Aperson puts a few apples into the freezer at -15°c to cool them quickly for guests who are about to arrive. initially, the apples are at a uniform temperature of 20°c, and the heat transfer coefficient on the surfaces is 8 w/m^2c. treating the apples as 9-cm-diameter spheres and taking their properties to be ρ=840 kg/m3, k-0.418 w/m"c, α =1.3 x 10^-7 m^2/s, cp=3.81 kj/kg."c, determine the center temperature of the apples in 1 hour.

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

Adouble-strand no. 60 roller chain is used to transmit power between a 13-tooth driving sprocket rotating at 300 rev/min and a 52-tooth driven sprocket. a) what is the allowable horsepower of this drive? b) estimate the center-to-center distance if the chain length is 82 pitches. c) estimate the torque and bending force on the driving shaft by the chain if the actual horsepower transmitted is 30 percent less than the corrected (allowable) power.

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