Question 1

Sheets of steel are typically made by rolling heated steel at high temperatures, resulting in a

flat plate as shown in figure 1. The resulting hot flat plates are cooled by passing air at a fixed

temperature of 295 K over the plate. The plate is 4 m long, and 1.2 m wide, and has a uniform

temperature of 600 K. The velocity of the flow of air is 9.5 m/s.

Air

4 m

Figure 1: Flow of air over a flat plate.

Assuming the sheets are oriented such that the air flow along the length of the plate (i.e., along

the a direction, as denoted by the blue arrow), calculate:

a) The local heat transfer coefficient at a distance 1 m from the leading edge of the plate

(i.e. at z = 1 m) [4 marks]

b) The average heat transfer coefficient over the entire plate [3 marks]

c) The rate of heat transfer from the plate to the air. [1 mark]

If the plate is re-oriented such that the flow of air now flows along the width of the plate (i.e.

along the y direction, as denoted by the red arrow), calculate the rate of heat transfer from the

plate to the air. [4 marks]

In all cases above, you may neglect any heat transfer from the bottom of the plate.