Two options are being considered to cool a can of a soft drink from an initial temperature of 35°C to a maximum temperature of 15°C as quickly as possible. The can is 5 cm in diameter and 20 cm long. Option A:

place the can in a refrigerator where air at 4°C is blown over the can perpendicular to its axis of at a velocity of 0.1 m/s. Option B: place the can under a stream water at 10°C flowing perpendicular to its axis at a velocity of 0.5 m/s and covering the entire surface of the can. The soft drink inside the can is assumed to be stagnant in both cases and may be treated as a solid with the physical properties listed below. For both options A and B: (a)

Estimate as accurately as possible the convective heat transfer coefficient.

(b) Calculate the Biot number and state which resistance is dominant. (c)

Estimate the time required to achieve an average temperature of 15°C. (d)

Estimate the surface temperature of the can when its average temperature reaches 15°C. Properties of the soft drink: thermal conductivity = 0.5 W/m K, density = 950 kg/m³, heat capacity = 3,900 J/kg K.