Exergy analysis of condensation of a binary mixture with one noncondensable component in a shell and tube condenser

The exergy (second-law) efficiency is formulated for a condensation process in a shell and one-path tube exchanger for a fixed control volume. The exergy efficiency η_ex is expressed as a function of the inlet and outlet temperatures and mass flow rates of the streams. This analysis is utilized to assess the trend of local exergy efficiency along the condensation path and evaluate its value for the entire condenser, i.e., overall exergy efficiency. The numerical results for an industrial condenser with a steam-air mixture and cooling water as working fluids, indicate that η_ex is significantly affected by the inlet cooling water and environment temperatures. Further investigation shows that other performance parameters, such as the upstream mixture temperature, air massflow rate, and ratio of cooling water mass flow rate to upstream steam mass flow rate, do not have considerable effects on η_ex. The investigations involve a dimensionless ratio of the temperature difference of the cooling water and environment to the temperature difference of condensation and the environment. Numerical results for various operational conditions enable us to accurately correlate both the local and overall exergy efficiency as linear functions of dimensionless temperature.