A 200-mm-square, 10-mm-thick tile has the thermo physical properties of pyrex ( = 0.80) and emerges from

A 200-mm-square, 10-mm-thick tile has the thermo physical properties of pyrex (ε = 0.80) and emerges from a curing process at an initial temperature of T_i = 140°C. The backside of the tile is insulated while the upper surface is exposed to ambient air and surroundings at 25°C.

(a) Estimate the time required for the tile to cool to a final, safe-to-touch temperature of T_f = 40°C. Use an average tile surface temperature of T = (Ti + T_f)/2 to estimate the average free convection coefficient and the linearized radiation coefficient. How sensitive is your estimate to the assumed value for 1'?

(b) Estimate the required cooling time if ambient air is blown in parallel flow over the tile with a velocity of 10 m/s.

Transcribed Image Text:

Ts = 25°C Ambient air T- 25°C -Tile, T,