Heat and Mass Transfer

Ice cream at a temperature of −18 °C is being transported through a refrigerated truck having outside dimensions of 6 m length, 3 m width and 2 m height. The truck is traveling at a speed of 90 km h⁻¹ on a highway where the air temperature is 45 °C. The truck is insulated in a way such that the outside surface temperature of the truck is maintained at 15 °C. Assume that there is no heat transfer from the front and back of the truck. Properties of air at 30 °C are: ρ = 1.1514 kg m⁻³, μ = 1.86 × 10⁻⁵ Pa s, C_p = 1.007 kJ kg⁻¹ K⁻¹, k = 0.0265 W m⁻¹ K⁻¹. Use the relation: Nu = 0.036 Re^0.8 Pr^0.33. The average heat transfer coefficient of the system is

Options:

• (A) 22.06 W m⁻² K⁻¹
• (B) 30.52 W m⁻² K⁻¹
• (C) 49.56 W m⁻² K⁻¹
• (D) 53.18 W m⁻² K⁻¹