Is exergy efficiency higher than energy efficiency?
So the input exergy is a fraction of input energy. Therefore, the exergy efficiency is higher than the energy efficiency.
How do you calculate exergy efficiency?
(EEF) of Complex Systems 1988) that the exergy efficiency of the system on the whole can be calculated as the ratio of total useful exergy effect of the system (product) to available exergy (fuel).
What is the difference between energy and exergy?
Energy of a particular substance is the ability of that substance to do work while exergy is a thermodynamic term which describes the maximum useful work that a substance can perform during the process of bringing a system into equilibrium with a heat reservoir. This is the key difference between energy and exergy.
What is 2nd Law efficiency?
Second Law Efficiency Second Law efficiency is a measure of how much of the theoretical maximum (Carnot) you achieve, or in other words, a comparison of the system’s thermal efficiency to the maximum possible efficiency. The Second Law efficiency will always be between the Carnot and First Law efficiencies.
How do you calculate Exergy efficiency of a refrigerator?
where ̇ExQ,evap is the thermal exergy rate of the evaporator due to the heat transfer ˙QL from refrigerated space and is calculated as ̇ExQ,evap=˙QL(T0/TL−1) .
What is the difference between exergy and entropy?
The entropy of a system is only related to the state of the system and is unrelated to the environment; in contrast, the exergy of a system is not only related to the state of the system but also related to the state of the environment, making it too complicated.
What is the purpose of exergy?
Exergy-based analyses are very convenient methods for assessing the performance of energy conversion systems. Exergy is the maximum work that can be obtained from a system. Exergy-based analyses help determine the irreversibilities (entropy generation) and how a source can be used effectively.
Can exergy be created or destroyed?
Exergy is the energy that is available to be used. After the system and surroundings reach equilibrium, the exergy is zero. Energy is neither created nor destroyed during a process. Energy changes from one form to another (see First Law of Thermodynamics).
What is the difference between 1st and 2nd Law efficiency?
The basic difference between both concepts is that while first law efficiency solely relates to the specific technology applied in order to satisfy certain tasks, for example, illumination and space heating, the concept of second law efficiency takes into account both the actual technology employed and the technology …
Can exergy be destroyed?
Energy changes from one form to another (see First Law of Thermodynamics). In contrast, exergy is always destroyed when a process is irreversible, for example loss of heat to the environment (see Second Law of Thermodynamics). The destroyed exergy has been called anergy.