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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Exercise 1: Radiation Effect on Thermal Comfort
It is a common experience to feel "chilly" in winter
and "warm" in summer in our homes even when the
thermostat setting is kept the same. This is due to
the so called "radiation effect" resulting from
radiation heat exchange between our bodies and the
surrounding surfaces of the walls and the ceiling.
Consider a person standing in a room maintained at
22°C at all times. The inner surfaces of the walls,
floors, and the ceiling of the house are observed to
be at an average temperature of 10°C in winter and
25°C in summer.
Determine the rate of radiation heat transfer between
this person and the surrounding surfaces if the
exposed surface area and the average outer surface
temperature of the person are 1.4 m2 and 30°C,
respectively.
Exercise 2: Heat Loss from a Person
Consider a person standing in a breezy room at
20°C. Determine the total rate of heat transfer from
this person if the exposed surface area and the
average outer surface…
1.4)
True/False: The heat flux in a circular tube with laminar forced convection
will be higher near the inlet of the tube and gradually decreases to the fully
developed value.
1.5) Fill in the blanks: A body whose surface properties are independent of
The emissivity of a
is
wavelength is said to be a
one for all wavelengths, the emissivity of a
is between zero and
one.
1.6) Fill in the blanks: The thermal resistance of the tube in a heat exchanger is
and the
usually negligible when the wall thickness of the tube is
thermal conductivity of the tube material is
1.7) True/False: The heat transfer in a heat exchanger will reach its maximum
value when the cold fluid is heated to the inlet temperature of the hot fluid.
Therefore, the temperature of the cold fluid cannot rise above the inlet
temperature of the hot fluid at any location in a heat exchanger.
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