Pietro Catrini

Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coils

Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and thermal fractions of air exergy. The examined parameters are the temperature and humidity of inlet air, the humidity of reference state and the sensible/latent heat ratio (varied by considering different coil depths). The exergy analysis reveals that due to the more intense dehumidification occurring in presence of fouling, the exergy efficiency of the evaporator coil eventually increases. Once the diagnostic technique is based only on the thermal fraction of air exergy, the results suggest that the performance of the technique increases when inlet air has a lower absolute humidity, as evident from the “optimal performance” regions identified on a psychrometric chart.

Thermodynamic, Exergy, and Thermoeconomic analysis of Multiple Effect Distillation Processes

Abstract Multiple effect distillation (MED) is nowadays the preferred technology for the construction of new plants based on thermal processes in the growing desalination market. MED technology, in fact, presents a number of advantages with respect to the more traditional multistage flash technology, among all the lower energy consumption achievable in MED plants. However, a large potential for improvement in terms of lowering production costs still exists, which stimulates further efforts on process optimization from companies and researchers involved in the field. Thermodynamic and exergy analysis provides useful insights regarding the identification of main inefficiencies and the margins for performance improvements. A number of works have focused their attention on these aspects, presenting innovative investigation tools eventually applied to theoretical or real case studies. In the present chapter, the fundamentals of thermodynamic and exergy analysis for MED process optimization are presented. “Exergy costing” is also discussed and proposed as an innovative method capable of reflecting how thermal inefficiencies contribute to a gradual increase in the economic value (to be intended as a cost of generation) of material streams along the process. In order to achieve a more comprehensive view, the aforementioned analyses are carried out for a reference MED plant assumed as the case study.