Mechanical Efficiency

Mechanical efficiency, abbreviated as \( \eta_m \)  (Greek symbol eta), a dimensionless number, is the ratio of theoretical power the pump needs to operate to the actual power delivered to the pump itself.

 

Mechanical Efficiency Formulas

\(\large{ \eta_m = \frac{ PSI \; 100 }{ TT } }\)	(motor (pressure differential PSI) )
\(\large{ \eta_m = \frac{ PSI \; 100 }{ TP } }\)	(pump (gauge pressure PSI) )
\(\large{ \eta_m = \frac{ P_a }{ P_m } }\)	(DC generator)

Where:

Units	English	Metric
\(\large{ \eta_m }\)  (Greek symbol eta) = mechanical efficiency	\(\large{dimensionless}\)
\(\large{ CIR }\) = cubic inch per revolution	\(\large{\frac{in^3}{rev}}\)	\(\large{\frac{mm^3}{rev}}\)
\(\large{ PSI }\) = gauge pressure in pounds per square inch	\(\large{\frac{lbf}{in^2}}\)	\(\large{Pa}\)
\(\large{ P_m }\) = mechanical input power	\(\large{\frac{ft-lbf}{sec}}\)	\(\large{W}\)
\(\large{ P_a }\) = converted power in armature	\(\large{\frac{ft-lbf}{sec}}\)	\(\large{W}\)
\(\large{ PSI }\) = pressure differential across motor in pounds per square inch	\(\large{\frac{lbf}{in^2}}\)	\(\large{Pa}\)
\(\large{ TP }\) = theoretical pressure	\(\large{\frac{lbf}{in^2}}\)	\(\large{Pa}\)
\(\large{ TT }\) = theoretical torque	\(\large{lbf-ft}\)	\(\large{N-m}\)
\(\large{ \tau }\)  (Greek symbol tau) = torque	\(\large{lbf-ft}\)	\(\large{N-m}\)

Solve for:

\(\large{ TT = \frac{ CIR \; PSI }{ 6.28 } }\)	(motor)
\(\large{ TP = \frac{ \tau \; 6.28 }{ CIR } }\)	(pump)