ENGR225Spring2014 - Homework 3 (1)

ENGR225Spring2014 - Homework 3 (1) - ENGR 225 Spring 2014...

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ENGR 225 Spring 2014 Homework #3 due by recitation week of 2/3 1. A piston-cylinder device initially contains 0.07 m3 of nitrogen gas at 130 kPa and 120°C. The nitrogen is now expanded polytropically to a state of 100 kPa and 100°C. Determine the boundary work done during this process. Answer: 1.86 kJ 2. A mass of 5 kg of saturated water vapor at 300 kPa is heated at constant pressure until the temperature reaches 200°C. Calculate the work done by the water during this process. Answer: 165.9 kJ 3. Carbon dioxide contained in a piston-cylinder device is compressed from 0.3 to 0.1 m 3 . During the process, the pressure and volume are related b P= a / v 2 , where a =8 kPa-m 6 . Calculate the work done on the carbon dioxide during this process. Is this work out or work
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Unformatted text preview: in? Answer: -53.3 kJ 4. A well insulated rigid tank contains 2 kg of a saturated liquid-vapor mixture of water at 150 kPa. Initially, three-quarters of the mass is in the liquid phase. An electric resistor placed in the tank is connected to a 110 V source, and a current of 8 A flows through the resistor when the switch is turned on. Determine how long it will take to vaporize all the liquid in the tank. Also, show the process on a T-v diagram with respect to saturation lines. Answer: 60.2 min. 5. Saturated water vapor at 200°C is isothermally condensed to a saturated liquid in a piston-cylinder device. Calculate the heat transfer and work done during this process, in kJ/kg. Answers: 1940 kJ/kg and 196 kJ/kg....
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• Spring '08
• mullen
• Heat, Water vapor, saturated water vapor

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