Merge pull request #1041 from NREL/cfis-airflow-fraction

New CFIS `VentilationOnlyModeAirflowFraction` input

Changelog.md

@@ -6,6 +6,7 @@ __New Features__
 - Allows specifying a `StormWindow` element for windows/skylights; U-factors and SHGCs are automatically adjusted.
 - Allows an optional `AirInfiltrationMeasurement/InfiltrationHeight` input.
 - Allows an optional `Battery/UsableCapacity` input; now defaults to 0.9 x NominalCapacity (previously 0.8).
+- For CFIS systems, allows an optional `extension/VentilationOnlyModeAirflowFraction` input to address duct losses during ventilation only mode.
 - Adds support for shared hot water recirculation systems controlled by temperature.
 - The `WaterFixturesUsageMultiplier` input now also applies to general water use internal gains and recirculation pump energy (for some control types).
 - Relaxes requirement for `ConditionedFloorAreaServed` for air distribution systems; now only needed if duct surface areas not provided.

HPXMLtoOpenStudio/measure.xml

@@ -3,8 +3,8 @@
   <schema_version>3.0</schema_version>
   <name>hpxm_lto_openstudio</name>
   <uid>b1543b30-9465-45ff-ba04-1d1f85e763bc</uid>
-  <version_id>2a19d7d9-f4a4-4b5b-b8db-ba93dcdaa3d3</version_id>
-  <version_modified>20220415T140250Z</version_modified>
+  <version_id>01aaadd5-0fae-4ec3-b903-f4253a8a70a2</version_id>
+  <version_modified>20220418T214931Z</version_modified>
   <xml_checksum>D8922A73</xml_checksum>
   <class_name>HPXMLtoOpenStudio</class_name>
   <display_name>HPXML to OpenStudio Translator</display_name>
@@ -409,18 +409,6 @@
       <usage_type>test</usage_type>
       <checksum>2CB59B38</checksum>
     </file>
-    <file>
-      <filename>hpxml_defaults.rb</filename>
-      <filetype>rb</filetype>
-      <usage_type>resource</usage_type>
-      <checksum>46EF98A6</checksum>
-    </file>
-    <file>
-      <filename>test_defaults.rb</filename>
-      <filetype>rb</filetype>
-      <usage_type>test</usage_type>
-      <checksum>E1E3069B</checksum>
-    </file>
     <file>
       <filename>hpxml_schematron/HPXMLvalidator.xml</filename>
       <filetype>xml</filetype>
@@ -439,24 +427,6 @@
       <usage_type>test</usage_type>
       <checksum>E276D4D3</checksum>
     </file>
-    <file>
-      <filename>hpxml.rb</filename>
-      <filetype>rb</filetype>
-      <usage_type>resource</usage_type>
-      <checksum>B291B794</checksum>
-    </file>
-    <file>
-      <filename>hpxml_schematron/EPvalidator.xml</filename>
-      <filetype>xml</filetype>
-      <usage_type>resource</usage_type>
-      <checksum>68EC4628</checksum>
-    </file>
-    <file>
-      <filename>airflow.rb</filename>
-      <filetype>rb</filetype>
-      <usage_type>resource</usage_type>
-      <checksum>F45F8526</checksum>
-    </file>
     <file>
       <filename>version.rb</filename>
       <filetype>rb</filetype>
@@ -528,5 +498,35 @@
       <usage_type>resource</usage_type>
       <checksum>3B95C662</checksum>
     </file>
+    <file>
+      <filename>hpxml_defaults.rb</filename>
+      <filetype>rb</filetype>
+      <usage_type>resource</usage_type>
+      <checksum>22C49391</checksum>
+    </file>
+    <file>
+      <filename>test_defaults.rb</filename>
+      <filetype>rb</filetype>
+      <usage_type>test</usage_type>
+      <checksum>23AC8D71</checksum>
+    </file>
+    <file>
+      <filename>hpxml.rb</filename>
+      <filetype>rb</filetype>
+      <usage_type>resource</usage_type>
+      <checksum>7C662926</checksum>
+    </file>
+    <file>
+      <filename>hpxml_schematron/EPvalidator.xml</filename>
+      <filetype>xml</filetype>
+      <usage_type>resource</usage_type>
+      <checksum>7B807A24</checksum>
+    </file>
+    <file>
+      <filename>airflow.rb</filename>
+      <filetype>rb</filetype>
+      <usage_type>resource</usage_type>
+      <checksum>9CC1B4EF</checksum>
+    </file>
   </files>
 </measure>

HPXMLtoOpenStudio/resources/airflow.rb

@@ -84,7 +84,7 @@ def self.apply(model, runner, weather, spaces, hpxml, cfa, nbeds,
     # Apply ducts
 
     duct_systems.each do |ducts, object|
-      apply_ducts(model, ducts, object)
+      apply_ducts(model, ducts, object, vent_fans_mech)
     end
 
     # Apply infiltration/ventilation
@@ -597,7 +597,7 @@ def self.initialize_fan_objects(model, osm_object)
     end
   end
 
-  def self.apply_ducts(model, ducts, object)
+  def self.apply_ducts(model, ducts, object, vent_fans_mech)
     ducts.each do |duct|
       duct.rvalue = get_duct_insulation_rvalue(duct.rvalue, duct.side) # Convert from nominal to actual R-value
       if not duct.loc_schedule.nil?
@@ -1062,10 +1062,11 @@ def self.apply_ducts(model, ducts, object)
 
       if @cfis_airloop.values.include? object
 
-        # Calculate CFIS duct losses
+        # Calculate additional CFIS duct losses during fan-only mode
         cfis_id = @cfis_airloop.key(object)
+        vent_mech = vent_fans_mech.select { |vfm| vfm.id == cfis_id }[0]
         duct_program.addLine("If #{@cfis_f_damper_extra_open_var[cfis_id].name} > 0")
-        duct_program.addLine("  Set cfis_m3s = (#{@fan_mfr_max_var[object].name} / 1.16097654)") # Density of 1.16097654 was back calculated using E+ results
+        duct_program.addLine("  Set cfis_m3s = (#{@fan_mfr_max_var[object].name} * #{vent_mech.cfis_vent_mode_airflow_fraction} / 1.16097654)") # Density of 1.16097654 was back calculated using E+ results
         duct_program.addLine("  Set #{@fan_rtf_var[object].name} = #{@cfis_f_damper_extra_open_var[cfis_id].name}") # Need to use global vars to sync duct_program and infiltration program of different calling points
         duct_program.addLine("  Set #{ah_vfr_var.name} = #{@fan_rtf_var[object].name}*cfis_m3s")
         duct_program.addLine("  Set rho_in = (@RhoAirFnPbTdbW #{@pbar_sensor.name} #{@tin_sensor.name} #{@win_sensor.name})")

HPXMLtoOpenStudio/resources/hpxml.rb

@@ -4208,7 +4208,7 @@ class VentilationFan < BaseElement
              :is_shared_system, :in_unit_flow_rate, :fraction_recirculation, :used_for_garage_ventilation,
              :preheating_fuel, :preheating_efficiency_cop, :preheating_fraction_load_served, :precooling_fuel,
              :precooling_efficiency_cop, :precooling_fraction_load_served, :calculated_flow_rate,
-             :delivered_ventilation]
+             :delivered_ventilation, :cfis_vent_mode_airflow_fraction]
     attr_accessor(*ATTRS)
 
     def distribution_system
@@ -4386,6 +4386,7 @@ def to_oga(doc)
       end
       XMLHelper.add_extension(ventilation_fan, 'FlowRateNotTested', @flow_rate_not_tested, :boolean) unless @flow_rate_not_tested.nil?
       XMLHelper.add_extension(ventilation_fan, 'FanPowerDefaulted', @fan_power_defaulted, :boolean) unless @fan_power_defaulted.nil?
+      XMLHelper.add_extension(ventilation_fan, 'VentilationOnlyModeAirflowFraction', @cfis_vent_mode_airflow_fraction, :float, @cfis_vent_mode_airflow_fraction_isdefaulted) unless @cfis_vent_mode_airflow_fraction.nil?
     end
 
     def from_oga(ventilation_fan)
@@ -4422,6 +4423,7 @@ def from_oga(ventilation_fan)
       @precooling_fraction_load_served = XMLHelper.get_value(ventilation_fan, 'extension/PreCooling/FractionVentilationCoolLoadServed', :float)
       @flow_rate_not_tested = XMLHelper.get_value(ventilation_fan, 'extension/FlowRateNotTested', :boolean)
       @fan_power_defaulted = XMLHelper.get_value(ventilation_fan, 'extension/FanPowerDefaulted', :boolean)
+      @cfis_vent_mode_airflow_fraction = XMLHelper.get_value(ventilation_fan, 'extension/VentilationOnlyModeAirflowFraction', :float)
     end
   end
 

HPXMLtoOpenStudio/resources/hpxml_defaults.rb

@@ -1423,6 +1423,10 @@ def self.apply_ventilation_fans(hpxml, infil_measurements, weather, cfa, nbeds)
         vent_fan.fan_power = (vent_fan.flow_rate * Airflow.get_default_mech_vent_fan_power(vent_fan)).round(1)
         vent_fan.fan_power_isdefaulted = true
       end
+      if vent_fan.cfis_vent_mode_airflow_fraction.nil? && (vent_fan.fan_type == HPXML::MechVentTypeCFIS)
+        vent_fan.cfis_vent_mode_airflow_fraction = 1.0
+        vent_fan.cfis_vent_mode_airflow_fraction_isdefaulted = true
+      end
     end
 
     # Default kitchen fan

HPXMLtoOpenStudio/resources/hpxml_schematron/EPvalidator.xml

@@ -1303,6 +1303,9 @@
     <sch:rule context='/h:HPXML/h:Building/h:BuildingDetails/h:Systems/h:MechanicalVentilation/h:VentilationFans/h:VentilationFan[h:UsedForWholeBuildingVentilation="true" and h:FanType="central fan integrated supply"]'>
       <sch:assert role='ERROR' test='count(h:AttachedToHVACDistributionSystem) = 1'>Expected 1 element(s) for xpath: AttachedToHVACDistributionSystem</sch:assert>
       <sch:assert role='ERROR' test='count(h:IsSharedSystem[text()="true"]) = 0'>Expected 0 element(s) for xpath: IsSharedSystem[text()="true"]</sch:assert>
+      <sch:assert role='ERROR' test='count(h:extension/h:VentilationOnlyModeAirflowFraction) &lt;= 1'>Expected 0 or 1 element(s) for xpath: extension/VentilationOnlyModeAirflowFraction</sch:assert>
+      <sch:assert role='ERROR' test='number(h:extension/h:VentilationOnlyModeAirflowFraction) &gt;= 0 or not(h:extension/h:VentilationOnlyModeAirflowFraction)'>Expected extension/VentilationOnlyModeAirflowFraction to be greater than or equal to 0</sch:assert>
+      <sch:assert role='ERROR' test='number(h:extension/h:VentilationOnlyModeAirflowFraction) &lt;= 1 or not(h:extension/h:VentilationOnlyModeAirflowFraction)'>Expected extension/VentilationOnlyModeAirflowFraction to be less than or equal to 1</sch:assert>
     </sch:rule>
   </sch:pattern>
 

HPXMLtoOpenStudio/tests/test_defaults.rb

@@ -1788,17 +1788,19 @@ def test_mech_ventilation_fans
     vent_fan.is_shared_system = false
     vent_fan.hours_in_operation = 12.0
     vent_fan.fan_power = 12.5
+    vent_fan.cfis_vent_mode_airflow_fraction = 0.5
     XMLHelper.write_file(hpxml.to_oga, @tmp_hpxml_path)
     hpxml_default = _test_measure()
-    _test_default_mech_vent_values(hpxml_default, false, 12.0, 12.5, 330)
+    _test_default_mech_vent_values(hpxml_default, false, 12.0, 12.5, 330, 0.5)
 
     # Test defaults w/ CFIS
     vent_fan.is_shared_system = nil
     vent_fan.hours_in_operation = nil
     vent_fan.fan_power = nil
+    vent_fan.cfis_vent_mode_airflow_fraction = nil
     XMLHelper.write_file(hpxml.to_oga, @tmp_hpxml_path)
     hpxml_default = _test_measure()
-    _test_default_mech_vent_values(hpxml_default, false, 8.0, 165.0, 330)
+    _test_default_mech_vent_values(hpxml_default, false, 8.0, 165.0, 330, 1.0)
 
     # Test inputs not overridden by defaults w/ ERV
     hpxml = _create_hpxml('base-mechvent-erv.xml')
@@ -3649,13 +3651,19 @@ def _test_default_duct_values(hpxml, supply_locations, return_locations, supply_
     end
   end
 
-  def _test_default_mech_vent_values(hpxml, is_shared_system, hours_in_operation, fan_power, flow_rate)
+  def _test_default_mech_vent_values(hpxml, is_shared_system, hours_in_operation, fan_power, flow_rate,
+                                     cfis_vent_mode_airflow_fraction = nil)
     vent_fan = hpxml.ventilation_fans.select { |f| f.used_for_whole_building_ventilation }[0]
 
     assert_equal(is_shared_system, vent_fan.is_shared_system)
     assert_equal(hours_in_operation, vent_fan.hours_in_operation)
     assert_in_epsilon(fan_power, vent_fan.fan_power, 0.01)
     assert_in_epsilon(flow_rate, vent_fan.rated_flow_rate.to_f + vent_fan.calculated_flow_rate.to_f + vent_fan.tested_flow_rate.to_f + vent_fan.delivered_ventilation.to_f, 0.01)
+    if cfis_vent_mode_airflow_fraction.nil?
+      assert_nil(vent_fan.cfis_vent_mode_airflow_fraction)
+    else
+      assert_equal(cfis_vent_mode_airflow_fraction, vent_fan.cfis_vent_mode_airflow_fraction)
+    end
   end
 
   def _test_default_kitchen_fan_values(hpxml, quantity, flow_rate, hours_in_operation, fan_power, start_hour)

docs/source/workflow_inputs.rst

@@ -1854,13 +1854,18 @@ If an energy recovery ventilator system is specified, additional information is
 
 If a central fan integrated supply system is specified, additional information is entered in ``VentilationFan``.
 
-  ====================================  ======  =====  ===========  ========  =======  ==================================
-  Element                               Type    Units  Constraints  Required  Default  Notes
-  ====================================  ======  =====  ===========  ========  =======  ==================================
-  ``AttachedToHVACDistributionSystem``  idref          See [#]_     Yes                ID of attached distribution system
-  ====================================  ======  =====  ===========  ========  =======  ==================================
+  ================================================  ======  =====  ===========  ========  =======  ==================================
+  Element                                           Type    Units  Constraints  Required  Default  Notes
+  ================================================  ======  =====  ===========  ========  =======  ==================================
+  ``AttachedToHVACDistributionSystem``              idref          See [#]_     Yes                ID of attached distribution system
+  ``extension/VentilationOnlyModeAirflowFraction``  double         0 - 1        No        1.0      Blower airflow rate fraction during ventilation only mode [#]_
+  ================================================  ======  =====  ===========  ========  =======  ==================================
 
   .. [#] HVACDistribution type cannot be HydronicDistribution.
+  .. [#] Blower airflow rate when operating in ventilation only mode (i.e., not heating or cooling mode), as a fraction of the maximum blower airflow rate.
+         This value will depend on whether the blower fan can operate at reduced airflow rates during ventilation only operation.
+         It is used to determine how much conditioned air is recirculated through ducts during ventilation only operation, resulting in additional duct losses.
+         A value of zero will result in no conditioned air recirculation, and thus no additional duct losses.
 
 **Shared System**
 

tasks.rb

@@ -332,6 +332,7 @@ def create_hpxmls
     'base-mechvent-balanced.xml' => 'base.xml',
     'base-mechvent-bath-kitchen-fans.xml' => 'base.xml',
     'base-mechvent-cfis.xml' => 'base.xml',
+    'base-mechvent-cfis-airflow-fraction-zero.xml' => 'base-mechvent-cfis.xml',
     'base-mechvent-cfis-dse.xml' => 'base-hvac-dse.xml',
     'base-mechvent-cfis-evap-cooler-only-ducted.xml' => 'base-hvac-evap-cooler-only-ducted.xml',
     'base-mechvent-erv.xml' => 'base.xml',
@@ -4303,6 +4304,8 @@ def apply_hpxml_modification(hpxml_file, hpxml)
                                sensible_recovery_efficiency: 0.72,
                                fan_power: 7.5,
                                used_for_whole_building_ventilation: true)
+  elsif ['base-mechvent-cfis-airflow-fraction-zero.xml'].include? hpxml_file
+    hpxml.ventilation_fans[0].cfis_vent_mode_airflow_fraction = 0.0
   end
 
   # ---------------- #