ASSIGNMENT 2

(Submission date: 11 May 2015)

1. An adiabatic air compressor is to be powered by a direct-coupled adiabatic steam turbine,

which is also used to drive a generator. Steam enters the turbine at 12.5 MPa and 500oC at

a rate of 25 kg/s and exits at 10 kPa and a quality of 0.92. Air enters the compressor at 98

kPa and 295 K at a rate of 10 kg/s and exits at 1 MPa and 620 K.

(a) Distinguish the operation of a turbine and a compressor by producing the energy

balance equation for each of the device. State your assumptions clearly.

(b) By using the energy balance equations in (a), calculate the net power delivered to the

generator by the turbine.

2. The air flows in a compressed air line is divided into two equal streams by a T-fitting in

the line. The compressed air enters this 2.5 cm diameter fitting at 1.6 MPa and 40oC with

a velocity of 50 m/s. Each outlet has the same diameter as the inlet, and the air at these

outlets has a pressure of 1.4 MPa and a temperature of 36oC. Determine the velocity of the

air at the outlets and the rate of change of flow energy (flow power) across the T-fitting.

Air

compressor

Steam

turbine

1 MPa, 620 K 12.5 MPa, 500oC

10 kPa, x = 0.92 98 kPa, 295 K

1.6 MPa

40 oC

50 m/s

1.4 MPa, 36oC

1.4 MPa, 36oC