ME 200 Fall 2xxx Final Exam NAME:______________________________________ PUID:_______________________________________ Circle your section: aaa bbbb cccc dddd eeee 7:30AM 10:30AM 1:30PM 3:30PM 4:30PM Instructions: This is a closed book/note exam. You may use a calculator. You must start from the most basic form of the equations and simplify accordingly to receive full credit. Show all your work! Keep your eyes on your own paper. If you are caught cheating you will get a zero for the exam and your name will be turned over to the Dean of Students. Score: PROBLEM TOTAL POSSIBLE YOUR SCORE 1 50 2 25 3 25 4 25 5 25 TOTAL 150
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ME 200 Fall 2xxx
Final Exam NAME:______________________________________ PUID:_______________________________________ Circle your section: aaa bbbb cccc dddd eeee 7:30AM 10:30AM 1:30PM 3:30PM 4:30PM Instructions: This is a closed book/note exam. You may use a calculator. You must start from the most basic form of the equations and simplify accordingly to receive full credit. Show all your work! Keep your eyes on your own paper. If you are caught cheating you will get a zero for the exam and your name will be turned over to the Dean of Students. Score:
PROBLEM TOTAL POSSIBLE
YOUR SCORE
1 50
2 25
3 25
4 25
5 25
TOTAL 150
1 Short Questions a) Score 2 points each by entering T for True and F for false in the boxes in front of
each of the ten statements T The force exerted on the wall of an evacuated tank at 5 feet in a diving pool equals half the force exerted on the wall at 10 feet from the surface of water in the same pool.
Two degrees (Celsius) above normal body temperature measured in Europe is more serious than 2 degrees (Fahrenheit) above normal body temperature measured in the U. S. A bicyclist travelling a distance of 5 miles on a flat terrain at 10 miles/hour expends as much energy as she would have travelling the same distance at 20 miles/hour.
Routine processes require that a HVAC unit transfer 20 kW of heat from a perfectly insulated home maintained at 70 F to the surroundings at an average temperature of 80 F. The HVAC unit consumes less than 1 kW power. The quality of a liquid-vapor mixture is defined as the mass of the liquid divided by the mass of the mixture. The quality of a liquid-vapor mixture is defined as the mass of the liquid divided by the mass of the mixture. The entropy of air at 20 C heated to 40 C increases by 0.07 kJ/kg-K in a constant pressure heating process. The second law of thermodynamics requires that entropy of a system must always increase. The second law of thermodynamics also requires that the entropy of a system plus the entropy of the surroundings can increase or decrease.
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Known: A Rankine cycle operates with steam as the working fluid. The boiler and condenser
pressures are specified, and the mass flow rate is given.
Find: Determine the output of the turbine; the power input to the pump; the thermal efficiency of
the plant.
Sketch:
Assumptions:
(1) Each component of the cycle is analyzed as a control volume at steady state
(2) All processes of the working fluid are internally reversible
(3) The turbine and pump operate adiabatically
(4) Kinetic and potential energy effects are negligible
Analysis:
From the table, at pressure 60 bar, the temperature of saturated liquid-vapor mixture is 275.6 oC;
at pressure 0.06 bar, the temperature of saturated liquid-vapor mixture is 36.16 oC.
So T1=(275.6+100) oC=375.6
oC, T3=36.16
oC.
State 1: T1=375.6 oC, p1=60 bar, by interpolation,
60 bar
0.06 bar
h1=3112.5 kJ/kg, s1=6.4383 k J / k g K
State 2: 2 1
6 .4 3 8 3 /s s kJ kg K , which is greater than 2 f
s and smaller than 2 g
s , so state 2
is in mixture state. T2=36.16 oC.p2=0.06 bar, by interpolation,