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Homework 10

CM3110

Unsteady-state heat conduction
Radiation

1. For the steel ball in example 5.2-1 in Geankoplis (page 333), calculate the time for the ball's temperature to drop to 600^oF. (SOLUTION)
2. A horizontal heated plate of dimensions 1.0 m by 1.0 m is heated to 50.0^oC. The air over the plate is heated by natural convection and radiation and is at a temperature of 25.0^oC. What is the total heat flux from the plate to the air? The emissivity of the plate, e, is 0.89, and PrGr<10⁷. Which of the two effects (natural convection or radiation) dominates the heat transfer? (SOLUTION)
3. Develop an expression for the net heat transferred between two very wide, very tall plates of cross-section A separated by a radiation shield. The emissivity of the first plate is e₁, of the radiation shield is e₂, and of the second plate is e₃. The answer is
What is the ratio of energy transfer with shield to energy transfer without shield?  Solution:  see instructor
4. What is a black body?  what is a gray body? Solution:  see text
5. Write down an outline of the course, including major and minor topics. In what ways are the momentum-transfer and the heat-transfer parts the same? (SOLUTION)