Consider the following statements
1. Availability is generally conserved
2. Availability can either be negative or positive
3. Availability can be destroyed in irreversibilities
Of these statements
Option (A)
3 and 4 are correct
Option (B)
1 and 2 are correct
1 and 3 are correct
2 and 4 are correct
Correct Option:
Question Solution:
The availability or energy is the maximum useful work obtainable from a system as it reaches the dead state. Conversely, availability or energy can regarded as the minimum work required to bring the closed system from the dead state to given state. The value of availability cannot be negative. It a closed system were at any sate other than the dead state. This tendency would stop when the dead state is reached. No work is done to effect such a spontaneous change. Since any change in state can be accomplished with zero work the maximum work cannot be negative. While energy is always conserved but is destroyed by irreversibility