Density Air Volume Flow Rate', model)
    OpenStudio::Model::OutputVariable.new('Zone Mixing Standard Density Air Volume Flow Rate', model)
    OpenStudio::Model::OutputVariable.new('Zone Mixing Mass Flow Rate', model)
    OpenStudio::Model::OutputVariable.new('Zone Mixing Receiving Air Mass Flow Rate', model)
    OpenStudio::Model::OutputVariable.new('Zone Mixing Source Air Mass Flow Rate', model)
  end

  # report final condition of model
  runner.registerFinalCondition("The building finished with #{model.getZoneMixings.size} Zone Mixing Objects.")

  return true
end