EX2F08 - ME 336 EXAM 2, NOVEMBER 25, 2008 C. BORGNAKKE, ME...

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ME 336 EXAM 2, NOVEMBER 25, 2008 C. BORGNAKKE, ME Dept. Problem 1 [40 Points] A Brayton cycle has the inlet at 290 K, 100 kPa and uses a compression ratio of 12:1. It has the highest temperature of 1600 K and employs an ideal regenerator. Use cold air properties to solve. a) Find the specific net work b) Find the cycle efficiency c) Find the cycle 2 nd law efficiency. Problem 2 [40 Points] A refrigerator uses R-134a with the state into the condenser as 800 kPa, 40 ° C and the exit of the condenser is saturated liquid at 25 ° C. The mass flow rate is 0.1 kg/s and the low pressure in the cycle is 165 kPa. The condenser has air flowing in at ambient temperature 20 ° C and leaving at 35 ° C. Find the minimum flow rate of air needed. Find the cycle COP Find the condenser second law efficiency. Problem 3 [20 Points] A closed feedwater heater with a trap heats 20 kg/s water from 100 ° C to 250 ° C at 20 MPa. The extraction steam from the turbine enters at 4 MPa, 275 ° C and leaves as saturated liquid. What is the required mass flow rate of the extraction steam?
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EX2F08 - ME 336 EXAM 2, NOVEMBER 25, 2008 C. BORGNAKKE, ME...

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