Question

Question 3 (a) In a closed system, 0.93 kg of steam at 600 kPa and 200°C undergoes an isothermal and reversible process until 0.76 kg of saturated liquid water is obtained in the system. (i) Determine the entropy change of the mass. (5 marks) (ii) Determine the amount of heat transfer of the system during the process. (3 marks) (b) A two-cylinder two-stroke diesel engine operates on an ideal Diesel cycle, of which compression ratio is 22.5 and cutoff ratio is 1.81. Air is at 97 kPa and 80°C at the end of the heat rejection process. It can be taken that constant specific heats at room temperature can be used. (i) Sketch the cycle on a P-v diagram. (2 marks) (ii) Determine the temperature and the pressure at the beginning of the heat addition process. (4 marks) (iii) Determine the temperature at the beginning of the isentropic expansion process and, hence, or otherwise, the amount of heat transfer from each kg of air during the heat rejection process. (6 marks)

Answer 1

Griven Data :- Po=600 kPa To=200°C &T=T2=200°c Isothermal Process) * Solin 1 O - 1 | T Given process can be represented as shown in fig. Where, state on initial condition ! i saturated Vapauy 2- final state. S-> from steary table: specific entropy at state eo S. = 6.966 KJ /kg. Kº cat state "1" T, = 200°c & P. = 15.5335 bar... + $55,-6-4289 KJ/Kg.K Sig= 4.0996 KT /kg.K Sf = 2.3292 KJ/Kg, K

at state 2 dryness fraction (%): mutme 0.93-0.76 0.93 H₂= 0.1828 Sr tas, at state a specific, entropy (S2):- Sai Sfg, = 2.3292 + (0.1828)(4.0996) - Sz= 3.07859 kJ/Kg.k Change in entropy of the mass? AS = m (Sq-so) = 0.93 (3.07859 – 6.966 AS = - 3.6153 KJ/K

Cü for reversible under (Ts) diagram gives. Heat transferi process area Pri Q = T45) 473*(- 3.6153) 1710.0369 KJ >