Question

ME-311: Thermodynamics I VerSteeg In-Class Example Problem Chapter 6 Example: Entropy Handling A rigid tank is divided into two equal parts by a partition. One part of the tank contains 2.5 kg of compressed water at 400 kPa and 60°C while the other part is evacuated. The partition is now removed, and the water expands to fill the entire tank, Determine: d) The entropy change of water during this process, if the final pressure in the tank is 40 kPa. (k)/K) The entropy change of the surrounding air, assuming the temperature of that air is constant at 25°C (k)/K) The entropy generated (kJ/K) g) e) Given your answer to part (C), what can you conclude about this process? Support your conclusion. h) What is the theoretical maximum pressure possible (i.e. "best case scenario") at the end of the process? (kPa) OP 400 K pa ) H20 MI: 2 Po:40 kfa m2: M,

Answer 1

State 1 P = 400 kPa Ti = Goc u šis w=0.00102 milkg s = 0.831 kJIKOK 4, = h, = 251 KTIKq V = 29, x m = 0.polo 2 X 2.5 2.5SX10" loom State 2 V2 = 2V, = 5.18103 m3 i 0,= 5.1X10 - 2.04x10 m Ikg → P2 = 40 kPa 92 = 1.03 kJ/kgk Ug = 318 kJ/kg d) Entropy change, OS=5,-5, = 2.5(103 -0.831) = 0.4975 KTIK. e) Heat transferred to surroundings, = " (Ug-4.) Q = 2.5(318-251) = 167.5 kJ ossunr = Q = 167.5 f) ssgen - Assystem + Asunt - = 0.562 KJ/K. 254273 = 0.4975 +0.562 = 1.0595 KJ/K. 9) There is no part 'C' (Assuming of) since osgen is tve, the entropy of universe increases which means the process is highly irreversible.