External exergy loss

Examples of such external exergy losses are the release of hot flue gases or high-pressure gas to the atmosphere. Both the internal and the external exergy losses are in principle inefficiencies, and the exergy used efficiently in the process is therefore only the exergy of products and the exergy of waste products, provided they are made useful in other processes. 

Erejea = H2 - H10 - T0 S2 -, S 2 0). We may call Erejea the external exergy loss in contrast to which is called the internal exergy loss. 

In the natural environment, however, there are components of states differing in their composition or thermal parameters from thermodynamic equilibrium state. These components can undergo thermal and chemical processes. Therefore, they are natural resources with positive exergy. Only for commonly appearing components can a zero value of exergy be accepted. A correct definition of the reference level is essential for the calculation of external exergy losses. The most probable chemical interaction between the waste products and the environment occurs with the common components of the environment. 

Local gross exergy loss 8used technology for the major product and byproduct, and it can be calculated from the following steady-state exergy balance ... 

Exergy is an extensive property and a thermodynamic potential. In contrast to energy, exergy is not conserved and decreases in irreversible processes. If we discharge the waste product of the process into the environment, external exergy loss occurs due to the deviation of thermal parameters and the chemical composition between the product and the components of the environment. The thermal state and chemical composition of the natural environment represent a reference level (dead state) for the calculation of exergy. 

Figure 15.3 Exergy analysis results for the process units in the FP-FC system, (a) Internal and external exergy losses (b) rational efficiencies.

Only part of the enthalpy from reaction (3) is available as external work (ex-ergy or Gibbs free energy). The rest is dissipated in the fuel cell as heat and mainly removed with the cathode air through heat exchanger E3. This heat transfer is the main source of exergy losses in the plant. 

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