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

Journal of Sustainable Development of Energy, Water and Environment Systems
Volume 5, Issue 2, pp 177-190
Antonio Piacentino , Pietro Catrini
Department of Energy, Information Engineering and Mathematical Models, University of Palermo, Viale delle Scienze, Edificio 9, Palermo, Italy

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.

Keywords: Thermoeconomic diagnosis, Evaporator fouling, Direct expansion coil, Exergy, Malfunction cost, Fuel impact, Induced malfunction, Intrinsic malfunction.

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