Thermodynamics Problems

Question

A freezer has an internal temperature of 0°C and is situated in a room with a steady temperature of 20°C. If the freezer is driven by an electric motor 0.5kW in power, calculate the time required to freeze 18kg of water already cooled to 0°C when placed in the freezer. Assume the freezer acts like an ideal heat engine in reverse. 

Answer 1

Internal temperature of the freezer is .

Steady temperature of the room is .

Freezer is driven by an electric motor in power.

Mass of the water placed in the freezer is .

Heat energy gained or lost by a substance is .

where .

.

Energy in terms of power is .

Therefore,

Substitute corresponding values in the expression.

Time required to freeze 18 kg of water already cooled to is 50.232 mins.