Blue Book Flash Card

181. A student living in a 4 m x 6 m x 6 m dormitory room turns on her 150 watts fan before she

leaves the room on a summer day, hoping that the room will be cooler when she comes back in

the evening. Assuming all the doors and windows are tightly closed and disregarding any heat

transfer through the walls and the windows, determine the temperature in the room when she

comes back 10 hours later. Use specific heat values at room temperature, and assume the room

to be at 100 kPa and 15°C in the morning when she leaves.

A. 28.13°C B. 38.13°C

C. 48.13°C D. 58.13°C

182. A piston-cylinder device whose piston is resting on top of a set of stops initially contains

0.50 kg of helium gas at 100 kPa and 25°C. The mass of the piston is such that 500 kPa of

pressure is required to raise it. How much heat must be transferred to the helium before the

piston starts rising?

A. 1557.13 kJ B. 1657.13 kJ

C. 1757.13 kJ D. 1857.13 kJ

183. In order to cool 1 ton (1000 kg) of water at 20°C in an insulated tank, a person pours 80 kg

of ice at -5°C into the water. Determine the final equilibrium temperature in the tank. The

melting temperature and the heat of fusion of ice at atmospheric pressure are 0°C and 333.7

kJ/kg, respectively.

A. 12.43°C B. 14.43°C

C. 16.43°C D. 18.43°C

184. A fan is powered by 0.5 hp motor and delivers air at a rate of 85 m3

/min. Determine the

highest value for the average velocity of air mobilized by the fan. Take the density of air to be

1.18 kg/m3

.

A. 18.23 m/s B. 21.12 m/s

C. 25.34 m/s D. 32.23 m/s

185. An Ocean-Thermal Energy Conversion power plant generates 10,000 kW using a warm

surface water inlet temperature of 26°C and cold deep-water temperature of 15°C. On the basis

of a 3°C drop in the temperature of the warm water and a 3°C rise in the temperature of the

cold water due to removal and addition of heat, calculate the power required in kW to pump

the cold-deep water to the surface and through the system heat exchanger if the required

pumping pressure increase is 12 kPa. Assume a Carnot cycle efficiency and density of cold water

to be 100 kg/m3

.

A. 108 B. 250

C. 146 D. 160

188. An elastic sphere containing gas at 120 kPa has a diameter of 1.0 m. Heating the sphere

causes it to expand to a diameter of 1.3 m. During the process the pressure is proportional to

the sphere diameter. Calculate the work done by the gas in kJ.

A. 41.8 B. 50.6

C. 87.5 D. 35.4

189. An ideal gas with a molecular weight of 7.1 kg/kg mol is compressed from 600 kPa and 280

K to a final specific volume of 0.5 m3

/kg. During the process the pressure varies according to P =

620 + 150υ + 95 υ

2 where p is in kPa and υ in m3

/kg. Calculate the work of compression in kJ/kg.

A. 32.8 B. 28.7

C. 35.6 D. 33.3

190. A one cubic meter container contains a mixture of gases composed of 0.02 kg-mol of

oxygen and 0.04 kg-mol of helium at a pressure of 220 kPa. What is the temperature of this

ideal gas mixture in Kelvin?

A. 441 B. 350

C. 400 D. 450

191. Methyl alcohol (CH3OH) is burned with 25% excess air. How much unburned oxygen in kg-

moloxygen/kg-molfuel will there be in the products if the combustion is complete?

A. 0.35 B. 0.45

C. 0.37 D. 0.65

192. A 12 DC electrical motor draws a current of 15 amps. How much work in kJ does this motor

produce over a 10-minute period of operation?

A. 108.0 B. 129.6

C. 216.0 D. 318.2

193. A 4 liter (2-liter per revolution at standard pressure and temperature) spark ignition engine

has a compression ratio of 8 and 2200 kJ/kg heat addition by the fluid combustion. Considering

a cold air-standard Otto cycle model, how much power will the engine produce when operating

at 2500 rpm?

A. 166.53 hp B. 73.12 hp

C. 97.4 hp D. 148 hp

194. A simple Rankine cycle produces 40 MW of power, 50 MW of process heated and rejects

50 MW of heat to the surroundings. What is the utilization factor of this cogeneration cycle

neglecting the pump work?

A. 50% B. 60%

C. 64% D. 80%

195. The rate of heat transfer to the surroundings from a person at rest is 400 kJ/hr. Suppose

that the ventilation system fails in an auditorium containing 120 people and assuming that the

energy goes into the air of volume 1500 m3

initially at 300 K and 101 kPa, calculate the rate in

°C /min of air temperature change.

A. 0.81 B. 0.53

C. 0.63 D. 1.0

196. An insulated box containing helium gas falls from a balloon 4.5 km above the earth’s

surface. Calculate the temperature rise in °C of the helium when box hits the ground.

A. 15.2 B. 12.6

C. 25.3 D. 14.1

197. Consider two Carnot heat engines operating in series. The first engine receives heat from

the reservoir at 2400 K and rejects the waste heat to another reservoir at temperature T. The

second engine receives heat by the first one, convert some of it to work, and rejects the rest to a reservoir at 300 K. If thermal efficiencies of both engines are the same, determine the

temperature T.

A. 849 K B. 578 K

C. 763 K D. 978 K

198. An ideal gas mixture consists of 2 kmol of N2 and 6 kmol of CO2. The mass fraction of CO2

is?

A. 0.175 B. 0.250

C. 0.825 D. 0.750

199. An ideal gas mixture consists of 2 kmol of N2 and 6 kmol of CO2. The apparent gas constant

of mixture is?

A. 0.208 B. 0.231

C. 0.531 D. 0.825

200. A Carnot cycle operates between the temperature limits of 300 K and 1500 K, and 

produces 600 kW of net power. The rate of entropy change of the working fluid during heat 

addition process is?

A. 0 B. 0.4

C. 0.5 D. 2.0

186. A plate-type solar energy collector with an absorbing surface covered by a glass plate is to

receive an incident radiation of 800 W/m2

. The glass plate has a reflectivity of 0.12 and atransmissivity of 0.85. The absorbing surface has an absorptivity of 0.90. The area of the

collector is 5 m2

. How much solar energy in watts is absorbed by the collector?

A. 2500 B. 2880

C. 3510 D. 3060

187. A tank contains liquid nitrogen at -190°C is suspended in a vacuum shell by three stainless

steel rods of 0.80 cm in diameter and 3 meters long with a thermal conductivity of 16.3 W/m2

-

°C. If the ambient air outside the vacuum shell is 15°C, calculate the magnitude of the

conductive heat flow in watts along the support rods.

A. 0.168 B. 0.0587

C. 0.182 D. 0.176