Module: Pump

Included in:
OpenStudio::Model::PumpConstantSpeed, OpenStudio::Model::PumpVariableSpeed
Defined in:
lib/openstudio-standards/standards/Standards.Pump.rb

Overview

A variety of pump calculation methods that are the same regardless of pump type. These methods are available to PumpConstantSpeed, PumpVariableSpeed

Instance Method Summary collapse

Instance Method Details

#brakeHorsepower ⇒ Double

Determines the brake horsepower of the pump based on flow rate, pressure rise, and impeller efficiency.

Returns:

  • (Double) —

    brake horsepower @units horsepower (hp)



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 167

def brakeHorsepower()

  # Get flow rate (whether autosized or hard-sized)
  flow_m3_per_s = 0
  if self.autosizedRatedFlowRate.is_initialized
    flow_m3_per_s = self.autosizedRatedFlowRate.get
  else
    flow_m3_per_s = self.ratedFlowRate.get
  end

  # E+ default impeller efficiency
  #http://bigladdersoftware.com/epx/docs/8-4/engineering-reference/component-sizing.html#pump-sizing
  impeller_eff = 0.78
  
  # Get the pressure rise (Pa)
  pressure_rise_pa = self.ratedPumpHead
  
  # Calculate the pump power (W)
  pump_power_w = pressure_rise_pa * flow_m3_per_s / impeller_eff
  
  # Convert to HP
  pump_power_hp = pump_power_w / 745.7 # 745.7 W/HP
  
  return pump_power_hp

end

#motorHorsepower ⇒ Double

Determines the horsepower of the pump motor, including motor efficiency and pump impeller efficiency.

Returns:

  • (Double) —

    horsepower



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 199

def motorHorsepower()

  # Get the pump power
  pump_power_w = self.pumpPower
  
  # Convert to HP
  pump_hp = pump_power_w / 745.7 # 745.7 W/HP
  
  return pump_hp

end

#pumpPower ⇒ Double

Determines the pump power (W) based on flow rate, pressure rise, and total pump efficiency(impeller eff * motor eff). Uses the E+ default assumption of 0.78 impeller efficiency.

Returns:

  • (Double) —

    pump power @units Watts (W)



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 130

def pumpPower()
  
  # Get flow rate (whether autosized or hard-sized)
  flow_m3_per_s = 0
  if self.autosizedRatedFlowRate.is_initialized
    flow_m3_per_s = self.autosizedRatedFlowRate.get
  else
    flow_m3_per_s = self.ratedFlowRate.get
  end

  # E+ default impeller efficiency
  #http://bigladdersoftware.com/epx/docs/8-4/engineering-reference/component-sizing.html#pump-sizing
  impeller_eff = 0.78

  # Get the motor efficiency
  motor_eff = self.motorEfficiency
  
  # Calculate the total efficiency
  # which includes both motor and
  # impeller efficiency.
  pump_total_eff = impeller_eff * motor_eff
  
  # Get the pressure rise (Pa)
  pressure_rise_pa = self.ratedPumpHead
  
  # Calculate the pump power (W)
  pump_power_w = pressure_rise_pa * flow_m3_per_s / pump_total_eff
  
  return pump_power_w

end

#rated_w_per_gpm ⇒ Double

Determines the rated watts per GPM of the pump

Returns:

  • (Double) —

    rated power consumption per flow @units Watts per GPM (W*min/gal)



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 215

def rated_w_per_gpm()

  # Get design power (whether autosized or hard-sized)
  rated_power_w = 0
  if self.autosizedRatedPowerConsumption.is_initialized
    rated_power_w = self.autosizedRatedPowerConsumption.get
  elsif self.ratedPowerConsumption.is_initialized
    rated_power_w = self.ratedPowerConsumption.get
  else
    OpenStudio::logFree(OpenStudio::Error, "openstudio.standards.Pump", "For #{self.name}, could not find rated pump power consumption, cannot determine w per gpm correctly.")
    return 0.0
  end

  rated_m3_per_s = 0
  if self.autosizedRatedFlowRate.is_initialized
    rated_m3_per_s = self.autosizedRatedFlowRate.get
  elsif self.ratedFlowRate.is_initialized
    rated_m3_per_s = self.ratedFlowRate.get
  else
    OpenStudio::logFree(OpenStudio::Error, "openstudio.standards.Pump", "For #{self.name}, could not find rated pump Flow Rate, cannot determine w per gpm correctly.")
    return 0.0
  end

  rated_w_per_m3s = rated_power_w / rated_m3_per_s

  rated_w_per_gpm = OpenStudio::convert(rated_w_per_m3s, 'W*s/m^3', 'W*min/gal').get

  return rated_w_per_gpm

end

#set_performance_rating_method_pressure_rise_and_motor_efficiency(target_w_per_gpm, template) ⇒ Bool

Set the pressure rise that cooresponds to the target power per flow number, given the standard pump efficiency and the default EnergyPlus pump impeller efficiency of 0.78.

Parameters:

  • target_w_per_gpm (Double) —

    the target power per flow, in W/gpm

Returns:

  • (Bool) —

    return true if successful, false if not

Author:

  • jmarrec



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 14

def set_performance_rating_method_pressure_rise_and_motor_efficiency(target_w_per_gpm, template)

  # Eplus assumes an impeller efficiency of 0.78 to determine the total efficiency
  # http://bigladdersoftware.com/epx/docs/8-4/engineering-reference/component-sizing.html#pump-sizing
  # Rated_Power_Use = Rated_Volume_Flow_Rate * Rated_Pump_Head / Total_Efficiency
  # Rated_Power_Use / Rated_Volume_Flow_Rate =  Rated_Pump_Head / Total_Efficiency
  # Total_Efficiency = Motor_Efficiency * Impeler_Efficiency
  impeller_efficiency = 0.78

  # Get the brake horsepower
  brake_hp = self.brakeHorsepower

  # Find the motor efficiency
  motor_efficiency, nominal_hp = self.standard_minimum_motor_efficiency_and_size(template, brake_hp)

  # Change the motor efficiency
  self.setMotorEfficiency(motor_efficiency)

  total_efficiency = impeller_efficiency * motor_efficiency

  desired_power_per_m3_s = OpenStudio::convert(target_w_per_gpm,'W*min/gal', 'W*s/m^3').get

  pressure_rise_pa = desired_power_per_m3_s * total_efficiency
  pressure_rise_ft_h2O = OpenStudio::convert(pressure_rise_pa,'Pa','ftH_{2}O').get

  # Change pressure rise
  self.setRatedPumpHead(pressure_rise_pa)

  # Report
  OpenStudio::logFree(OpenStudio::Info, 'openstudio.standards.Pump', "For #{self.name}: brake hp = #{brake_hp.round(2)}HP; motor nameplate = #{nominal_hp}HP, motor eff = #{(motor_efficiency*100).round(2)}%; #{target_w_per_gpm.round} W/gpm translates to a pressure rise of #{pressure_rise_pa.round(0)} Pa // #{pressure_rise_ft_h2O.round(2)} ftH2O.")
  
  # Calculate the W/gpm for verification
  calculated_w = self.pumpPower
  
  # Get flow rate (whether autosized or hard-sized)
  flow_m3_per_s = 0
  if self.autosizedRatedFlowRate.is_initialized
    flow_m3_per_s = self.autosizedRatedFlowRate.get
  else
    flow_m3_per_s = self.ratedFlowRate.get
  end
  flow_gpm = OpenStudio.convert(flow_m3_per_s, 'm^3/s', 'gal/min').get
  calculated_w_per_gpm = calculated_w/flow_gpm
  
  OpenStudio::logFree(OpenStudio::Info, 'openstudio.standards.Pump', "For #{self.name}: calculated W/gpm = #{calculated_w_per_gpm.round(1)}.")

  return true

end

#set_standard_minimum_motor_efficiency(template) ⇒ Object 



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 64

def set_standard_minimum_motor_efficiency(template)
  
  # Get the horsepower
  hp = self.horsepower
  
  # Find the motor efficiency
  motor_eff, nominal_hp = standard_minimum_motor_efficiency_and_size(template, hp)

  # Change the motor efficiency
  self.setMotorEfficiency(motor_eff)
  
  OpenStudio::logFree(OpenStudio::Info, 'openstudio.standards.Pump', "For #{self.name}: motor nameplate = #{nominal_hp}HP, motor eff = #{(motor_eff*100).round(2)}%.")
  
  return true    

end

#standard_minimum_motor_efficiency_and_size(template, motor_bhp) ⇒ Double

Determines the minimum pump motor efficiency for a given motor bhp. This should be the total brake horsepower with any desired safety factor already included.

Parameters:

  • motor_bhp (Double) —

    motor brake horsepower (hp)

Returns:

  • (Double) —

    minimum motor efficiency (0.0 to 1.0)



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# File 'lib/openstudio-standards/standards/Standards.Pump.rb', line 87

def standard_minimum_motor_efficiency_and_size(template, motor_bhp)

  motor_eff = 0.85
  nominal_hp = motor_bhp

  # Don't attempt to look up motor efficiency
  # for zero-hp pumps (required for circulation-pump-free
  # service water heating systems).
  return [1.0, 0] if motor_bhp == 0.0

  # Lookup the minimum motor efficiency
  motors = $os_standards["motors"]
  
  # Assuming all pump motors are 4-pole ODP
  search_criteria = {
    "template" => template,
    "number_of_poles" => 4.0,
    "type" => "Enclosed",
  }
  
  motor_properties = self.model.find_object(motors, search_criteria, motor_bhp)
  if motor_properties.nil?
    OpenStudio::logFree(OpenStudio::Error, "openstudio.standards.Pump", "For #{self.name}, could not find motor properties using search criteria: #{search_criteria}, motor_bhp = #{motor_bhp} hp.")
    return [motor_eff, nominal_hp]
  end
 
  motor_eff = motor_properties["nominal_full_load_efficiency"]
  nominal_hp = motor_properties["maximum_capacity"].to_f.round(1)
  # Round to nearest whole HP for niceness
  if nominal_hp >= 2
    nominal_hp = nominal_hp.round
  end
  
  return [motor_eff, nominal_hp]

end