Consider the boundary layer on the four walls to be turbulent and the heat transfer only from the four surfaces.

Question

A refrigerated truck carrying foodstuff is speeding on a highway at 90 km/h in a desert area where the ambient air temperature is 55°C. The body of the truck may be modeled as a rectangular box measuring 11 m long, 4 m wide and 3 m high. Consider the boundary layer on the four walls to be turbulent and the heat transfer only from the four surfaces. The wall surfaces of the truck are maintained at 10 °C. Assume the flow to be parallel to 11m long side. The thermo-physical properties at the mean-film temperature of 32.5°C are:

      $\rho$= 1.165 kg/m³, c_p = 1.005 kJ/kg-K,

      k = 2.673 $\times$10^–2 W/m-K,

      V  = 16 $\times$10^–6 m²/s   and   Pr = 0.701

      Work out the following

(i)   Sketch the system and show the boundary layer development along length

(ii) Heat loss from the four surfaces

(iii) Tonnage of refrigeration needed

(iv)    Power required to overcome the resistance acting on four surfaces