The walls of a furnace are made of 1.6-ft-thick concrete (k = 0.64 btu/h⋅ft⋅°f and α = 0.023 ft2/h). initially, the furnace and the surrounding air are in thermal equilibrium at 70°f. the furnace is then fired, and the inner surfaces of the furnace are subjected to hot gases at 1800°f with a very large heat transfer coefficient. determine how long it will take for the temperature of the outer surface of the furnace walls to rise to 70.1°f.

Asingle-geared blanking press has a stroke of 200 mm and a rated capacity of 320 kn. a cam driven ram is assumed to be capable of delivering the full press load at constant force during the last 15 percent of a constant-velocity stroke. the camshaft has an average speed of 90 rev/min and is geared to the flywheel shaft at a 6: 1 ratio. the total work done is to include an allowance of 16 percent for friction a) estimate the maximum energy fluctuation b) find the rim weight for an effective diameter of 1.2 m and a coefficient of speed fluctuation of 0.10

Different types of steels contain different elements that alter the characteristics of the steel. for each of the following elements, explain what the element does when alloyed with steel.

Apipe with an outside diameter of 15 cm is exposed to an ambient air and surrounding temperature of -20°c. the pipe has an outer surface temperature of 65°c and an emissivity of 0.85. if the rate of heat loss from the pipe surface is 0.95 kw per meter of length, the external convective heat transfer coefficient (h) is: (a) 12.5 w/m"k (b) 18.6 w/mk (c) 23.7 w/mk (d) 27.9 w/mk (e) 33.5 w/mk