Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 12, Problem 12.81P
A radiation thermometer is a radiometer calibrated to indicate the temperature of a blackbody. A steel billet having a diffuse, gray surface of emissivity 0.8 is heated in a furnace whose walls are at 1500 K. Estimate the temperature of the billet when the radiation thermometer viewing the billet through a small hole in the furnace indicates 1160 K.
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Students have asked these similar questions
A space satellite in the shape of a sphere is traveling in outer space, where its surface temperature is held at 315.2K. The sphere “sees” only outer space, which can be considered as a black body with a temperature of 2K. The polished surface of the sphere has an emissivity of 0.15. Calculate the heat loss per m2 by radiation.
An opaque, diffuse, gray, square (200 mm x 200 mm) plate with an emissivity of 0.8 is placed over the opening of a furnace (L = 200
mm) and the plate temperature is known to be 400 K at a certain instant. The bottom of the furnace, having the same dimensions as
the plate, is black and operates at 1040 K. The sidewalls of the furnace are well insulated. The top of the plate is exposed to ambient air
with a convection coefficient of 25 W/m².K and to large surroundings. The air and surroundings are each at 300 K.
Air
9₁ =
To
h
=
W
-Plate
(a) Evaluate the net radiative heat transfer to the bottom surface of the plate, in W.
T SUT
-Insulated sidewalls
-Furnace bottom
O
(b) If the plate has mass and specific heat of 2 kg and 900 J/kg-K, respectively, what will be the change in temperature of the plate with
time, dTp/dt, in K/s? Assume convection to the bottom surface of the plate to be negligible.
dT₁ =
K/s
dt
Two large parallel surfaces (surface 1 and surface 2) kept at constant surface temperature of T1= 300 °C
and T2= 100 °C. The two surfaces have emissivity of ɛ1= 0.8 and ɛ2= 0.5 respectively. The top surface
(surface 2) is cooled by convective heat transfer with surrounding air temperature of 20 °C. The bottom
surface (surface 1) is well insulated at the backside. Assume the surfaces are diffuse and gray, and the
space between the surfaces is vacuum.
a. Calculate the radiation heat transfer between the surfaces per unit area [W/m?].
b. Calculate the convective heat transfer coefficient for the top surface [W/m2 K].
Chapter 12 Solutions
Fundamentals of Heat and Mass Transfer
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