Second law of thermodynamics, irreversibility

This session deals with the second law of thermodynamics.

It introduces entropy, the uncompensated work, and explains how to calculate most common irreversibilities in energy components.

The two links below provide access to long excerpts of the textbook, to which you should refer.

The first document outlines the basic concepts and various definitions used, and the other is written material on this session.

Course reference:

• “Thermodynamics Fundamentals / Second law”

To follow the presentation, go to next step

• textbook: definitions (pdf 235 Ko)
• textbook: second law (pdf 257 Ko)

(Session realized on 06/15/11 by Renaud Gicquel)

THERMODYNAMICS FUNDAMENTALS

• Second law: irreversibilities
• $ds=\frac{\delta Q}{{\rm T}}+d_{i}s$(2.4.1)
• d_is ≥ 0 entropy generation

THERMODYNAMICS FUNDAMENTALS

• $\delta Q+\delta \pi =Tds$ (2.4.2)
• δQ heat exchanged with the surroundings
• δπ uncompensated heat or work (δπ ≥ 0)

THERMODYNAMICS FUNDAMENTALS

• irreversibilities
• by temperature heterogeneity
• mechanical, due to the viscosity

THERMODYNAMICS FUNDAMENTALS

• irreversibilities by temperature heterogeneity
• temperature difference that must exist in practice for heat transfer
• increase in entropy
$d_{i}s=\left(\frac{T_1-T_2}{T_1{T}_2}\right)\delta Q$ (2.4.8)

THERMODYNAMICS FUNDAMENTALS

• mechanical irreversibilities

• $h_2–h_1={\tau }_s={\int }_1^{2}vdP$
• $h_{\mathrm{2\prime }}–h_2=\pi$
• $h_{\mathrm{2\prime }}–h_1={\tau }_s+\pi$

Second law of thermodynamics, irreversibility

This session has shown the value of concepts such as entropy and the uncompensated work, explaining how to calculate most common irreversibilities in energy components.

The sessions on components show how to evaluate these terms in practice