# Mechanical Efficiency

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

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) )

### Where:

$$\large{ \eta_m }$$  (Greek symbol eta) = mechanical efficiency

$$\large{ CIR }$$ = cubic inch per revolution

$$\large{ PSI }$$ = gauge pressure in pounds per square inch

$$\large{ PSI }$$ = pressure differential across motor in pounds per square inch

$$\large{ TP }$$ = theoretical pressure

$$\large{ TT }$$ = theoretical torque

$$\large{ \tau }$$  (Greek symbol tau) = torque

### Solve for:

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