Standards.AirTerminalSingleDuctParallelPIUReheat.rb in openstudio-standards-0.2.17.rc1

- old
+ new

@@ -9,13 +9,18 @@
     OpenStudio.logFree(OpenStudio::Debug, 'openstudio.standards.AirTerminalSingleDuctParallelPIUReheat', "Setting PIU fan power for #{air_terminal_single_duct_parallel_piu_reheat.name}.")
 
     # Determine the fan sizing flow rate, min flow rate,
     # and W/cfm
     sec_flow_frac = 0.5
-    min_flow_frac = 0.3
+    min_flow_frac = air_terminal_single_duct_parallel_reheat_piu_minimum_primary_airflow_fraction(air_terminal_single_duct_parallel_piu_reheat)
     fan_efficacy_w_per_cfm = 0.35
 
+    # Set the fan on flow fraction
+    unless air_terminal_single_duct_parallel_piu_reheat_fan_on_flow_fraction.nil?
+      air_terminal_single_duct_parallel_piu_reheat.setFanOnFlowFraction(air_terminal_single_duct_parallel_piu_reheat_fan_on_flow_fraction)
+    end
+
     # Convert efficacy to metric
     # 1 cfm = 0.0004719 m^3/s
     fan_efficacy_w_per_m3_per_s = fan_efficacy_w_per_cfm / 0.0004719
 
     # Get the maximum flow rate through the terminal
@@ -30,11 +35,10 @@
     max_sec_flow_rate_m3_per_s = max_primary_air_flow_rate * sec_flow_frac
     air_terminal_single_duct_parallel_piu_reheat.setMaximumSecondaryAirFlowRate(max_sec_flow_rate_m3_per_s)
     max_sec_flow_rate_cfm = OpenStudio.convert(max_sec_flow_rate_m3_per_s, 'm^3/s', 'ft^3/min').get
 
     # Set the minimum flow fraction
-    # @todo Also compare to min OA requirement
     air_terminal_single_duct_parallel_piu_reheat.setMinimumPrimaryAirFlowFraction(min_flow_frac)
 
     # Get the fan
     fan = air_terminal_single_duct_parallel_piu_reheat.fan.to_FanConstantVolume.get
 
@@ -53,9 +57,53 @@
 
     # Calculate the newly set efficacy
     fan_power_new_w = fan_rise_new_pa * max_sec_flow_rate_m3_per_s / fan_tot_eff
     fan_efficacy_new_w_per_cfm = fan_power_new_w / max_sec_flow_rate_cfm
     OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.AirTerminalSingleDuctParallelPIUReheat', "For #{air_terminal_single_duct_parallel_piu_reheat.name}: fan efficacy set to #{fan_efficacy_new_w_per_cfm.round(2)} W/cfm.")
+
+    return true
+  end
+
+  # Return the fan on flow fraction for a parallel PIU terminal.
+  #
+  # When returning nil, the fan on flow fraction will be set to
+  # be autosize in the EnergyPlus model; OpenStudio assumes that
+  # the default is "autosize". When autosized, this input is set
+  # to be the same as the minimum primary air flow fraction which
+  # means that the secondary fan will be on when the primary air
+  # flow is at the minimum flow fraction.
+  #
+  # @return [Float] returns nil or a float representing the fraction
+  def air_terminal_single_duct_parallel_piu_reheat_fan_on_flow_fraction
+    return nil
+  end
+
+  # Specifies the minimum primary air flow fraction for PFB boxes.
+  #
+  # @param air_terminal_single_duct_parallel_piu_reheat [OpenStudio::Model::AirTerminalSingleDuctParallelPIUReheat] air terminal object
+  # @return [Double] minimum primaru air flow fraction
+  def air_terminal_single_duct_parallel_reheat_piu_minimum_primary_airflow_fraction(air_terminal_single_duct_parallel_piu_reheat)
+    min_primary_airflow_fraction = 0.3
+    return min_primary_airflow_fraction
+  end
+
+  # Set the minimum primary air flow fraction based on OA rate of the space and the template.
+  #
+  # @param air_terminal_single_duct_parallel_piu_reheat [OpenStudio::Model::AirTerminalSingleDuctParallelPIUReheat] the air terminal object
+  # @param zone_min_oa [Double] the zone outdoor air flow rate, in m^3/s.
+  # @return [Bool] returns true if successful, false if not
+  def air_terminal_single_duct_parallel_piu_reheat_apply_minimum_primary_airflow_fraction(air_terminal_single_duct_parallel_piu_reheat, zone_min_oa = nil)
+    # Minimum primary air flow
+    min_primary_airflow_frac = air_terminal_single_duct_parallel_reheat_piu_minimum_primary_airflow_fraction(air_terminal_single_duct_parallel_piu_reheat)
+    air_terminal_single_duct_parallel_piu_reheat.setMinimumPrimaryAirFlowFraction(min_primary_airflow_frac)
+    OpenStudio.logFree(OpenStudio::Debug, 'openstudio.standards.AirTerminalSingleDuctParallelPIUReheat', "For #{air_terminal_single_duct_parallel_piu_reheat.name}: set minimum primary air flow fraction to #{min_primary_airflow_frac}.")
+
+    # Minimum OA flow rate
+    # If specified, set the primary air flow fraction as
+    unless zone_min_oa.nil?
+      min_primary_airflow_frac = [min_primary_airflow_frac, zone_min_oa / air_terminal_single_duct_parallel_piu_reheat.autosizedMaximumPrimaryAirFlowRate.get].max
+      air_terminal_single_duct_parallel_piu_reheat.setMinimumPrimaryAirFlowFraction(min_primary_airflow_frac)
+    end
 
     return true
   end
 end