Enthalpy exergy analysis

As some intermediate thermodynamic data are missing or not well known (enthalpy of mixing of CuCl and CuCl2 in HC1/H20 mixtures for example) and some heat exchanges or separation are not linear (for instance, HC1/H20 mixture has an azeotrope which cannot be crossed), we decided to proceed to a global exergy analysis instead of a flow sheet analysis. 

Table 2.10 Enthalpy and exergy analysis of an ammonia plant. I. Dybkjaer [169].

The second contribution Ex is the transfer of the compounds in the mixture from 1 atm partial pressure at 25 °C to the actual temperature and the actual partial pressures in the mixture. This is done by use of Eq. (13), where the enthalpy and entropy differences are calculated by standard methods. An example of results obtained by exergy analysis of an ammonia production process is given in Sect. 6.5.3.1.2. 

The analysis requires the calculation of three exergy flow rates, at 0°C, 50°C, and 100°C. As no heat or work is transferred between the considered system and its environment, the first law, Equation 6.1, yields that the overall enthalpy change is zero ... 

The objective of this work is to develop a set of group contributions for estimating the specific chemical enthalpy, 8, and the specific chemical exergy, e, which are essential in carrying out the thermodynamic analysis and synthesis of a process system. This set of group contributions can be employed not only for known organic compounds, but also for new organic compounds which are yet to be synthesized or discovered. 

Of the variables listed for process design, mass and energy (usually in the form of heat, enthalpy, and exergy) are of most interest. These variables may also be used for planning, evaluation of systems, analysis, and synthesis. 

An entropy effect leading to energy dissipation or exergy loss either within or through the boundary of a system is unavoidable in every irreversible system. Thermodynamic analysis determines the net enthalpy deficits and exergy losses due to irreversibility at each stage of a distillation column by combining the first and second laws of... 

---