Download ME 3322 Thermodynamics Unit 1 Exam September 5, 2008 - Prof. Marc Smith and more Exams Thermodynamics in PDF only on Docsity! ME 3322 — Thermodynamics Name: Unit 1 Exam Friday, September 5, 2008 - 1 - Instructions This is a closed-book, closed-notes exam. Any necessary equations you may need are listed in the problem itself or on the formula sheet. You will need a calculator. 1. Write the solution for each problem separately. 2. Use only the front side of each sheet of paper. 3. Be organized, clear, and neat. 4. Don’t substitute in values until you need to. 5. Use proper units in all calculations. 6. Be consistent with your sign convention for heat and work from the very beginning. Honor Pledge On my honor, I pledge that I have neither given nor received inappropriate aid in the preparation of this assignment. Signature No. Do not turn in your work. Yes. Turn in your work for grading. For each problem you solved, did you get the correct answer? ME 3322 — Thermodynamics Name: Unit 1 Exam Friday, September 5, 2008 - 2 - Score I-1. A closed system containing 0.5 kg of air undergoes a polytropic process from p1 = 150 kPa and v1 = 0.800 m3/kg to p2 = 600 kPa and v2 = 0.252 m3/kg. Determine the amount of energy transferred from this system by work during this process. Answer: –78 kJ II-2. A gas is contained in a vertical piston-cylinder assembly by a piston with a mass of 200 kg and a face area of 0.01 m2. The atmosphere exerts a pressure of 1 bar on the top of the piston. An electrical resistor transfer energy to the gas at a rate given by , where K = 5 kW/h2RW Kt!! 2. The resistor is energized for 5 minutes and the piston rises by 20 cm. Determine the change in the internal energy of the gas. Assume that the system is well insulated, neglect friction between the piston and the cylinder, and neglect any change in internal energy of the piston or the cylinder. Score gas + _ resistor,WR patm = 1 bar g 200 kgAnswer: 2.88 kJ II-3. A body with a surface area of 0.5 m2 and an emissivity of 0.8 is powered electrically at a rate of 600 W. It is located at the center of a large evacuated chamber whose walls are at 25 °C. At steady state, what is the surface temperature of the body, T Score ? b Answer: 157.4 °C 25 °C body evacuated chamber Tb We
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