module Fan
A variety of fan calculation methods that are the same regardless of fan type. These methods are available to FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
Public Instance Methods
Adjust the fan pressure rise to hit the target fan power (W). Keep the fan impeller and motor efficiencies static.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@param target_fan_power [Double] the target fan power in watts @return [Boolean] returns true if successful, false if not
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 43 def fan_adjust_pressure_rise_to_meet_fan_power(fan, target_fan_power) # Get design supply air flow rate (whether autosized or hard-sized) dsn_air_flow_m3_per_s = 0 dsn_air_flow_m3_per_s = if fan.maximumFlowRate.is_initialized fan.maximumFlowRate.get elsif fan.autosizedMaximumFlowRate.is_initialized fan.autosizedMaximumFlowRate.get end # Get the current fan power current_fan_power_w = fan_fanpower(fan) # Get the current pressure rise (Pa) pressure_rise_pa = fan.pressureRise # Get the total fan efficiency fan_total_eff = fan.fanEfficiency # Calculate the new fan pressure rise (Pa) new_pressure_rise_pa = target_fan_power * fan_total_eff / dsn_air_flow_m3_per_s new_pressure_rise_in_h2o = OpenStudio.convert(new_pressure_rise_pa, 'Pa', 'inH_{2}O').get # Set the new pressure rise fan.setPressureRise(new_pressure_rise_pa) # Calculate the new power new_power_w = fan_fanpower(fan) OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.Fan', "For #{fan.name}: pressure rise = #{new_pressure_rise_in_h2o.round(1)} in w.c., power = #{fan_motor_horsepower(fan).round(2)}HP.") return true end
Applies the minimum motor efficiency for this fan based on the motor’s brake horsepower.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@param allowed_bhp [Double] allowable brake horsepower @return [Boolean] returns true if successful, false if not
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 12 def fan_apply_standard_minimum_motor_efficiency(fan, allowed_bhp) # Find the motor efficiency motor_eff, nominal_hp = fan_standard_minimum_motor_efficiency_and_size(fan, allowed_bhp) # Change the motor efficiency # but preserve the existing fan impeller # efficiency. fan_change_motor_efficiency(fan, motor_eff) # Calculate the total motor HP motor_hp = fan_motor_horsepower(fan) # Exception for small fans, including # zone exhaust, fan coil, and fan powered terminals. # In this case, 0.5 HP is used for the lookup. if fan_small_fan?(fan) OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.Fan', "For #{fan.name}: motor eff = #{(motor_eff * 100).round(2)}%; assumed to represent several less than 1 HP motors.") else OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.Fan', "For #{fan.name}: motor nameplate = #{nominal_hp}HP, motor eff = #{(motor_eff * 100).round(2)}%.") end return true end
Determines the baseline fan impeller efficiency based on the specified fan type.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Double] impeller efficiency (0.0 to 1.0) @todo Add fan type to data model and modify this method
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 215 def fan_baseline_impeller_efficiency(fan) # Assume that the fan efficiency is 65% for normal fans # and 55% for small fans (like exhaust fans). # @todo add fan type to fan data model # and infer impeller efficiency from that? # or do we always assume a certain type of # fan impeller for the baseline system? # @todo check COMNET and T24 ACM and PNNL 90.1 doc fan_impeller_eff = 0.65 if fan_small_fan?(fan) fan_impeller_eff = 0.55 end return fan_impeller_eff end
Determines the brake horsepower of the fan based on fan power and fan motor efficiency.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Double] brake horsepower
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 127 def fan_brake_horsepower(fan) # Get the fan motor efficiency existing_motor_eff = 0.7 if fan.to_FanZoneExhaust.empty? existing_motor_eff = fan.motorEfficiency end # Get the fan power (W) fan_power_w = fan_fanpower(fan) # Calculate the brake horsepower (bhp) fan_bhp = fan_power_w * existing_motor_eff / 746 return fan_bhp end
Changes the fan impeller efficiency and also the fan total efficiency at the same time, preserving the motor efficiency.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@param impeller_eff [Double] impeller efficiency (0.0 to 1.0) @return [Boolean] returns true if successful, false if not
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 194 def fan_change_impeller_efficiency(fan, impeller_eff) # Get the existing motor efficiency existing_motor_eff = 0.7 if fan.to_FanZoneExhaust.empty? existing_motor_eff = fan.motorEfficiency end # Calculate the new total efficiency new_total_eff = existing_motor_eff * impeller_eff # Set the revised motor and total fan efficiencies fan.setFanEfficiency(new_total_eff) return true end
Changes the fan motor efficiency and also the fan total efficiency at the same time, preserving the impeller efficiency.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@param motor_eff [Double] motor efficiency (0.0 to 1.0) @return [Boolean] returns true if successful, false if not
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 165 def fan_change_motor_efficiency(fan, motor_eff) # Calculate the existing impeller efficiency existing_motor_eff = 0.7 if fan.to_FanZoneExhaust.empty? existing_motor_eff = fan.motorEfficiency end existing_total_eff = fan.fanEfficiency existing_impeller_eff = existing_total_eff / existing_motor_eff # Calculate the new total efficiency new_total_eff = motor_eff * existing_impeller_eff # Set the revised motor and total fan efficiencies if fan.to_FanZoneExhaust.is_initialized fan.setFanEfficiency(new_total_eff) else fan.setFanEfficiency(new_total_eff) fan.setMotorEfficiency(motor_eff) end return true end
Determines the design fan flow (m3/s)
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Double] design fan flow
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 81 def fan_design_air_flow(fan) # Get design supply air flow rate (whether autosized or hard-sized) dsn_air_flow_m3_per_s = if fan.to_FanZoneExhaust.empty? if fan.maximumFlowRate.is_initialized fan.maximumFlowRate.get elsif fan.autosizedMaximumFlowRate.is_initialized fan.autosizedMaximumFlowRate.get else OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "The maximum flow rate for fan '#{fan.name}' was neither specified nor set to Autosize.") end else if fan.maximumFlowRate.is_initialized fan.maximumFlowRate.get else OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "The maximum flow rate for exhaust fan '#{fan.name}' was not specified.") end end return dsn_air_flow_m3_per_s end
Determines the fan power (W) based on flow rate, pressure rise, and total fan efficiency(impeller eff * motor eff)
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Double] fan power in watts
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 107 def fan_fanpower(fan) # Get the total fan efficiency, # which in E+ includes both motor and # impeller efficiency. fan_total_eff = fan.fanEfficiency # Get the pressure rise (Pa) pressure_rise_pa = fan.pressureRise # Calculate the fan power (W) fan_power_w = pressure_rise_pa * fan_design_air_flow(fan) / fan_total_eff return fan_power_w end
Determines the horsepower of the fan motor, including motor efficiency and fan impeller efficiency.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Double] motor horsepower
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 148 def fan_motor_horsepower(fan) # Get the fan power fan_power_w = fan_fanpower(fan) # Convert to HP fan_hp = fan_power_w / 745.7 # 745.7 W/HP return fan_hp end
Find the actual rated fan power per flow (W/CFM) by querying the sql file
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Double] rated power consumption per flow in watters per cfm, W*min/ft^3
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 341 def fan_rated_w_per_cfm(fan) # Get design power (whether autosized or hard-sized) rated_power_w = fan_fanpower(fan) if fan.maximumFlowRate.is_initialized max_m3_per_s = fan.ratedFlowRate.get elsif fan.autosizedMaximumFlowRate.is_initialized max_m3_per_s = fan.autosizedMaximumFlowRate.get else OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "For #{fan.name}, could not find fan Maximum Flow Rate, cannot determine w per cfm correctly.") return false end rated_w_per_m3s = rated_power_w / max_m3_per_s rated_w_per_cfm = OpenStudio.convert(rated_w_per_m3s, 'W*s/m^3', 'W*min/ft^3').get return rated_w_per_cfm end
Zone exhaust fans, fan coil unit fans, and powered VAV terminal fans all count as small fans and get different impeller efficiencies and motor efficiencies than other fans
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@return [Boolean] returns true if it is a small fan, false if not
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 309 def fan_small_fan?(fan) is_small = false # Exhaust fan if fan.to_FanZoneExhaust.is_initialized is_small = true # Fan coil unit, unit heater, PTAC, PTHP, VRF terminals, WSHP, ERV elsif fan.containingZoneHVACComponent.is_initialized zone_hvac = fan.containingZoneHVACComponent.get if zone_hvac.to_ZoneHVACFourPipeFanCoil.is_initialized is_small = true # elsif zone_hvac.to_ZoneHVACUnitHeater.is_initialized # is_small = true elsif zone_hvac.to_ZoneHVACPackagedTerminalAirConditioner.is_initialized || zone_hvac.to_ZoneHVACPackagedTerminalHeatPump.is_initialized || zone_hvac.to_ZoneHVACTerminalUnitVariableRefrigerantFlow.is_initialized || zone_hvac.to_ZoneHVACWaterToAirHeatPump.is_initialized || zone_hvac.to_ZoneHVACEnergyRecoveryVentilator.is_initialized is_small = true end # Powered VAV terminal elsif fan.containingHVACComponent.is_initialized zone_hvac = fan.containingHVACComponent.get if zone_hvac.to_AirTerminalSingleDuctParallelPIUReheat.is_initialized || zone_hvac.to_AirTerminalSingleDuctSeriesPIUReheat.is_initialized is_small = true end end return is_small end
Determines the minimum fan motor efficiency and nominal size for a given motor bhp. This should be the total brake horsepower with any desired safety factor already included. This method picks the next nominal motor catgory larger than the required brake horsepower, and the efficiency is based on that size. For example, if the bhp = 6.3, the nominal size will be 7.5HP and the efficiency for 90.1-2010 will be 91.7% from Table 10.8B. This method assumes 4-pole, 1800rpm totally-enclosed fan-cooled motors.
@param fan [OpenStudio::Model::StraightComponent] fan object, allowable types:
FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
@param motor_bhp [Double] motor brake horsepower (hp) @return [Array<Double>] minimum motor efficiency (0.0 to 1.0), nominal horsepower
# File lib/openstudio-standards/standards/Standards.Fan.rb, line 244 def fan_standard_minimum_motor_efficiency_and_size(fan, motor_bhp) fan_motor_eff = 0.85 nominal_hp = motor_bhp # Don't attempt to look up motor efficiency # for zero-hp fans, which may occur when there is no # airflow required for a particular system, typically # heated-only spaces with high internal gains # and no OA requirements such as elevator shafts. return [fan_motor_eff, 0] if motor_bhp < 0.0001 # Lookup the minimum motor efficiency motors = standards_data['motors'] # Assuming all fan motors are 4-pole ODP search_criteria = { 'template' => template, 'number_of_poles' => 4.0, 'type' => 'Enclosed' } # Exception for small fans, including # zone exhaust, fan coil, and fan powered terminals. # In this case, use the 0.5 HP for the lookup. if fan_small_fan?(fan) nominal_hp = 0.5 else motor_properties = model_find_object(motors, search_criteria, motor_bhp) if motor_properties.nil? OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "For #{fan.name}, could not find motor properties using search criteria: #{search_criteria}, motor_bhp = #{motor_bhp} hp.") return [fan_motor_eff, nominal_hp] end nominal_hp = motor_properties['maximum_capacity'].to_f.round(1) # If the biggest fan motor size is hit, use the highest category efficiency if nominal_hp > 9998.0 OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.Fan', "For #{fan.name}, there is no greater nominal HP. Use the efficiency of the largest motor category.") nominal_hp = motor_bhp end # Round to nearest whole HP for niceness if nominal_hp >= 2 nominal_hp = nominal_hp.round end end # Get the efficiency based on the nominal horsepower # Add 0.01 hp to avoid search errors. motor_properties = model_find_object(motors, search_criteria, nominal_hp + 0.01) if motor_properties.nil? OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "For #{fan.name}, could not find nominal motor properties using search criteria: #{search_criteria}, motor_hp = #{nominal_hp} hp.") return [fan_motor_eff, nominal_hp] end fan_motor_eff = motor_properties['nominal_full_load_efficiency'] return [fan_motor_eff, nominal_hp] end