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 1.37P
Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.
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Mild steel nails were driven through a solid
wood wall consisting of two layers, each 15
mm thick, for reinforcement. If the total cross-
sectional area of the nails is 0.75% of the wall
area, determine the unit thermal conductance
of the composite wall, total heat flow, heat
flow through the nail alone and the percent of
the total heat flow that passes through the
nails when the temperature difference across
the wall is 35'C. Neglect contact resistance
between the wood layers. Wood (Pine) (ky) =
0.15 W/(m K); Mild steel (1% C) (kg) = 43 W/(m
K)
а.
ANSWER:
W/m²-K
b.
ANSWER:
A temperature difference of 85•C is impressed across a fiberglass layer of 13 cm thickness. The
thermal conductivity of the fiberglass is 0.035W/m- •C. Compute the heat transferred through
the material per hour per unit area.
4. The section of a vertical wall is made up of fiberglass insulation slabs separated by wooden studs. The thermal conductivity of
fiberglass and wood are 0.04 W/m-K and 0.18 W/m-K, respectively. The thickness of the wall is 160 mm. The temperatures of the
inner and outer surfaces of the wall section are 22 °C and 4 °C, respectively. The ratio of the insulation area to the total wall area is
0.8. Calculate the total heat flow rate (in W/m2) through the wall per unit area.
Wooden Stud
Fiberglass Insulation
Follow-up question to Question 4, calculate the rate of heat flow (in W/m2) through unit area of studs.
Chapter 1 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
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