Question

To make ice, a freezer that is a reverse Carnot engine extracts 37 kJ as heat at -17°C during each cycle, with coefficient of performance 5.8. The room temperature is 26.9°C. How much (a) energy per cycle is delivered as heat to the room and (b) work per cycle is required to run the freezer?

Answer 1

Answer:

a) 6.4 kJ

b) 43.4 kJ

Explanation:

a)

$Q_{a}$ = Heat absorbed = 37 kJ

$β$  = Coefficient of performance = 5.8

$W$ = Work done

Heat absorbed is given as

$Q_{a}$ = $β$ $W$

37 = (5.8) $W$

$W$ = 6.4 kJ

b)

$Q$  = work per cycle required

$Q$  = $Q_{a}$ + $W$

$Q$  = 37 + 6.4

$Q$  = 43.4 kJ