## 1 MECE2320U-THERMODYNAMICS HOMEWORK # 5 Instructor: Dr. Ibrahim Dincer Assignment Date: Thursday, 22 October 2015 Assignment Type: Individual Due Date: Thursday, 29 October 2015 (3.00 pm latest, leave in dropbox 8) 1) As shown in figure, the inlet and outlet conditions of a steam turbine are given. The heat loss from turbine is 35 kJ per kg of steam. a) Show all the state points on T-v diagram b) Write mass and energy balance equations c) Calculate the turbine work 2) As shown in figure, refrigerant R134a enters to a compressor. Write both mass and energy balance equations. Calculate the compressor work and the mass flow rate of refrigerant. 3) As shown in figure, the heat exchanger uses the heat of hot exhaust gases to produce steam. Where, 15% of heat is lost to the surroundings. Exhaust gases enters the heat exchanger at 500°C. Water enters at 15°C as saturated liquid and exit at saturated vapor at 2 MPa. Mass flow rate of water is 0.025 kg/s, and for exhaust gases, it is 0.42 kg/s. The specific heat for exhaust gases is 1.045 kJ/kg K, which can be treated as ideal gas. 1 Turbine 2 ? 1 = 1 ??/? ?1 = 1 ??? ?1 = 300 ℃ ?1 = 40 ?/? ? ??? =? ????? = 35 ??/?? ?2 = 150 ??? ?2 = 0.9 ?2 = 180 ?/? 1 Compressor 2 ???? ???? = 1.3 ?3/??? ?1 = 100 ??? ?1 = −20 ℃ ? ?? =? ? ???? = 3 ?? ?2 = 800 ??? ?2 = 60 ℃ 2 a) Write mass and energy balance equations. b) Calculate the rate of heat transfer to the water. c) Calculate the exhaust gases exit temperature. 4) As shown in figure, two refrigerant R134a streams mix in a mixing chamber. If the mass flow rate of cold stream is twice that of the hot stream. a) Write mass and energy balance equations. b) Calculate the temperature of the mixture at the exit of the mixing chamber c) Calculate the quality at the exit of the mixing chamber 5) As shown in figure, an air conditioning system requires airflow at the main supply duct at a rate of 140 m3/min. The velocity inside circular duct is not to exceed 9 m/s. Assume that the fan converts 85% of electrical energy it consumes into kinetic energy of air. a) Write mass and energy balance equations. b) Calculate the size of electric motor require to drive the fan c) Calculate the diameter of the main duct ?2 = 1 ??? ?2 = 90 ℃ ?1 = 1 ??? ?1 = 30 ℃ ?3 =? ?3 =? 140 ?3/??? 9 ?/? Air Fan

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