Heat and Mass Transfer: Fundamentals and Applications
5th Edition
ISBN: 9780073398181
Author: Yunus A. Cengel Dr., Afshin J. Ghajar
Publisher: McGraw-Hill Education
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Chapter 4, Problem 22P
A long copper rod of diameter 2.0 cm is initially at a uniform temperature of 100°C. It is now exposed to an airstream at 20°C with a heat transfer coefficient of’ 200 W/m2 K. How long would it take for the copper rod to cool to an average temperature of 25°C?
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cylinder was thrown into water at 80°C. Calculate how long it will take for the
center temperature of the cylinder to reach 50 °C by taking the convection heat
transfer coefficient as 80W / /m?K.
Thermal properties of the cylinder material
k=0,587 W/m°C
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a = 0,13 x10 * m /s
attachments
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Consider a thin suspended hotplate that measures 0.4 mx 0.4 m. The isothermal plate has a mass of 3.75 kg, a specific heat of 2770
J/kg-K, and a temperature of 200°C. The ambient air temperature is 25°C and the surroundings temperature is 25°C.
If the convection coefficient is 6.4 W/m²-K and the emissivity of the plate is = 0.42, determine the time rate of change of the plate
temperature, dT/dt, when the plate temperature is 200°C. Evaluate the magnitude of the heat losses by convection and by radiation.
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Chapter 4 Solutions
Heat and Mass Transfer: Fundamentals and Applications
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