ES 7- THERMODYNAMICS 2 1. Specify whether the steam is wet, dry saturated, or superheated, and find other properties as indicated: a. P=7.8 MPa, y = 15 %. Find: V and h. b. T= 200 deg C, S-6 Kj/kg.K. Find: P and U. c. P=5.8 MPa, t= 500 deg C. Find: V and S. d. P=3.5 MPa, t= 375 deg C. Find: U and h. e. P= 10 MPa, y = 5%. Find: t and V. Where: P = pressure, y = moisture, V-specific volume, h= specific enthalpy, S = specific entropy, U= specific internal energy. 2. A piston-cylinder containing steam at 700 kPa and 250 deg 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 kl/kg; (b)-810 kl/kg; (c)-708.5 ki/kg. (d)-810 kJ/kg. 3. A 1kg steam water mixture at 1.0 MPa is contained in an inflexible tank. Heat is added until the pressure rises to 3.5 MPa and the temperature to 400 deg C. Determine the heat added. (Ans. 1378.7 kl.) 4. A steam engine isentropically expands 5 kg/s of steam from 0.68 MPa, 220deg C. The exhaust is dry and saturated. Determine (a) the work of a nonflow process, (b) the final temperature, (c) the work of a steady flow process. Ans. (a) 629.75 kl/s (b) 133.449 deg C. (c) 823.25 ki/s. 5. Steam at 5 MPa and 400 deg C expands polytropically to 1.0 MPa according to PVC. Determine the work of nonflow and steady flow, the heat transferred, Ah, A.S. Ans. 298.9 kJ/kg, 388.6 kJ/kg.-7.6 kJ/kg.-396.2kl/kg, -0.0127 kJ/kg.K. 6. Wet steam at 1.0 MPa flowing through a pipe is throttled to a pressure of 0.10 MPa. If the throttling temperature is 110 deg C, what is the quality of the steam in the pipe? Ans. 95.95%. 7. In an ideal Rankine cycle, steam is generated at 4.1 MPa and 480 deg C. The condenser is at 32 deg C. Determine (a) the ideal pump work, (b) the cycle thermal efficiency, (c) For an engine with the same end states, determine its thermal efficiency, steam rate, and mean effective pressure. (d) Considering the engine only, assume the brake engine efficiency to be 78%, the generator efficiency 92%, the steam flow rate 163,600 kg/hr, compute the output of the combined unit. Ans. (a) 4.12 kl/kg; (b) 38.66%; (c) 38.73 %, 2.85 kg/kwh, 51.92 kPa; (d) 41,227 kW.