Where, h is specific Enthalpy, u is specific internal energy, v is specific volume, p is the pressure.īy differentiating the eq (4) and substituting it in above equation, thenīoth of above equations are related to changes in entropy for reversible processes on account of changes in internal energy and volume in former and to change in enthalpy and pressure in later equation. Where, q rev denotes heat transfer along a reversible path.Įnthalpy (h) is the property of state and is defined as, Entropy is the subject of second Law of thermodynamics which describes entropy change in system and surrounding with respect to Universe.Įntropy is defined as ratio heat transfer to the absolute temperature in a system for a reversible thermodynamic path. The entropy is represented by symbol s and change in entropy Δs in kJ/kg-K. Like internal energy, Entropy and Enthaly are thermodynamic properties. Professions are busy in putting their efforts to bring down the effects of irreversibility in processes and mechanisms. Irreversibility persists on account of variation in pressure, composition, temperature, composition main caused by heat transfer, friction in solid and liquid, chemical-reaction. Entropy of the system increases sharply in irreversible process and the value can’t be brought back to the initial value from the final value. ![]() In irreversibile process the initial state of the system and surrounding can’t be bring back to initial state from final state. When actual processes fails to meet the requirements of reversibility, then the processes is called irreversible. In order to measure the success of a real processes, professionals uses reversible process as the measure for comparing and bringing the real and actual processes closer to reversibility by lowering down losses in order to increase the efficiency of the processes. Reversible-process is one that is reversible both internally and externally. The process is said to be externally-reversible environment accompanying the change can also be reversed-in-sequence. The process is said to be reversible-internally if the original state is re-stored in reverse direction. If temperature (t) and pressure (p) variations are infinitesimal in a system, which is undergoing-a-process, then the process can be termed as near equilibrium states or approaching reversibility. The second law of thermodynamics categories the processes under two heads Properties like pressure, volume, enthalpy, temperature, entropy etc changes during a thermodynamic process. Reversibility and IrreversibilityĪ system is said to be undergoing a process when it initial state changes to final state. In a rigid and isolated adiabatic system (w = 0, q = 0), then its internal energy(u) remains unchanged. In this equation q and w are the net heat transferred and net work for the process respectively, while uf and ui are final and initial values of internal energy(u). It is the outcome of the First law of thermodynamics and is related to equation (1) if a system involves an arbitrary process. Engineering thermodynamics further explores the concepts of systems and processes. Substituting above in equation (1) then,Įquation (2) is the representation of integral of all work done by the system or net work done by the system is equal to the integral of all heat transfer into the system. ![]() Initial and final state of internal energy in the above equation is represented by i and f. Final state is same as the original state and there is no change in internal energy of the system.Integration of any state property differential is the difference of its limits.
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