Question

An oil of vicosity 7 poise is used for lubrication between shaft and sleeve. The diameter of shaft is 0.6 m and it rotates is 360 rpm. Calculate the power lost in oil for a sleeve length of 160mm. The thickness of oil film is 1.0mm

(a) 25.31 kW

(b) 50.62 kW

(c) 37.97 kW

(d) 12.65 kW

I have been asked this question by my college professor while I was bunking the class.

The query is from Surface Tension, Capillarity, Vapour Pressure and Cavitation in section Properties of Fluids of Fluid Mechanics

Answer 1

The correct answer is (a) 25.31 kW

The explanation is: Power lost=  torque * angular velocity

                                     =  force* radius* angular velocity

                                     =  shear stress * area* radius* angular velocity

                     Shear Stress = viscosity* velocity gradient

                     Power lost= 7916.8*3.142*0.3*0.3*0.3*2*3.142*60

                                      = 25.31 kW.