Answer to Question #296750 in Mechanical Engineering for Harsh

Question

15 kg of air per minute is delivered by a centrifugal compressor. The

inlet and outlet conditions of air are :

C1 = 10 m/s, p1 = 1 bar, v1 = 0.5 m3/kg and C2 = 80 m/s, p2 = 7 bar,

v2 = 0.15 m3/kg. The increase in enthalpy of air passing through the

compressor is 160 kJ/kg, and heat loss to the surroundings is 720

kJ/min.

Assuming that inlet and discharge lines are at the same level, find :

(i) Motor power required to drive the compressor.

(ii) Ratio of inlet to outlet pipe diameter.

Answer 1

A centrifugal compressor is a mechanical device that compresses a fluid with the help of the impeller’s radial acceleration, which is surrounded by the compressor housing. In a centrifugal compressor, the air or gas enters axially in the impeller and it discharges radially. Therefore, it is also called a radial compressor.

Motor power required to drive the compressor:

Motor Efficiency = Cost per KW X . 746 (Power Factor) X Hours of operation X Brake horsepower