Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Chapter 1, Problem 1.50P
A steam pipe 200 mm in diameter passes through a large basement room. The temperature of the pipe wall is 500°C, while that of the ambient air in the room is 20°C. Determine the heat transfer rate by convection and radiation per unit length of steam pipe if the emissivity of the pipe surface is 0.8 and the natural convection heat transfer coefficient has been determined to be 10
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(b)
A transistor with a height of 0.4 cm and a diameter of 0.6 cm is mounted on a circuit board
as shown in Figure 3. The transistor is cooled by air flowing over it with an average heat
transfer coefficient of 30 W/m².K. If the air temperature is 55°C and the transistor case
temperature is not to exceed 70°C, determine the amount of power this transistor can
dissipate safely. Disregard any heat transfer from the transistor base.
Air
55°C
Power
transistor 0.6 cm
T, ≤ 70°C
-0.4 c
0.4 cm-
Figure 3
Exhaust gases from a manufacturing plant are being discharged through a 10-m tall exhaust stack with outer diameter of 1
m wall thickness of 0.2 m, and thermal conductivity of 40 W/m-K. The exhaust gases are discharged at a rate of 1.2 kg/s
while temperature drop between inlet and exit of the exhaust stack is 30°C, and the constant pressure specific heat of the
exhaust gases is 1600 J/kg-K. On a particular day, the outer surface of the exhaust stack experiences radiation with the
surrounding at 27°C, and convection with the ambient air at 27°C also, with an average convection heat transfer coefficient
of 8 W/m2K. Solar radiation is incident on the exhaust stack outer surface at a rate of 150 W/m2, and both the emissivity
and solar absorptivity of the outer surface are 0.9.
Exhaust
stack wall
A-40 W/mK
And
m
Exhaust
gases
Exhaust
stack
a, -8=0.9
Air, 27°C
A-8 W/m²K
T-T-30°C
K
Manufacturing
plant
Determine the inner surface temperature of the exhaust stack (up to 1 decimal place).
The…
A person stands in a breezy room whose temperature is 20 °C. The emissivity of
the person is 0.35. Determine the total rate of heat transfer from this person if the
exposed surface area and the average surface temperature of the person are 1.6
m2 and 29 °C respectively. Take the convection heat transfer coefficient to be 6.5
W/m2/K and that the surrounding wall of the room is at a temperature of 20 oC.
Select one:
A 123.7 W
B. 86.4 W
C. 151.7 W
D. 100.5 W
E 43.0 W
Chapter 1 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 1 - 1.1 On a cold winter day, the outer surface of a...Ch. 1 - 1.2 The weight of the insulation in a spacecraft...Ch. 1 - 1.3 A furnace wall is to be constructed of brick...Ch. 1 - 1.4 To measure thermal conductivity, two similar...Ch. 1 - To determine the thermal conductivity of a...Ch. 1 - A square silicon chip 7mm7mm in size and 0.5-mm...Ch. 1 - A cooling system is to be designed for a food...Ch. 1 - 1.80 Describe and compare the modes of heat loss...Ch. 1 - Heat is transferred at a rate of 0.1 kW through...Ch. 1 - 1.10 A heat flux meter at the outer (cold) wall of...
Ch. 1 - 1.11 Calculate the heat loss through a glass...Ch. 1 - 1.12 A wall with a thickness is made of a...Ch. 1 - 1.13 If the outer air temperature in Problem is...Ch. 1 - Using Table 1.4 as a guide, prepare a similar...Ch. 1 - 1.15 A thermocouple (0.8-mm-diameter wire) used to...Ch. 1 - Water at a temperature of 77C is to be evaporated...Ch. 1 - The heat transfer rate from hot air by convection...Ch. 1 - The heat transfer coefficient for a gas flowing...Ch. 1 - 1.19 A cryogenic fluid is stored in a...Ch. 1 - A high-speed computer is located in a...Ch. 1 - 1.21 In an experimental set up in a laboratory, a...Ch. 1 - 1.22 In order to prevent frostbite to skiers on...Ch. 1 - Using the information in Problem 1.22, estimate...Ch. 1 - Two large parallel plates with surface conditions...Ch. 1 - 1.25 A spherical vessel, 0.3 m in diameter, is...Ch. 1 - 1.26 Repeat Problem 1.25 but assume that the...Ch. 1 - Determine the rate of radiant heat emission in...Ch. 1 - 1.28 The sun has a radius of and approximates a...Ch. 1 - 1.29 A spherical interplanetary probe with a 30-cm...Ch. 1 - A spherical communications satellite, 2 m in...Ch. 1 - A long wire 0.7 mm in diameter with an emissivity...Ch. 1 - Wearing layers of clothing in cold weather is...Ch. 1 - A section of a composite wall with the dimensions...Ch. 1 - A section of a composite wall with the dimensions...Ch. 1 - Repeat Problem 1.35 but assume that instead of...Ch. 1 - 1.37 Mild steel nails were driven through a solid...Ch. 1 - Prob. 1.38PCh. 1 - 1.39 On a cold winter day, the outside wall of a...Ch. 1 - As a designer working for a major electric...Ch. 1 - 1.41 A heat exchanger wall consists of a copper...Ch. 1 - 1.43 A simple solar heater consists of a flat...Ch. 1 - A composite refrigerator wall is composed of 5 cm...Ch. 1 - An electronic device that internally generates 600...Ch. 1 - 1.47 A flat roof is modeled as a flat plate...Ch. 1 - A horizontal, 3-mm-thick flat-copper plate, 1-m...Ch. 1 - 1.49 A small oven with a surface area of is...Ch. 1 - A steam pipe 200 mm in diameter passes through a...Ch. 1 - 1.51 The inner wall of a rocket motor combustion...Ch. 1 - 1.52 A flat roof of a house absorbs a solar...Ch. 1 - Determine the power requirement of a soldering...Ch. 1 - 1.54 The soldering iron tip in Problem 1.53...Ch. 1 - Prob. 1.55PCh. 1 - A pipe carrying superheated steam in a basement at...Ch. 1 - Draw the thermal circuit for heat transfer through...Ch. 1 - 1.60 Two electric resistance heaters with a 20 cm...Ch. 1 - 1.63 Liquid oxygen (LOX) for the space shuttle is...Ch. 1 - The interior wall of a large, commercial walk-in...Ch. 1 - 1.67 In beauty salons and in homes, a ubiquitous...Ch. 1 - The heat transfer coefficient between a surface...Ch. 1 - The thermal conductivity of fibreglass insulation...Ch. 1 - 1.71 The thermal conductivity of silver at 212°F...Ch. 1 - 1.72 An ice chest (see sketch) is to constructed...Ch. 1 - Estimate the R-values for a 5-cm-thick fiberglass...Ch. 1 - A manufacturer in the United States wants to sell...Ch. 1 - Referring to Problem 1.74, how many kilograms of...Ch. 1 - 1.76 Explain a fundamental characteristic that...Ch. 1 - 1.77 Explain each in your own words. (a) What is...Ch. 1 - What are the important modes of heat transfer for...Ch. 1 - 1.79 Consider the cooling of (a) a personal...Ch. 1 - Describe and compare the modes of heat loss...Ch. 1 - A person wearing a heavy parka is standing in a...Ch. 1 - Discuss the modes of heat transfer that determine...
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- An uninsulated 100-mm diameter steam pipe runs for 25-meters inside a room whose walls and air are at a temperature of 25°C. The superheated steam inside the pipe maintains the temperature at the pipe surface at 150°C. If the natural convection heat transfer coefficient of the air outside the pipe is 10- m2-K and the surface emissivity is 0.8, compute for the total rate of heat transfer from the surface of the pipe in kW.arrow_forwardAn electric resistance space heater is designed such that it resembles a rectangular box 50 cm high, 80 cm long, and 15 cm wide filled with 45 kg of oil. The heater is to be placed against a wall, and thus heat transfer from its back surface is negligible. The surface temperature of the heater is not to exceed 75°C in a room at 25°C for safety considerations. Disregarding heat transfer from the bottom and top surfaces of the heater in anticipation that the top surface will be used as a shelf, determine the power rating of the heater in W. Take the emissivity of the outer surface of the heater to be 0.8 and the average temperature of the ceiling and wall surfaces to be the same as the room air temperature. Also, determine how long it will take for the heater to reach steady operation when it is first turned on (i.e., for the oil temperature to rise from 25°C to 75°C). State your assumptions in the calculations.arrow_forwardA 5.1-m internal diameter spherical tank made of 1.6-cm-thick stainless steel (k = 15 w/m- c) is used to store iced water at 0 C. the wall of the room are also at 31 C. The convection heat transfer coefficient at the inner and the outer surface of the tank are 80 w/m - c, respectively. Determine (a) the rate of heat transfer of the iced water and (b) the amount of iced at 0 C that melts during a 24 h period. the heat of fusion of water at atmospheric pressure is 333.7 kj/kg.arrow_forward
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