A refrigerated truck has a dimension of 12m*2m*3m. The cargo space at the refrigerated truck is to be cooled from 25(oC) to 6(oC). The heat lost by transmission is 1kJ/s and the power input of the refrigeration system is 10kW?

Density of air is 1.2 kg/m3. Specific heat of air is 1.005 kJ/Kg(oC)
Calculate the time it takes to cool the truck.

From these data, i was able to calculate the mass of air ( 86.4 kg ) and the amount of heat removed to cool the truck from 25(oC) to 6(oC) which i obtained as 1649.8 kJ .
How should i proceed to calculate the time?

1 Answer
May 1, 2018

Excuse me if I'm wrong, but you're making this overcomplicated, the answer is in your question!

The transmission loses the heat at a rate of,

# (1"kJ")/"s"#

Hence, it would take approximately,

#1649.8"kJ" * "s"/(1"kJ") approx 27.5"min"#

to cool the truck with that transmission.