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Unformatted text preview: 650:351 Thermodynamics Doyle Knight Department of Mechanical and Aerospace Engineering Rutgers  The State University of New Jersey New Brunswick, NJ USA Tel: 732 445 4464 Email: doyleknight@gmail.com Office hours: Tuesday and Friday, 9:00 am to 11:30 am and by appointment Midterm Examination Problem No. 1 A cylinder is filled with 1 kg of R12 at 1.5 MPa and 100 C. The refrigerant is cooled to 25 C. Find the heat transfer 1 Q 2 and work done 1 W 2 . Solution The work done is 1 W 2 = integraldisplay 2 1 pdV At p = 1 . 5 MPa, the temperature for saturated vapor is 59.2 C. Since T 1 = 100 C, State 1 is superheated vapor. At T = 25 C, the pressure for saturated vapor is p 2 sat = 651 . 6 kPa. It is therefore evident that p 2 < 1 . 5 MPa (consider p v diagram). Therefore, the piston must hit the stops, and State 2 is saturated liquidvapor or a compressed liquid. 650:351 Thermodynamics Page 1 Midterm Examination The pressure in the R12 remains constant and equal to 1.5 MPa as the piston descends. As theThe pressure in the R12 remains constant and equal to 1....
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 Spring '08
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