1. A reversible process has been defined as a process, which having taken place, can be reversed and in so doing leaves no change in either the system or the surroundings. Six restrictions were imposed

a. no friction

b. heat transfer occurs only for infinitesimal temperature differences

c. unrestrained expansion does not occur

d. no mixing

e. no turbulence

f. no combustion

Choose a process for which one of these restrictions is relaxed and discuss how this process is not reversible.

2. Thirty five (35) kilograms of chicken is to be frozen in a household freezer. The chicken is at 15⁰C when it is placed in the freezer and reaches -20⁰C (well below the freezing point) in 3 hours. If the COP of the freezer is 4.3 during this process, determine the required power input (in kW).

Hint: You will need to perform a first law analysis on the chicken to determine the QL for the refrigerator. Some properties of the chicken that will be useful:

Freezing point for the chicken: -2.8°C

cP for unfrozen chicken: 3.32 kJ/(kg?K)

cP for frozen chicken: 1.77 kJ/(kg?K)

energy that must be removed to freeze chicken: 247 kJ/kg

(also called the latent heat of fusion)