On the reliability of thermoeconomic diagnosis of fouled evaporators: assessing the influence of geometries, operating conditions and reference state

Thermoeconomic diagnosis of refrigeration systems is a pioneeristic approach, which has been proven to achieve good performances (under favorable conditions) for the detection of specific faults such as condenser and evaporator fouling and compressor valve leakage. In this paper the sensitivity of performance in detecting fouled Direct Expansion (DX) coils is investigated; the examined parameters are the temperature and relative humidity of coil inlet air and the sensible/latent heat ratio of the coil (varied by considering different numbers of rows). As the thermoeconomic model requires splitting the specific exergy of cooling air into “mechanical”, “thermal” and “chemical” fractions, and since under fouled conditions the evaporator strongly modifies its exergetic performance, it is worthwhile discussing the possible existence of “optimal performance” regions for the use of this diagnostic technique.