A piston-cylinder containing steam at 700 kPa and 250°C undergoes a constant pressure process until the quality is 70%. Determine per kilogram (a) the work done, (b) the heat transferred, (c) the change of internal energy, and (d) the change of enthalpy.
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Chapter 2
1. A piston-cylinder containing steam at 700 kPa and 250°C undergoes a constant pressure process until the quality is 70%. Determine per kilogram (a) the work done, (b) the heat transferred, (c) the change of internal energy, and (d) the change of enthalpy.
Ans. (a) -101.4 kJ/kg; (b)-810 kJ/kg; (c)-708.5 kJ/kg; (d) -810 kJ/kg
2. Steam at 3.1 MPa and with 74.28°C SH rejects 1973.36 kJ per kg of steam heat at constant pressure, determine (a) the final temperature and (b) the change in specific entropy.
Ans. (a) 235.7°C; (b) -3.8572 kJ/kg•K
3. With 3% moisture, 2.5 kg of steam has an enthalpy of 6600 kJ. It is heated at constant pressure to a final condition of 80° superheat. Find (a) the pressure of the process and (b) the quantity of heat received by the steam.
Ans. (a) 0.22 MPa (b) 575 kJ.
4. Five kg of water vapor are contained at 150 kPa and 90 percent quality in a suitable enclosure. Calculate the heat which must be added in order to just produce a saturated vapor. What will the pressure be at the end of the heating process?
Ans. 1045.5 kJ, 168 kPa.
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