A large truck is to transport 30,000 Kg of orange pre-cooled to 4oC

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SUMMARY

The discussion focuses on calculating the refrigeration load for transporting 30,000 Kg of oranges pre-cooled to 4°C in a truck under an ambient temperature of 27°C. The heat transfer rate is defined as UA=80W per °C temperature difference, with an air inflow rate of 4L/s and an average heat of respiration of 0.017W/kg. The analysis requires applying the 1st Law of Thermodynamics and determining the mass flow rate of air using its density of 1.15kg/m³. The goal is to compute the total refrigeration load and the amount of ice necessary for a 15-hour trip.

PREREQUISITES
  • 1st Law of Thermodynamics
  • Heat transfer principles
  • Mass flow rate calculations
  • Thermodynamic properties of air and respiration heat
NEXT STEPS
  • Calculate mass flow rate of air using volumetric flow rate and density
  • Determine total heat transfer using UA value and temperature difference
  • Compute total refrigeration load over a 15-hour period
  • Calculate the amount of ice required to meet refrigeration needs
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Transport engineers, logistics managers, and anyone involved in the refrigeration of perishable goods during transport will benefit from this discussion.

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A large truck is to transport 30,000 Kg of orange pre-cooled to 4oC under average temperature of 27oC. The structure of the walls of the truck is such that the rate of heat transportation is UA=80W per oC temperature difference between the ambient and the oranges. From past experience, ambient air is estimated to enter the cargo space of the truck through the cracks at a rate of 4L/s. Also, the average heat of respiration of the oranges at 4oC is 0.017W/kg for this particular load. Disregarding any condensation and taking the density of air to be 1.15kg/m3, determine the refrigeration load of this truck and the amount of ice needed to meet the entire refrigeration need of the truck for a 15hour trip.

Can you help me on figuring out how to start this question?
 
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The 1st Law of Thermodynamics is always a good place to start. Use the volumetric flow rate of the air and its density to figure out the mass flow rate, then look up the necessary properties from the appropriate table. Keep in mind conservation of mass though, if this is a steady state problem then equal amounts of mass will enter and leave the system.