Question

200-mm-square, 10-mm-thick tile has the thermophysical
properties of Pyrex (   0.80) and emerges from a curing process at an initial temperature of
Ti 140C. The backside of the tile is insulated while
the upper surface is exposed to ambient air and surroundings
at 25C.(a) Estimate the time required for the tile to cool to a final,
safe-to-touch temperature of Tf 40C. Use an average
tile surface temperature of T
–
(Ti Tf)/2 to
estimate the average free convection coefficient and
the linearized radiation coefficient. How sensitive is
your estimate to the assumed value for T
–
?
(b) Estimate the required cooling time if ambient air is
blown in parallel flow over the tile with a velocity
of 10 m/s.

Answer 1