mmmu - Energy_and_Power evaluations

In contrast to the liquid rocket in Fig. P3.34, the solid-propellant rocket in Fig. P3.35 is self-contained and has no entrance ducts. Using a control-volume analysis for the conditions shown in Fig. P3.35, compute the rate of mass loss of the propellant, assuming that the exit gas has a molecular weight of 28. <image 1>

(A) -10.0 kg/s

(B) -11.8 kg/s

(C) -12.4 kg/s

Answer with the option's letter from the given choices directly. No punctuation.

The pump-turbine system in Fig. P3.135 draws water from the upper reservoir in the daytime to produce power for a city. At night, it pumps water from lower to upper reservoirs to restore the situation. For a design flow rate of 15,000 gal/min in either direction, the friction head loss is 17 ft. Estimate the power in kW extracted by the turbine. <image 1>

(A) 540 hp

(B) 334 hp

(C) 410 hp

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A pipe of radius R has a fully developed laminarflow of air at P0, T0 with a velocity profile of V = Vc[1 - (r/R)2], where Vc is the velocity on the center-line and r is the radius, as shown in <image 1>. Find the total mass flow rate and the average velocity, both as functions of Vc and R.

(A) $\begin{aligned}V&=\frac{V_c}{3}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^2\\\\\end{aligned}$

(B) $\begin{aligned}V&=\frac{V_c}{2}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^2\\\\\end{aligned}$

(C) $\begin{aligned}V&=\frac{V_c}{2}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^3\\\\\end{aligned}$

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A valve in the cylinder shown in <image 1> has a cross-sectional area of 11 cm2 with a pressure of 735 kPa inside the cylinder and 99 kPa outside.How large a force is needed to open the valve?

(A) F=689.4N

(B) F=660.5N

(C) F=699.6N

(D) F=709.6N

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Our D = 0.625-in-diameter hose is too short, and it is 125 ft from the d=0.375-in-diameter nozzle exit to the garden. If losses are neglected, what is the minimum gage pressure required, inside the hose, to reach the garden? <image 1>

(A) 3000 lbf/ft^2

(B) 3600 lbf/ft^2

(C) 3400 lbf/ft^2

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A gas-turbine power plant operates on the simple Brayton cycle between the pressure limits of 100 and 1600 kPa.The working fluid is air, which enters the compressor at 40°C at a rate of 850 m^3/min and leaves the turbine at 650°C. Using variable specific heats for air and assuming a compressor isentropic efficiency of 85 percent and a turbine isentropic efficiency of 88 percent, determine (1) the net power output and (2) the back work ratio.<image 1>

(A) (1) 6001 kW, (2) 0.436

(B) (1) 6181 kW, (2) 0.536

(C) (1) 6081 kW, (2) 0.536

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What is the capacity of the forward feed evaporator shown in <image 1> in the provided setup?

(A) E1 + E2 + E3

(B) E3

(C) E1

(D) E1 + E2

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The tank in Fig. P2.63 has a 4-cmdiameter plug which will pop out if the hydrostatic force on it reaches 25 N. For 20°C fluids, what will be the reading h on the manometer when this happens? <image 1>

(A) 0.152 m

(B) 2.032 m

(C) 0.362 m

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The pipe flow in Fig. P6.52 is driven by pressurized air in the tank. What gage pressure p_1 is needed to provide a 20°C water flow rate Q = 60 m^3/h? <image 1>

(A) 2.38E6 Pa

(B) 2.61E5 Pa

(C) 1.56E6 Pa

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A blimp cruises at 75 mi/h through sea-level standard air. A differential pressure transducer connected between the nose and the side of the blimp registers 950 Pa. Estimate the absolute pressure at the nose. <image 1>

(A) 110,000 Pa

(B) 102,000 Pa

(C) 98,000 Pa

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The main water line into a tall building has a pressure of 600 kPa at 5 m below ground level, as shown in<image 1>. A pump brings the pressure up so thatnthe water can be delivered at 200 kPa at the top floor 100 m above ground level. Assume a flow rate of 10 kg/s liquid water at 10°C and neglect any difference in kinetic energy and internal energy u. Find the pump work.

The jet engine in Fig. P3.50 admits air at 20°C and 1 atm at (1), where A_1 = 0.5 m^2 and V_1 = 250 m/s. The fuel-air ratio is 1:30. The air leaves section (2) at 1 atm, V_2 = 900 m/s, and A_2 = 0.4 m^2. Compute the test stand support reaction R_x needed. <image 1>

(A) 99,000 N

(B) 102,000 N

(C) 121,000 N

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A room is kept at 25°C by a vapor-compressionrefrigeration cycle with R-134a as the refrigerant. Heat is rejected to cooling water that enters the condenser at 20°C at a rate of 0.13 kg/s and leaves at 28°C. The refrigerant enters the condenser at 1.2 MPa and 50°C and leave as a saturated liquid. If the compressor consumes 1.9 kW of power, determine the exergy destruction in the condenser. Take T0 = 20°C and $c_{p,water}$ = 4.18 kJ/kg⋅°C<image 1>

(A) 0.1 kW

(B) 0.2 kW

(C) 0.3 kW

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Water from a storm drain flows over an outfall onto a porous bed which absorbs the water at a uniform vertical velocity of 8 mm/s, as shown in Fig. P3.19. The system is 5 m deep into the paper. Find the length L of bed which will completely absorb the storm water. <image 1>

(A) 50 m

(B) 70 m

(C) 90 m

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Refrigerant-134a enters the condenser of a residential heat pump at 800 kPa and 35°C at a rate of 0.018 kg/s and leaves at 800 kPa as a saturated liquid. If the compressor consumes 1.2 kW of power, determine the COP of the heat pump.<image 1>

(A) 2.64

(B) 2.54

(C) 2.44

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In Fig. P6.115 all pipes are 8-cm-diameter cast iron. Determine the flow rate from reservoir (1) if valve C is open, with Kvalve = 0.5. <image 1>

(A) 0.0174 m^3/s

(B) 0.0126 m^3/s

(C) 0.0152 m^3/s

Answer with the option's letter from the given choices directly. No punctuation.

In Fig. P2.13 the 20°C water and gasoline are open to the atmosphere and are at the same elevation. What is the height h in the third liquid? <image 1>

(A) 5.69 m

(B) 2.37 m

(C) 1.52 m

Answer with the option's letter from the given choices directly. No punctuation.

A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at230°C by rejecting its waste heat to cooling water that enters the condenser at 18°C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 65°C and leaves at 42°C. The inlet state of the compressor is 60 kPa and 234°C and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine the quality of the refrigerant at the evaporator inlet.<image 1>

(A) q=0.28

(B) q=0.38

(C) q=0.48

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A 40-ft^3 adiabatic container is initially evacuated. The supply line contains air that is maintained at 150 psia and 90°F. The valve is opened until the pressure in the container is the same as the pressure in the supply line. Determine the work potential of the air in this container when it is filled. Take T0 = 80°F.<image 1>

(A) W=817Btu

(B) W=917Btu

(C) W=1017Btu

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An ideal gas is taken from state 1 to state 2 and then to state 3. <image 1>If the process 1-2 is adiabatic and 2-3 is isothermal, what is a true statement about the change in temperature and heat transferred during 1-2?

(A) $\Delta$T > 0, Q > 0

(B) $\Delta$T < 0, Q = 0

(C) $\Delta$T = 0, Q = 0

(D) $\Delta$T > 0, Q < 0

(E) $\Delta$T = 0, Q < 0

Answer with the option's letter from the given choices directly. No punctuation.