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 2, Problem 2.30P
An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of
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Question No. 11: a) Derive the general heat conduction equation in Cartesian coordinates.
b) Electric heater wires are installed in a solid wall having a thickness of 8 cm and k =2.5W/m ◦C.The right face is exposed to an environment with h=50W/m2◦C and T∞ = 30°C, while the left face is exposed to h=75W/m2◦C and T∞ =50◦C. What is the maximum allowable heat-generation rate such that the maximum temperature in the solid does not exceed 300◦C?
1. For a steam pipe with a given diameter of 10 cm covered by two (2) layers of
insulation. The first insulation has a thickness of 4 cm and a coefficient of thermal
conductivity of 0.08 W/m.K. and the second insulation has a thickness of 3 cm and
a thermal conductivity of 0.15 W/m.K. The steam main conveys steam at a
pressure of 1.70 MPa with 25°C superheat. Outside temperature is 27°C. The pipe
is 30 meters in length. (tsat @ 1.70 MPa = 204°C). Determine the following:
a) The heat loss in KW
b) Explain the concepts/principles that were considered and the factors that
affected the condition of the above mentioned items (a & b).
An electric cable consists of an inner core and an outer protection layer. The shape of the cable can be approximated as a cylinder. The diameter of the inner core is D1 = 1.6 cm and the total diameter of the cable is D2 = 2 cm. The thermal conductivities for the cable inner core and outer layer are k = 50 W/m·K and k = 0.1 W/m·K, respectively. The electric current in the inner core causes a volumetric thermal energy generation rate of q ̇ = 10^(6) W/(m^(3)) . The cable is placed in an air crossflow of u∞ = 2 m/s and T∞ = 300 K. The air in the film around the cylinder has a kinematiccrossflow of u∞ = 2 m/s and T∞ = 300 K. The air in the film around the cylinder has a kinematic viscosity of ν = 2 × 10^(−5 )(m^2)/s, thermal conductivity of kf = 0.025 W/m · K, and Prandtl number of Pr=0.7.
Assume one-dimensional and steady-state conduction heat transfer along the radial direction of the cable cross section. Perform heat transfer analysis for a section of the cable with length L = 10 cm.…
Chapter 2 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 2 - A plane wall, 7.5 cm thick, generates heat...Ch. 2 -
2.2 A small dam, which is idealized by a large...Ch. 2 - 2.3 The shield of a nuclear reactor is idealized...Ch. 2 - A plane wall 15 cm thick has a thermal...Ch. 2 - 2.5 Derive an expression for the temperature...Ch. 2 - A plane wall of thickness 2L has internal heat...Ch. 2 - 2.7 A very thin silicon chip is bonded to a 6-mm...Ch. 2 - 2.9 In a large chemical factory, hot gases at 2273...Ch. 2 - 2.14 Calculate the rate of heat loss per foot and...Ch. 2 - 2.15 Suppose that a pipe carrying a hot fluid with...
Ch. 2 - Prob. 2.16PCh. 2 - Estimate the rate of heat loss per unit length...Ch. 2 - The rate of heat flow per unit length q/L through...Ch. 2 - A 2.5-cm-OD, 2-cm-ID copper pipe carries liquid...Ch. 2 - A cylindrical liquid oxygen (LOX) tank has a...Ch. 2 - Show that the rate of heat conduction per unit...Ch. 2 - Derive an expression for the temperature...Ch. 2 - Heat is generated uniformly in the fuel rod of a...Ch. 2 - 2.29 In a cylindrical fuel rod of a nuclear...Ch. 2 - 2.30 An electrical heater capable of generating...Ch. 2 - A hollow sphere with inner and outer radii of R1...Ch. 2 - 2.34 Show that the temperature distribution in a...Ch. 2 -
2.38 The addition of aluminum fins has been...Ch. 2 - The tip of a soldering iron consists of a 0.6-cm-...Ch. 2 - One end of a 0.3-m-long steel rod is connected to...Ch. 2 - Both ends of a 0.6-cm copper U-shaped rod are...Ch. 2 - 2.42 A circumferential fin of rectangular cross...Ch. 2 - 2.43 A turbine blade 6.3 cm long, with...Ch. 2 - 2.44 To determine the thermal conductivity of a...Ch. 2 - 2.45 Heat is transferred from water to air through...Ch. 2 - 2.46 The wall of a liquid-to-gas heat exchanger...Ch. 2 - Prob. 2.47PCh. 2 - The handle of a ladle used for pouring molten lead...Ch. 2 - 2.50 Compare the rate of heat flow from the bottom...Ch. 2 - 2.51 Determine by means of a flux plot the...Ch. 2 - Prob. 2.52PCh. 2 - Determine the rate of heat transfer per meter...Ch. 2 - Prob. 2.54PCh. 2 - 2.55 A long, 1-cm-diameter electric copper cable...Ch. 2 - Prob. 2.56PCh. 2 - Prob. 2.57PCh. 2 - Prob. 2.58P
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