Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 3, Problem 3.58P
An electrical current of 700 A flows through a stainless steel cable having a diameter of 5 mm and an electrical resistance of
- If the cable is bare. what is its surface temperature?
- If a very thin coating of electrical insulation is applied to the cable. with a contact resistance of
- There is some concern about the ability of the insulation to withstand elevated temperatures. What thick-ness of this insulation
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Question 1: A glass window of width W = 1 m and height H = 2 m is 5 mm thick and has a thermal conductivity of kg =1.4 W/m.K. If the inner and outer surface temperatures of the glass are 15 oC and -20 oC, respectively, on a cold winter day, what is the rate of heat loss through the glass? To reduce heat loss through windows, it is customary to use a double pane construction in which adjoining panes are separated by an air space. If the spacing is 10 mm and the glass surfaces in contact with the air have temperatures of 20 oC and -15 oC, what is the rate of heat loss from a 1 m x 2 m window? The thermal conductivity of air is ka = 0.024 W/m.K.
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Question 4
The window of a room is made of 5 mm thick glass which has a thermal conductivity of 1.4 W/m-K.
A heater is used to maintain the room temperature at 22 °C. Take the convection heat transfer
coefficients on the outer surface of the window to be 12 W/m²-K.
Take appropriate assumptions while solving this problem.
(a)
T₁=15°C
TA
-A- 1m x 3m = 3m²,
k=1.4W/m-K
-T₂=5°C
L=0.005m
Figure Q2
Determine the heater thermal load to maintain the room temperature?
Chapter 3 Solutions
Fundamentals of Heat and Mass Transfer
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