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  1. A steel billet of 2000 kg mass is to be cooled from 1250 K to 450 K. The heat released during this process is to be used as a source of energy. The ambient temperature is 303 K and specific heat of steel is 0.5 kJ/kgK. The available energy of this billet is
    1. 490.44 MJ
    2. 30.95 MJ
    3. 10.35 MJ
    4. 0.10 MJ
Correct Option: A

Heat lost by steel = (0.5)(2000)(450 – 1250) Gained = 800MJ

∆SLost by steel = (2000) (0.5)) ln
450
1250

⇒ –1.021 MJ
(∆S) gained = 1.021MJ
AE (W) = a – T0 dS
= 800 – (303) (1.021)
= 490.7 MJ



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