MEEN 315 Fall 2016 Section 501 505 Professor Strzelec Homework 12 LAST ONE 100pts Due Wednesday December 7th 2016 at the START of class NO late homework will be accepted You are encouraged to use the problem solving steps and show all of your work Please use this page as a cover sheet Student Name Section 1 5pts A steam power cycle operates between pressures of 2 MPa and 10 kPa with a maximum temperature of 600 C If the insulated turbine has an efficiency of 80 what is the cycle efficiency What is the temperature of the steam at the turbine outlet 2 10pts The turbine in a steam power plant operating between 4MPa and 10 kPa is 84 efficient The steam is reheated at 400kPa to 400 C the maximum temperature in the cycle is 600 C and the cycle mass flow rate of steam is 10 kg s 6pts What is the cycle efficiency 4pts What is the mass flow rate of cooling water through the condenser if the cooling water is only allowed to increase by 10 C as it passes through the condenser 3 10pts A piston cylinder device is used to produce an ideal gas c v 0 6 kJ kg K cp 0 9 kJ kg K R 0 3 kJ kg k k 1 5 power cycle The processes in this cycle are 1 2 isentropic compression with compression ratio of 6 2 3 isothermal expansion back to the initial volume 3 1 isochoric heat rejection back to the initial T 27 C a Show the cycle on P v and T s diagrams b What is the maximum T of the cycle in C c What is the expansion work d What is the compression work e What is the thermal efficiency of the cycle 4 10pts A 4 cyl 4 stroke engine operating on an Otto cycle with CR 11 produces a maximum pressure of 8 kPa At the beginning of compression the air c v 0 823 kJ kg K cp 1 11 kJ kg K is 37 C and 100 kPa Consider both the compression and expansion to be polytropic with n 1 3 Find a The T after expansion b The net work c The thermal efficiency d The MEP e The engine speed for net 50 kW of power 5 10pts A 6 cyl 3 2L 4 stroke engine operating on a Diesel cycle with CR 19 is operating at 1750 rpm At the beginning of the compression cycle the air c v 0 823 kJ kg K cp 1 11 kJ kg K is 67 C and 95 kPa The engine runs on diesel fuel with a heating value of 42 5 MJ kg and AFR of 28 with combustion efficiency of 98 Find a The maximum T in the cycle b The net work c The thermal efficiency d The MEP e The specific fuel consumption in g kW hr 6 5pts A Brayton cycle using air as the working fluid has P R 12 If the cycle operates between 15 C and 600 C with compressor inlet pressure of 90 kPa which will have a greater impact on the back work ratio a compressor with isentropic efficiency of 90 or a turbine with isentropic efficiency of 90 7 5pts A Brayton cycle using air as the working fluid operates with a P R 12 If the air enters the compressor at 13 psia and 20 F and enters the turbine at 1000 F calculate the net work produced by the cycle using constant specific heats at 300 K MEEN 315 Fall 2016 Section 501 505 Professor Strzelec 8 10pts A gas power plant running on a Brayton cycle produces 100 MW of power which it sends to an electric generator The cycle operates between 25 C and 1325 C The low pressure in the cycle is 100 kPa and the compressor PR is 14 What is the turbine power What fraction of the turbine output is required to drive the compressor What is the thermal efficiency of the cycle 9 5pts A kitchen refrigerator uses R134a and 500 W of electrical power to drive its compressor The condenser operates at 40 C and the evaporator operates at 5 C What is the COP for this cycle 10 10 pts An ideal vapor compression refrigeration cycle operates between the pressure limits of 0 12 and 0 9 MPa The working fluid for the cycle is R134a with a flowrate of 0 1 kg s a 2pts Draw the cycle on a T s diagram b 2pts Find the rate at which heat is removed from the cold space c 2pts Determine the power input to the compressor d 2 pts Find the rate of heat rejection e 2pts Calculate the COP 11 10pts The window air conditioner in a dorm room uses R134a as the working fluid The compressor increases the pressure of the working fluid from 200 kPa to 1200 kPa using 1 5 kW of electrical power The air conditioner is basically a heat exchanger that cools atmospheric air from 30 C to 10 C and blows that air into the room Find a 1pt Draw the T s diagram for the cycle b 3pts The mass flow rate of refrigerant c 3pts The heat transfer rate from the low temperature reservoir d 3pts The mass flow rate of the 10 C air 12 10pts Consider a gas refrigeration cycle The 80 efficient compressor takes in helium at 10 C and the boiler delivers helium at 50 C to the 80 efficient turbine The pressure ratio for the cycle is 3 a 2pts Draw the T s diagram for the process b 2pts Determine the minimum temperature in the cycle c 3pts Determine the COP for the cycle d 3pts If the refrigeration rate is 18 kW what is the mass flow rate of the helium