Question

For irreversible process, which relation is correct?
1. loss of exergy is indirectly proportional to rate of entropy generation
2. loss of exergy is directly proportional to rate of entropy generation
3. loss of exergy has no relation with rate of entropy generation
4. loss of exergy is equals to rate of entropy generation

Answer 1

Correct Answer - Option 2 : loss of exergy is directly proportional to rate of entropy generation

Explanation:

Exergy (or) Available Energy:

The maximum portion of energy that could be converted into useful work by ideal processes that reduce the system to a dead state(a state in equilibrium with the earth and its atmosphere).
W_max = I + W_act 

where I = Irreversibility (loss of available energy)

According to the Gouy-Stodola theorem, the loss of available energy (Irreversibility) is given by To(ΔS)gen

where To is the atmospheric temperature and (ΔS)gen is the entropy generation due to the heat transfer from one reservoir to another reservoir.

Wmax =  To(ΔS)gen + Wact 

∴ Loss of exergy is directly proportional to the rate of entropy generation.