mech3020-s11-hw01

mech3020-s11-hw01 - (b) Calculate the maximum temperature...

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MECH 3020 Thermodynamics II: 01/12/11 Homework: Due 1/17 1. An air–standard cycle with variable specific heats is executed in a closed system and is composed of the following four processes: 1–2 Isentropic compression from 100 kPa, 27 C to 800 kPa. 2–3 v = constant heat addition to 1800 K 3–4 Isentropic expansion to 100 kPa 4–1 P = constant heat rejection to the initial state. (a) Show the cycle on P - v and T - s diagrams. (b) Calculate the net work per unit mass. (c) Determine the thermal efficiency. 2. An air–standard cycle is executed in a closed system and is composed of the following four processes: 1–2 Isentropic compression from 100 kPa, 27 C to 1 MPa 2–3 P = constant heat addition in the amount of 2800 kJ/kg 3–4 v = constant heat rejection to 100 kPa 4–1 P = constant heat rejection to the initial state (a) Show the cycle on P - v and T - s diagrams.
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Unformatted text preview: (b) Calculate the maximum temperature of the cycle. (c) Determine the thermal eciency. Assume constant specic heats at room temperature. Answers: 3360 K, 21%. 3. Consider a Carnot cycle executed in a closed system of 0.003 kg air. The temperature limits of the cycle are 300 K and 900 K, and the minimum and maximum pressures in the cycle are 20 and 2000 kPa. Assuming constant specic heats, determine the net work output per cycle. 4. An ideal gas Carnot cycle uses air as the working uid and receives heat from 1027 C. The cycle operates at 1500 cycles/minute, and has a compression ratio of 12. Determine the heat rejection temperature, the thermal eciency, and the amount of hightemperature heat input, per cycle, required for a power output of 500 kW. Answers: 481 K, 63%, 31.8 kJ. 1...
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