In many studies, exergy destruction and exergy loss occurred simultaneously. When describing them, it is usually explained that they are caused by irreversibility, such as temperature difference, friction or adiabatic throttling. What is the essential difference between exergy damage and exergy loss?
Hello Rong Zhao,
Every time you convert energy from one form to another, there are losses. For example, an electric motor converts electrical power into rotational motion. Heat and sound are two forms of unintended energy conversion that would be labeled as parasitic energy loss. The less the parasitic loss, the higher the efficiency.
That said, the law of conservation of energy states that energy cannot be created nor destroyed.
I think this is a case of language where a synonym was improperly chosen (hence why they "occurred simultaneously"). To say energy is destroyed or damaged is incorrect. Energy is converted. That conversion can be then sorted into subcategories such as: The intended conversion (rotational motion in the example above) or parasitic loss (heat and sound in the example above).
Best regards,
Eric S.
Hello Rong Zhao,
The choice of boundary can determine whether the effects of heat transfer should be charged as an exergy destruction or an exergy loss.
I suggest you read section 3.5.2 of Bejan's book titled "Thermal design and optimization". This section titled "Exergy Destruction and Exergy Loss" has interesting content that answers your question.
Regards,
Zahra HMT.
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