申論題

(3) Heat engines are devices for converting thermal energy to work, and their performance are expressed in terms of thermal efficiency, is the heat input per unit mass of the fuid mediut (assumed ideal gas here).

(a)The most effective (also idealized) engine is operated under a Carnot cycle, which consists four processes: (1) Heat addition to the medium at a temperature, T_H, (2) Isentropic expansion of the medium to a lower temperature, T_L; (3) Heat rejection from the medium at temperature T_L; and (4) Isentropic compression of the medium back to temperature TH. Plot the T-s (termperature-entropy) diagram and p-v (pressure-volume) diagram of the process, and derive the thermal efficiency. Discuss the assumptions made in the model. (15%)