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Unformatted text preview: MEEN 315—Fall 2010, Makeup Exam 1 Name Section Number I. Multiple choice problems worth 2 pts each. Circle the answer that is the most appropriate or
closest (numerically) to your answer. 1. What is normally found in an engineering abstract (or executive summary)? A. References @Results B. Tables and figures D. Equations 2. Which of the following statements does NOT properly characterize EES:
A. includes thermodynamic property data, including substances not found in the textbook.
B. solves both linear and nonlinear equations.
C. provides access to parametric tables for solving multiple—variable functions.
can determine the values ofx variables when only xl equations are given.
3. A measured property of a certain material changes when the material is cut in half. This
property is
A. intensive C. Dependent Extensive D. independent 4. A measurement of a property of a system as a function of time is not changing. If the system is
not isolated, this means the system A. Is in equilibrium ©Could be in equilibrium B. is not in equilibrium D. Is an open system MEEN 315—Fali 2010, Makeup Exam 1 Name Section Number 5. A first machine has an efficiency of n1 (n1 <1) and a second machine has an efficiency of n2 (n2 <1). The input to the first machine is [1. If the two machines are connected in series such that
the output of the first machine is the input (lg) to the second machine, the output of the second
machine may be described as A I2/ n2 @mmll (1+I2)/(n1+n2) 0 (11+ I2)/(n1n2) ﬂgzgﬁfj 7 9% é, 0,126,211!
723”"; ”Q 712. = 72/61, 6. Suppose a non—adiabatic system experiences an energy gain of 200 Btu during a process. During
the process, which takes 15 seconds, 60 Btu of work are done on the system and a 30 kW heater
adds heat to the system. There is no other work process, but there is another heat transfer process.
Determine the magnitude and sign of the other heat transfer process. A. —166.5 Btu c. +287 Btu
B. +41 Btu .—287 Btu f. 3
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Q2) cud; : ”4257 5K 7. When the state of a system is in the subcooled region, we can approximate its specific volume by using:
A. Vf at the system pressure C. the average of Vf and VE at saturation
Vf at the system temperature D. the quality equation with x<0. MEEN 315—Fall 2010, Makeup Exam 1 Name Section Number 8. Determine the compressibility factor for steam at 11 MPa and 342 °C: f
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0.75 o. 0.96 35; 2.2 6% Meta Q E 9. A piston cylinder arrangement contains one kilogram of saturated helium that undergoes a
constant pressure process from an initial volume of 0.15 m3 to a final volume of 0.25 m3. How much work (use the correct sign according to our convention) is transferred during the process?
The pressure of the helium is 200 kPa. A.10kJ ©20kJ B. 10 kJ D. 20 kJ W: lWV’zM/f} 205w; as; mm f“) M x —————" *3“ 29593 10. A change from a subcooled liquid to a superheated vapor is described by which of the five
diagrams below? (note there are five possible answers) A. Diagram A C. Diagram C E. Diagram E
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ll. Four work—out problems valued as noted. 1. The lower half of a 10 m high cylindrical container is filled with water of density equal to
1000 kg/m3 . The upper half' Is filled with oil that has a specific gravity of 0.85. Determine the
pressure difference between the top and bottom of the cylinderm klpgh w
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2. A hydroelectric dam converts the energy contained in water into electric energy. The water
level in the lake on the upstream side of the dam is 30 ft above the water exiting the turbines. The
upstream lake is a constantlevel lake; that is, its water level above sea level never changes. The
water exits the turbines at 15 ft/sec, and the efficiency with which the turbines and associated
generators turn the water power into 1.8 MW of electrical power is 85%. a. What is the mass flow rate of the water in lbm/sec? (15 pts)
b. if the water is at 60 0F, what is the volumetric flow rate in ft3/min? [If you cannot find the mass flow rate in a, use 5000 lbm/sec] (5 pts) / Pg ‘ _
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3. Air undergoes a polytropic process from an initial state where P1=l4.0 psia and V1=500 in3 to a
final state where P2=60.0 psia and V2=16O ins. Determine: a. The value of the polytropic constant exponent "n" (7 pts)
b. The work done in Btu with the correct sign according to our convention. (7 pts) c. Sketch the process on a PV diagram, show the pressure and volume values on the axes, and
crosshatch the area representing the boundary work. (6 pts) y n y! 3
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4. Three kilograms of water begin at T1: 150°C and an internal energy of U1=7713 kl. The water undergoes a constant pressure process from 1 to 2 until it has a quality xz — 50 %. Subsequently it
undergoes a constant volume process from 2 to 3 until its pressure reaches P3: 75 kPa a. Sketch the processes on a P v diagram showing the vapor dome, and three isotherms and
associated temperatures: 1) the 150 °C isotherm (2 pts) 2) the isotherm through point 2 and associated temperature (2 pts) 3) the isotherm through point 3 and associated temperature. (2 pts)
b. What is the internal energy in kJ at 75 kPa? (7 pts) c. Find the total work interaction in k] with the correct sign. (7 pts) LIL WWW” > o 5,5,4
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