On Thermoeconomic Diagnosis of a Fouled Direct Expansion Coil: Effects of Induced Malfunctions on Quantitative Performance of the Diagnostic Technique

Thermoeconomic diagnosis represents a promising technique for the detection of common faults in refrigeration systems, which are responsible of degradation in their energetic performance. Recently, the authors have carried out a sensitivity analysis of the performance of this method to the thermodynamic conditions of inlet air and to the geometry of the direct expansion coil, in case of degradation induced by evaporator fouling. The analysis showed that the method is able to detect this fault, but sometimes its quantitative assessments are not satisfactory. In order to understand more in-depth the origin of such results and identify margins for refinement of the technique, this paper is aimed at evaluating at what extent changes in the exergetic performance of faults-free components may negatively influence the model capability to detect the fouled evaporator and quantify the consequent additional exergy consumption. The results suggest that the method is particularly sensitive to the cost of “induced malfunctions” on the compressor and the condenser, especially when low coil depth or high relative humidity of inlet air are considered.