13468-9-152P AID: 1825 | 28/11/2014

(a)

Show the four processes of an air-standard cycle on diagram as in Figure (1).

Show the four processes of an air-standard cycle on diagram as in Figure (2).

(b)

Use ideal-gas specific heats of various common gases table, to find the properties of air at room temperature.

For the given air-standard cycle, let , , , , and be the temperature, pressure, specific internal energy, specific enthalpy, and specific volume of air at state respectively.

Express the temperature and pressure relation for the isentropic process 3-4.

Here, the specific heat ratio of air is k.

Substitute 1,300 K for , for , and 1.4 for k to find .

Express the ideal gas relation of air for the process 1-2.

(1)

For process 1-2, volume remains constant, hence and are equal. Rearrange Equation (1), and substitute 300 kPa for , 100 kPa for , and 300 K for to find .

Find the heat input for the air-standard cycle .

Here, the heat added during the process 1-2 is , the heat added during the process 2-3 is , specific heat of air at constant volume is , and specific heat of air at constant pressure is .

Substitute for , for , 900 K for , 300 K for , and 1,300 K for .

Find the heat rejected for the air-standard cycle .

Substitute for , 949.8 K for , and 300 K for .

Find the net work output for the air-standard cycle .

Substitute for , and for .

Hence, the net work output for the air-standard cycle is .

(c)

Find the thermal efficiency of the air-standard cycle .

Substitute for , and for .

Hence, the thermal efficiency of the given air-standard cycle is .