What is exergy analysis?
What is exergy analysis?
Exergy analysis is a practical approach to evaluate the merit of energy conversion or distribution processes and systems. Exergy analysis involves the application of exergy concepts, balances, and efficiencies to evaluate and improve energy and other systems.
What is exergy formula?
4 Exergy Balance Equation. The exergy destruction and entropy generation are related by the following expression: E x d = T 0 Δ S g e n , where T0 is the reference temperature. If E x d > 0 , then the process is irreversible; if E x d = 0 , then the process is reversible; if E x d < 0 , the process is impossible.
Why is exergy analysis important?
Exergy analysis is an important tool in controlling energy loss during thermal desalination. It helps determine major contributors to exergy destruction and their readjustment in the process to improve overall thermodynamic 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 an example of exergy?
During this time it was usually called availability or available work. As a simple example of exergy, air at atmospheric conditions of temperature, pressure, and composition contains energy but no exergy when it is chosen as the thermodynamic reference state known as ambient.
Can exergy be generated?
Exergy describes the maximum work which can be produced from a system under a given environment. This concept is commonly used in process engineering to estimate (or design) various energy systems such as co-generation systems. Exergy is one of the most widely used goal functions in the structural dynamic modeling.
How is exergy measured?
Exergy is useful when measuring the efficiency of an energy conversion process. The exergetic, or 2nd Law, efficiency is a ratio of the exergy output divided by the exergy input.
Who first developed exergy?
The concept behind exergy is based on “quality of energy.” Sadi Carnot was the first who showed that the produced work from a certain amount of thermal energy divided by that amount of thermal energy is less that one, which means that even under ideal conditions the efficiency of this conversion is less than 100%.
Can exergy be created or destroyed?
Energy is neither created nor destroyed during a process. 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).
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.
How can I improve my exergy?
The exergy efficiency of the overall process can be improved by appropriately utilising this surplus heat. Exergy loss can be minimised either by saving fuel (saving of chemical energy) or by generating steam (saving of thermal energy) to be used in other processes or for power generation.
Can exergy be higher than energy?
In any case the exergy yield = (temperature of coldest available heat reservoir) X (increase in total entropy). So the input exergy is a fraction of input energy. Therefore, the exergy efficiency is higher than the energy efficiency.