Ai r is compressed by a 30-kW compressor from P1 to P2. The air t emperature i s maintained constant at 25oC during thi s process as a result of heat t ransfer to the surroundings medium at 17oC. Determine the rate of entropy change of the air. State the assumptions made in solving this problem.

The rate of entropy change of the air is - 0.10067kW/K

Explanation:

We'll assume the following

1. It is a steady-flow process;

2. The changes in the kinetic energy and the potential energy are negligible;

3. Lastly, the air is an ideal gas

Energy balance will be required to calculate heat loss;

mh1 + W = mh2 + Q where W = Q.

Also note that the rate of entropy change of the air is calculated by calculating the rate of heat transfer and temperature of the air, as follows;

Rate of Entropy Change = - Q/T

Where Q = 30Kw

T = Temperature of air = 25°C = 298K

Rate = - 30/298

Rate = - 0.100671140939597 KW/K

Rate = - 0.10067kW/K

Hence, the rate of entropy change of the air is - 0.10067kW/K