Module: Fan
- Included in:
- OpenStudio::Model::FanConstantVolume, OpenStudio::Model::FanOnOff, OpenStudio::Model::FanVariableVolume, OpenStudio::Model::FanZoneExhaust
- Defined in:
- lib/openstudio-standards/standards/Standards.Fan.rb
Overview
A variety of fan calculation methods that are the same regardless of fan type. These methods are available to FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust
Instance Method Summary collapse
-
#adjust_pressure_rise_to_meet_fan_power(target_fan_power) ⇒ Bool
Adjust the fan pressure rise to hit the target fan power (W).
- #apply_standard_minimum_motor_efficiency(template, allowed_bhp) ⇒ Object
-
#baseline_impeller_efficiency(template) ⇒ Double
Determines the baseline fan impeller efficiency based on the specified fan type.
-
#brake_horsepower ⇒ Double
Determines the brake horsepower of the fan based on fan power and fan motor efficiency.
-
#change_impeller_efficiency(impeller_eff) ⇒ Object
Changes the fan impeller efficiency and also the fan total efficiency at the same time, preserving the motor efficiency.
-
#change_motor_efficiency(motor_eff) ⇒ Object
Changes the fan motor efficiency and also the fan total efficiency at the same time, preserving the impeller efficiency.
-
#fan_power ⇒ Double
Determines the fan power (W) based on flow rate, pressure rise, and total fan efficiency(impeller eff * motor eff).
-
#motor_horsepower ⇒ Double
Determines the horsepower of the fan motor, including motor efficiency and fan impeller efficiency.
-
#rated_w_per_cfm ⇒ Double
Find the actual rated fan power per flow (W/CFM) by querying the sql file.
-
#small_fan? ⇒ Bool
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.
-
#standard_minimum_motor_efficiency_and_size(template, motor_bhp) ⇒ Array<Double>
Determines the minimum fan motor efficiency and nominal size for a given motor bhp.
Instance Method Details
#adjust_pressure_rise_to_meet_fan_power(target_fan_power) ⇒ Bool
Adjust the fan pressure rise to hit the target fan power (W). Keep the fan impeller and motor efficiencies static.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 34 def adjust_pressure_rise_to_meet_fan_power(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 autosizedMaximumFlowRate.is_initialized autosizedMaximumFlowRate.get else maximumFlowRate.get end # Get the current fan power current_fan_power_w = fan_power # Get the current pressure rise (Pa) pressure_rise_pa = pressureRise # Get the total fan efficiency fan_total_eff = 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 setPressureRise(new_pressure_rise_pa) # Calculate the new power new_power_w = fan_power OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.Fan', "For #{name}: pressure rise = #{new_pressure_rise_in_h2o.round(1)} in w.c., power = #{motor_horsepower.round(2)}HP.") return true end |
#apply_standard_minimum_motor_efficiency(template, allowed_bhp) ⇒ Object
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 5 def apply_standard_minimum_motor_efficiency(template, allowed_bhp) # Find the motor efficiency motor_eff, nominal_hp = standard_minimum_motor_efficiency_and_size(template, allowed_bhp) # Change the motor efficiency # but preserve the existing fan impeller # efficiency. change_motor_efficiency(motor_eff) # Calculate the total motor HP motor_hp = motor_horsepower # 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 small_fan? OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.Fan', "For #{name}: motor eff = #{(motor_eff * 100).round(2)}%; assumed to represent several < 1 HP motors.") else OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.Fan', "For #{name}: motor nameplate = #{nominal_hp}HP, motor eff = #{(motor_eff * 100).round(2)}%.") end return true end |
#baseline_impeller_efficiency(template) ⇒ Double
Add fan type to data model and modify this method
Determines the baseline fan impeller efficiency based on the specified fan type.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 183 def baseline_impeller_efficiency(template) # 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 small_fan? && template != 'NECB 2011' fan_impeller_eff = 0.55 end return fan_impeller_eff end |
#brake_horsepower ⇒ Double
Determines the brake horsepower of the fan based on fan power and fan motor efficiency.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 104 def brake_horsepower # Get the fan motor efficiency existing_motor_eff = 0.7 if to_FanZoneExhaust.empty? existing_motor_eff = motorEfficiency end # Get the fan power (W) fan_power_w = fan_power # Calculate the brake horsepower (bhp) fan_bhp = fan_power_w * existing_motor_eff / 746 return fan_bhp end |
#change_impeller_efficiency(impeller_eff) ⇒ Object
Changes the fan impeller efficiency and also the fan total efficiency at the same time, preserving the motor efficiency.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 164 def change_impeller_efficiency(impeller_eff) # Get the existing motor efficiency existing_motor_eff = 0.7 if to_FanZoneExhaust.empty? existing_motor_eff = motorEfficiency end # Calculate the new total efficiency new_total_eff = existing_motor_eff * impeller_eff # Set the revised motor and total fan efficiencies setFanEfficiency(new_total_eff) end |
#change_motor_efficiency(motor_eff) ⇒ Object
Changes the fan motor efficiency and also the fan total efficiency at the same time, preserving the impeller efficiency.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 139 def change_motor_efficiency(motor_eff) # Calculate the existing impeller efficiency existing_motor_eff = 0.7 if to_FanZoneExhaust.empty? existing_motor_eff = motorEfficiency end existing_total_eff = 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 to_FanZoneExhaust.is_initialized setFanEfficiency(new_total_eff) else setFanEfficiency(new_total_eff) setMotorEfficiency(motor_eff) end end |
#fan_power ⇒ Double
Determines the fan power (W) based on flow rate, pressure rise, and total fan efficiency(impeller eff * motor eff)
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 72 def 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 to_FanZoneExhaust.empty? if maximumFlowRate.is_initialized maximumFlowRate.get else autosizedMaximumFlowRate.get end else maximumFlowRate.get end # Get the total fan efficiency, # which in E+ includes both motor and # impeller efficiency. fan_total_eff = fanEfficiency # Get the pressure rise (Pa) pressure_rise_pa = pressureRise # Calculate the fan power (W) fan_power_w = pressure_rise_pa * dsn_air_flow_m3_per_s / fan_total_eff return fan_power_w end |
#motor_horsepower ⇒ Double
Determines the horsepower of the fan motor, including motor efficiency and fan impeller efficiency.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 125 def motor_horsepower # Get the fan power fan_power_w = fan_power # Convert to HP fan_hp = fan_power_w / 745.7 # 745.7 W/HP return fan_hp end |
#rated_w_per_cfm ⇒ Double
Find the actual rated fan power per flow (W/CFM) by querying the sql file
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 338 def rated_w_per_cfm # Get design power (whether autosized or hard-sized) rated_power_w = model.getAutosizedValueFromEquipmentSummary(self, 'Fans', 'Rated Electric Power', 'W') if rated_power_w.is_initialized rated_power_w = rated_power_w.get else rated_power_w = fan_power OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.Pump', "For #{name}, could not find rated fan power from Equipment Summary. Will calculate it based on current pressure rise and total fan efficiency") end if autosizedMaximumFlowRate.is_initialized max_m3_per_s = autosizedMaximumFlowRate.get elsif maximumFlowRate.is_initialized max_m3_per_s = ratedFlowRate.get else OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Pump', "For #{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_gpm = OpenStudio.convert(rated_w_per_m3s, 'W*s/m^3', 'W*min/ft^3').get return rated_w_per_gpm end |
#small_fan? ⇒ Bool
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
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 304 def small_fan? is_small = false # Exhaust fan if to_FanZoneExhaust.is_initialized is_small = true # Fan coil unit, unit heater, PTAC, PTHP elsif containingZoneHVACComponent.is_initialized zone_hvac = 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 is_small = true elsif zone_hvac.to_ZoneHVACPackagedTerminalHeatPump.is_initialized is_small = true end # Powered VAV terminal elsif containingHVACComponent.is_initialized zone_hvac = containingHVACComponent.get if zone_hvac.to_AirTerminalSingleDuctParallelPIUReheat.is_initialized || zone_hvac.to_AirTerminalSingleDuctSeriesPIUReheat.is_initialized is_small = true end end return is_small end |
#standard_minimum_motor_efficiency_and_size(template, motor_bhp) ⇒ Array<Double>
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.
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# File 'lib/openstudio-standards/standards/Standards.Fan.rb', line 211 def standard_minimum_motor_efficiency_and_size(template, 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 == 0.0 # Lookup the minimum motor efficiency motors = $os_standards['motors'] # Assuming all fan motors are 4-pole ODP template_mod = template.dup if template == 'NECB 2011' if self.class.name == 'OpenStudio::Model::FanConstantVolume' template_mod += '-CONSTANT' elsif self.class.name == 'OpenStudio::Model::FanVariableVolume' template_mod += '-VARIABLE' # 0.909 corrects for 10% over sizing implemented upstream # 0.7457 is to convert from bhp to kW fan_power_kw = 0.909 * 0.7457 * motor_bhp power_vs_flow_curve_name = if fan_power_kw >= 25.0 'VarVolFan-FCInletVanes-NECB2011-FPLR' elsif fan_power_kw >= 7.5 && fan_power_kw < 25 'VarVolFan-AFBIInletVanes-NECB2011-FPLR' else 'VarVolFan-AFBIFanCurve-NECB2011-FPLR' end power_vs_flow_curve = model.add_curve(power_vs_flow_curve_name) setFanPowerMinimumFlowRateInputMethod('Fraction') setFanPowerCoefficient5(0.0) setFanPowerMinimumFlowFraction(power_vs_flow_curve.minimumValueofx) setFanPowerCoefficient1(power_vs_flow_curve.coefficient1Constant) setFanPowerCoefficient2(power_vs_flow_curve.coefficient2x) setFanPowerCoefficient3(power_vs_flow_curve.coefficient3xPOW2) setFanPowerCoefficient4(power_vs_flow_curve.coefficient4xPOW3) else raise("") end end search_criteria = { 'template' => template_mod, '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 small_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 #{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 == 9999.0 OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.Fan', "For #{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 #{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 |