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Unformatted text preview: MECH 310 Thermodynamics I January 7, 2008 American University of Beirut, Fall 2008 Handout # Quiz 2 Quiz 2 • This is a closed book exam. • You have 90 minutes. • Write your name and section number on both the question and answer sheets. • It is recommended that you read the whole exam before you start solving. Problem 1 (40 points) A rigid metal tank of volume V is connected to the atmosphere through a valve. At- mospheric pressure and temperature are p and T respectively. Initially the tank is evacuated and the valve is closed. The valve is then opened and air flows into the tank. During the first few seconds (from t = 0 to t = t 1 ), air flows rapidly into the tank at a decreasing mass flow rate until the pressure inside the tank increased, from zero to p . Following this fast process is another long process (from t = t 1 to t = t 2 ) during which air flows into the tank at a very small flow rate while the pressure in the tank remains p . The second process ends when the air flow goes to zero. Air is modeled as an ideal gas with specific heat ratio γ = c p /c v , with c p and c v are respectively the constant pressure and constant volume specific heats. (a) Argue why the first process may be modeled as adiabatic. (b) What is the temperature at time t = t 1 ? Express your answer in terms of given quantities. (c) What the amount of heat transfer between the tank and the atmosphere? Express your answer in terms of given quantities....
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- Fall '08