Pump and motor sizing (fluids.pump)¶

fluids.pump.
VFD_efficiency
(P, load=1)[source]¶ Returns the efficiency of a Variable Frequency Drive according to [1]. These values are generic, and not standardized as minimum values. Older VFDs often have much worse performance.
Parameters:  P : float
Power, [W]
 load : float, optional
Fraction of motor’s rated electrical capacity being used
Returns:  efficiency : float
VFD efficiency, []
Notes
The use of a VFD does change the characteristics of a pump curve’s efficiency, but this has yet to be quantified. The effect is small. This value should be multiplied by the product of the pump and motor efficiency to determine the overall efficiency.
Efficiency table is in units of hp, so a conversion is performed internally. If load not specified, assumed 1  where maximum efficiency occurs. Table extends down to 3 hp and up to 400 hp; values outside these limits are rounded to the nearest known value. Values between standardized sizes are interpolated linearly. Load values extend down to 0.016.
The table used is for Pulse Width Modulation (PWM) VFDs.
References
[1] (1, 2) GoHz.com. Variable Frequency Drive Efficiency. http://www.variablefrequencydrive.org/vfdefficiency Examples
>>> VFD_efficiency(10*hp) 0.96 >>> VFD_efficiency(100*hp, load=0.2) 0.92

fluids.pump.
CSA_motor_efficiency
(P, closed=False, poles=2, high_efficiency=False)[source]¶ Returns the efficiency of a NEMA motor according to [1]. These values are standards, but are only for fullload operation.
Parameters:  P : float
Power, [W]
 closed : bool, optional
Whether or not the motor is enclosed
 poles : int, optional
The number of poles of the motor
 high_efficiency : bool, optional
Whether or not to look up the highefficiency value
Returns:  efficiency : float
Guaranteed fullload motor efficiency, []
Notes
Criteria for being required to meet the highefficiency standard is:
 Designed for continuous operation
 Operates by threephase induction
 Is a squirrelcage or cage design
 Is NEMA type A, B, or C with T or U frame; or IEC design N or H
 Is designed for singlespeed operation
 Has a nominal voltage of less than 600 V AC
 Has a nominal frequency of 60 Hz or 50/60 Hz
 Has 2, 4, or 6 pole construction
 Is either open or closed
Pretty much every motor is required to meet the lowstandard efficiency table, however.
Several lowefficiency standard high power values were added to allow for easy programming; values are the last listed efficiency in the table.
References
[1] (1, 2) Natural Resources Canada. Electric Motors (1 to 500 HP/0.746 to 375 kW). As modified 20151217. https://www.nrcan.gc.ca/energy/regulationscodesstandards/products/6885 Examples
>>> CSA_motor_efficiency(100*hp) 0.93 >>> CSA_motor_efficiency(100*hp, closed=True, poles=6, high_efficiency=True) 0.95

fluids.pump.
motor_efficiency_underloaded
(P, load=0.5)[source]¶ Returns the efficiency of a motor operating under its design power according to [1].These values are generic; manufacturers usually list 4 points on their product information, but fullscale data is hard to find and not regulated.
Parameters:  P : float
Power, [W]
 load : float, optional
Fraction of motor’s rated electrical capacity being used
Returns:  efficiency : float
Motor efficiency, []
Notes
If the efficiency returned by this function is unattractive, use a VFD. The curves used here are polynomial fits to [1]’s graph, and curves were available for the following motor power ranges: 01 hp, 1.55 hp, 10 hp, 1525 hp, 3060 hp, 75100 hp If above the upper limit of one range, the next value is returned.
References
[1] (1, 2, 3) Washington State Energy Office. EnergyEfficient Electric Motor Selection Handbook. 1993. Examples
>>> motor_efficiency_underloaded(1*hp) 0.8705179600980149 >>> motor_efficiency_underloaded(10.1*hp, .1) 0.6728425932357025

fluids.pump.
Corripio_pump_efficiency
(Q)[source]¶ Estimates pump efficiency using the method in Corripio (1982) as shown in [1] and originally in [2]. Estimation only
\[\eta_P = 0.316 + 0.24015\ln(Q)  0.01199\ln(Q)^2\]Parameters:  Q : float
Volumetric flow rate, [m^3/s]
Returns:  efficiency : float
Pump efficiency, []
Notes
For Centrifugal pumps only. Range is 50 to 5000 GPM, but input variable is in metric. Values above this range and below this range will go negative, although small deviations are acceptable. Example 16.5 in [1].
References
[1] (1, 2, 3) Seider, Warren D., J. D. Seader, and Daniel R. Lewin. Product and Process Design Principles: Synthesis, Analysis, and Evaluation. 2 edition. New York: Wiley, 2003. [2] (1, 2) Corripio, A.B., K.S. Chrien, and L.B. Evans, “Estimate Costs of Centrifugal Pumps and Electric Motors,” Chem. Eng., 89, 115118, February 22 (1982). Examples
>>> Corripio_pump_efficiency(461./15850.323) 0.7058888670951621

fluids.pump.
Corripio_motor_efficiency
(P)[source]¶ Estimates motor efficiency using the method in Corripio (1982) as shown in [1] and originally in [2]. Estimation only.
\[\eta_M = 0.8 + 0.0319\ln(P_B)  0.00182\ln(P_B)^2\]Parameters:  P : float
Power, [W]
Returns:  efficiency : float
Motor efficiency, []
Notes
Example 16.5 in [1].
References
[1] (1, 2, 3) Seider, Warren D., J. D. Seader, and Daniel R. Lewin. Product and Process Design Principles: Synthesis, Analysis, and Evaluation. 2 edition. New York: Wiley, 2003. [2] (1, 2) Corripio, A.B., K.S. Chrien, and L.B. Evans, “Estimate Costs of Centrifugal Pumps and Electric Motors,” Chem. Eng., 89, 115118, February 22 (1982). Examples
>>> Corripio_motor_efficiency(137*745.7) 0.9128920875679222

fluids.pump.
specific_speed
(Q, H, n=3600.0)[source]¶ Returns the specific speed of a pump operating at a specified Q, H, and n.
\[n_S = \frac{n\sqrt{Q}}{H^{0.75}}\]Parameters:  Q : float
Flow rate, [m^3/s]
 H : float
Head generated by the pump, [m]
 n : float, optional
Speed of pump [rpm]
Returns:  nS : float
Specific Speed, [rpm*m^0.75/s^0.5]
Notes
Defined at the BEP, with maximum fitting diameter impeller, at a given rotational speed.
References
[1] (1, 2) HI 1.3 Rotodynamic Centrifugal Pumps for Design and Applications Examples
Example from [1].
>>> specific_speed(0.0402, 100, 3550) 22.50823182748925

fluids.pump.
specific_diameter
(Q, H, D)[source]¶ Returns the specific diameter of a pump operating at a specified Q, H, and D.
\[D_s = \frac{DH^{1/4}}{\sqrt{Q}}\]Parameters:  Q : float
Flow rate, [m^3/s]
 H : float
Head generated by the pump, [m]
 D : float
Pump impeller diameter [m]
Returns:  Ds : float
Specific diameter, [m^0.25/s^0.5]
Notes
Used in certain pump sizing calculations.
References
[1] Green, Don, and Robert Perry. Perry’s Chemical Engineers’ Handbook, Eighth Edition. McGrawHill Professional, 2007. Examples
>>> specific_diameter(Q=0.1, H=10., D=0.1) 0.5623413251903491

fluids.pump.
speed_synchronous
(f, poles=2, phase=3)[source]¶ Returns the synchronous speed of a synchronous motor according to [1].
\[N_s = \frac{120 f \cdot\text{phase}}{\text{poles}}\]Parameters:  f : float
Line frequency, [Hz]
 poles : int, optional
The number of poles of the motor
 phase : int, optional
Line AC phase
Returns:  Ns : float
Speed of synchronous motor, [rpm]
Notes
Synchronous motors have no slip. Large synchronous motors are not selfstarting.
References
[1] (1, 2) All About Circuits. Synchronous Motors. Chapter 13  AC Motors http://www.allaboutcircuits.com/textbook/alternatingcurrent/chpt13/synchronousmotors/ Examples
>>> speed_synchronous(50, poles=12) 1500.0 >>> speed_synchronous(60, phase=1) 3600.0

fluids.pump.
nema_sizes
= [186.42496789556753, 248.5666238607567, 372.84993579113507, 559.2749036867026, 745.6998715822701, 1118.5498073734052, 1491.3997431645403, 2237.0996147468104, 2982.7994863290805, 3728.4993579113507, 4101.349293702486, 5592.749036867026, 7456.998715822701, 11185.498073734052, 14913.997431645403, 18642.496789556753, 22370.996147468104, 29827.994863290805, 37284.99357911351, 44741.99229493621, 55927.49036867026, 74569.98715822701, 93212.48394778377, 111854.98073734052, 130497.47752689727, 149139.97431645403, 186424.96789556753, 223709.96147468104, 260994.95505379455, 298279.94863290805, 335564.94221202156, 372849.93579113507]¶ list: all NEMA motor sizes in increasing order, in Watts.

fluids.pump.
nema_sizes_hp
= [0.25, 0.3333333333333333, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 5.5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 175, 200, 250, 300, 350, 400, 450, 500]¶ list: all NEMA motor sizes in increasing order, in horsepower.

fluids.pump.
motor_round_size
(P)[source]¶ Rounds up the power for a motor to the nearest NEMA standard power. The returned power is always larger or equal to the input power.
Parameters:  P : float
Power, [W]
Returns:  P_actual : float
Actual power, equal to or larger than input [W]
Notes
An exception is raised if the power required is larger than any of the NEMA sizes. Larger motors are available, but are unstandardized.
References
[1] Natural Resources Canada. Electric Motors (1 to 500 HP/0.746 to 375 kW). As modified 20151217. https://www.nrcan.gc.ca/energy/regulationscodesstandards/products/6885 Examples
>>> motor_round_size(1E5) 111854.98073734052

fluids.pump.
current_ideal
(P, V, phase=3, PF=1)[source]¶ Returns the current drawn by a motor of power P operating at voltage V, with line AC of phase phase and power factor PF according to [1].
Singlephase power:
\[I = \frac{P}{V \cdot \text{PF}}\]3phase power:
\[I = \frac{P}{V \cdot \text{PF} \sqrt{3}}\]Parameters:  P : float
Power, [W]
 V : float
Voltage, [V]
 phase : int, optional
Line AC phase, either 1 or 3
 PF : float, optional
Power factor of motor
Returns:  I : float
Power drawn by motor, [A]
Notes
Does not include power used by the motor’s fan, or startor, or internal losses. These are all significant.
References
[1] (1, 2) Electrical Construction, and Maintenance. “Calculating Single and 3Phase Parameters.” April 1, 2008. http://ecmweb.com/basics/calculatingsingleand3phaseparameters. Examples
>>> current_ideal(V=120, P=1E4, PF=1, phase=1) 83.33333333333333