Entropy losses in chemical processes

How entropy can be reduced

Let us start with how one reduces the entropy of his process

You can always reduce the entropy of a system by removing energy from it by heat transfer.

ds >= δ/QT?

ds =?δQ/T?+ I

I is the entropy generated due to irreversibilities.

If heat?δQ leaves a system, it will be negative by convention.

ds = - δ/QT?+ I

If you remove heat?δQ from a body at temperature T, such that?δQT?is greater than I , then ds will be negative. You have reduced the entropy of the system.

In doing so, however, the entropy of the surroundings will increase by a greater amount, ensuring the entropy of the universe will always increase.

Entropy is non-conserved.

How entropy is generated?

Entropy is produced in irreversible processes. Processes like, heat and mass transfer activities, fluid flow, substances expanding or mixing, and any irreversible thermodynamic cycle, such as thermal machines like power plants, heat engines, refrigerators, heat pumps, and air conditioners, all produce entropy.

What exactly does that imply?

Entropy is a measure of the work value of the energy in a system; maximum entropy (thermodynamic equilibrium) indicates that the energy has no work value, whereas low entropy indicates that the energy has a high work value. The universe’s energy is constant, but its utility decreases as the entropy of the world rises.

What is entropy?

Entropy is a disorder.

The definition of entropy S, dS = Qrev / T, is connected with the mathematical expression of the second law. Entropy is a non-conserved thermodynamic potential that provides a quantitative measure of irreversibility. For reversible processes, dS is an accurate differential of the state function entropy, and the integration's ultimate result is independent of the process's route or how it is manifested, as long as the beginning and final states are stable equilibrium states.

Closed adiabatic system

In a reversible process, the entropy of a closed adiabatic system remains constant, while it increases in an irreversible process. The sum of the entropies of all bodies involved in a reversible change remains constant during reversible processes and increases during irreversible processes, creating an isolated system. Entropy can be used to determine whether a process is reversible or irreversible. Both entropy and time are intricately linked to the behavior of natural events, and the fundamental law for closed, adiabatic systems, dS/dt > 0, can be thought of as the arrow of time's pointer.

Entropy balance

An entropy effect exists in every non-equilibrium system, either within the system or through the system's boundary. Entropy is a broad attribute, and if a system is made up of numerous components, the total entropy equals the sum of each part's entropies. For every system undergoing an irreversible process, the entropy balance can be represented as

Change in total entropy = [Entropy in – Entropy out] = Entropy generated

?The entropy generation value cannot be negative, however, the changes in the system's entropy can be positive, negative, or zero. The increase of entropy principle states that the entropy of an isolated system grows throughout an irreversible process. Without knowing the details of the operation, entropy change can be calculated. The entropy generation of a reversible process is zero, and the entropy change of a system is equal to the net entropy transfer. The entropy balance is similar to the energy balance.

?The following are some examples of entropy concepts:

-Entropy production is a measure of dissipated useful energy and degradation of the performance of engineering systems, such as transportation and rate processes; the amount of dissipation is determined by the number of irreversibilities present during the operation.

-Entropy is a nonconserved property that can only be conserved in an ideal reversible process.

- A reversible adiabatic process is isentropic, meaning the entropy values at the input and outlet are the same. Pumps, turbines, nozzles, and diffusers are adiabatic activities, and their performance will be good when the process's irreversibilities, such as friction, are decreased, and they are thus operated under isentropic conditions.

- A turbine's isentropic efficiency T at steady state is defined as the ratio of the turbine's actual work output Wa to the work output of isentropic operation, Ws

- Entropy can be transferred by heat and mass flows. The entropy gained or lost by a system during a process is represented by entropy exchange through the system boundary.

- Work does not transfer entropy.

- There is no distinction between heat and work, according to the first law of thermodynamics. However, according to the second law, an energy exchange that includes entropy transfer is heat transfer, and an energy exchange that does not include entropy transfer is work.

Last but not least, how may entropy be reduced?

To establish the links between the physical configuration and entropy generation, thermodynamics, fluid mechanics, heat and mass transfer, kinetics, material qualities, restrictions, and geometry are required. In general, reducing entropy generation is achieved through altering design and operational circumstances.

Credit: Google