Practice exam 1

Practice exam 1 - The following heat capacities for air may...

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CHEMICAL ENGINEERING THERMODYNAMICS I (ChBE 2110) Fall 2008, Quiz-1 NAME: February, 2008 1. (30) A pressure gauge on a high pressure steam line reads 80 bar absolute, but temperature measurement is unavailable inside the pipe. A small quantity of steam is bled out through a valve to atmospheric pressure at 1 bar. A thermocouple placed in the bleed stream reads 400°C. What is the temperature inside the high pressure duct? Solution: Choose valve and small container as the system. This is an open system. From equation 2.2 2. (35) The molar volume of air at 1bar and 298.15 K (25°C) is 0.02479 m 3 /mole. One mole air is compressed to 5 bar and 298.15 K by first cooling the air at constant pressure followed by heating at constant volume. Calculate the heat and work requirements and U and H of the air for each path.
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Unformatted text preview: The following heat capacities for air may be assumed independent of temperature: C v = 20.78 and Cp = 29.10 J mol-1 K-1 Assume also for air that P V/ T is a constant, regardless of the changes it undergoes. 3. (35) An adiabatic steady-state turbine is shown as below. The inlet to the turbine is steam at 600°C and 10 bar, with a mass flow rate of 2.5 kg/s. The outlet stream is 400 o C, and the rate of work obtained from the turbine is 1000kJ/second. Assuming the kinetic energy change of the stream is negligible: 1. Is the outlet fluid a single phase of superheated vapor or a mixture of vapor and liquid? 2. What is the pressure of the outlet stream? T 1 =600 o C P 1 =10bar T 2 =400 o C P 2 =?? s kJ W s / 1000-= • High pressure line Valve P=1 bar, T=400 o C thermocouple...
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