solution

A closed system undergoes a process during which there is energy transfer from the system by heat at a constant rate of 10 kW, and the power varies with time according to

where t is time, in h, and is in kW.

(a) What is the time rate of change of system energy at t  0.6 h, in kW?

(b) Determine the change in system energy after 2 h, in kJ.

A gas expands in a piston–cylinder assembly from p1  8.2 bar, V1  0.0136 m3 to p2  3.4 bar in a process during which the relation between pressure and volume is pV1.2  constant. The mass of the gas is 0.183 kg. If the specific internal energy of the gas decreases by 29.8 kJ/kg during the process, determine the heat transfer, in kJ. Kinetic and potential energy effects are negligible.