【正文】 refrigeration plant subjected to a mercially available cold store, a controlalgorithm, based on the fuzzy logic and able to select the most suitable pressor speed in function of the cold store airtemperature, is presented. The main aim is to evaluate the energy saving obtainable when the fuzzy algorithm, whichcontinuously regulates the pressor speed by an inverter, is employed to control the pressor refrigeration capacityinstead of the classical thermostatic control, which imposes on/off cycles on the pressor that works at the nominal frequencyof 50 Hz. The variation of the reciprocating pressor speed is obtained by controlling the pressor electric motor supplycurrent frequency in the range 30–50 Hz, as it is not possible to consider values smaller than 30 Hz because of the lubricationtroubles due to the splash system. In this range, two among the most suitable working fluids proposed for the R22 substitution,such as the R407C (R32/R125/R134a 23/25/52% in mass) and the R507 (R125/R143A 50/50% in mass) are tested. Comparingthe pressor speed fuzzy control with the classical thermostatic control, frequently used in the cold stores and in otherrefrigeration systems, the experimental results show a meaningful energy saving equal even to about 13% when the R407C isused as a working fluid. In particular, to explain from the energy saving point of view the best performances of the refrigerationplant when the pressor speed varies, an exergetic analysis is realized. Besides, with regard to the inverter cost, the paybackperiod determined is more than acceptable for the plant size examined.q 2020 Elsevier Ltd and IIR. All rights reserved.Keywords: Compression system。 Compresseur a` piston。DT222。DT222。 _mref240。cp222。The efficiency defects of the ponents are linked to theexergetic efficiency of the whole plant by means of thefollowing relation:hex188。The efficiency defect has been evaluated for each device ofthe plant, considering the ratio between the exergy flowdestroyed in each ponent and the exergy flow requiredto sustain the process, . the electrical power supplied tothe pressor:di188。cp188。2_Qcotco240。 0–16 A ^% .。 it is lubricated with polyester oil and its speed isregulated by means of a PWM inverter. It is formed by arectifier that converts the threephase main voltage, .380 V, 50 Hz to DC voltage and by an inverter that invertsNomenclatureCOP coefficient of performanceE_x exergy (W)ex specific exergy (J/kg)f pressor electric motor supply frequency(Hz)_Lcppressor power input (W)_m mass flow rate (kg/s)_Q thermal power (W)T temperature (8C)T0environmental temperature (8C, K)t time (s)Tair。 R507Re180。 Regulation。 fax: 254。 thedefuzzification process permits to transform the fuzzyoutput into a defined value. The main difficulty of thefuzzy logic is connected with the necessity of a goodspecific experience in the design and the building of a fuzzycontroller. So, as for the regulating parameters someexperimental considerations have allowed us to set thecontrol variables of the reciprocating pressor speed. It isclear that the choices of the rules and membership functionsof the controller can be properly changed. However, it is tobe considered that it is certainly convenient to control fromthe energy saving point of view the pressor speedbecause it works at lower frequencies, but in this situationthe time required to obtain the setpoint temperature will beTable 1Transducers specificationsTransducer Range AccuracyCoriolis effect mass flow rate meter 0–2 kg/min ^%RTD 100 4 wires 2100 to 500 8C ^ 8CPiezoelectric absolute pressure gauge 1–10 bar。exin。4222。va222。In Fig. 9 a parison in terms of the exergeticefficiency of the whole plant, when the R407C andthe R507 are used, is reported versus the frequency of thecurrent feeding the pressor。5222。ev222。P_ExoutP_Exin188。DT222。gulation。Fuzzy control of the pressor speed in a refrigeration plantC. Apreaa, R. Mastrullob, C. Rennoa,*aDepartment of Mechanical Engineering, University of Salerno, Via Ponte Don Melillo 1, 84084 Fisciano (Salerno), ItalybDETEC, University of Naples Federico II, Tecchio 80, 80125 Naples, ItalyReceived 8 August 2020。 Re180。d240。 this last value is acceptable as itcorresponds to the differential band of a thermostat.To explain the reason for the energy saving obtainablewith a fuzzy control algorithm that allows to regulatecontinuously the pressor velocity in parison with athermostatic control, an exergetic analysis of the ponents of the refrigeration plant has been realized onvarying the pressor speed. For this purpose, it resultsmore correct to realize the exergetic analysis in the steadystate conditions instead of the transient conditions, whichderive from the pressor speed fuzzy control, selectingagain the same conditions in terms of pressor refrigeration capacity. In particular, the refrigeration powercorresponding to each frequency of 30, 35, 40, 45, 50 Hzunder the transient conditions is considered again under thesteadystate conditions to allow a correct measurementprocess. This experimental analysis has been performedrelated to the summer season, with the outdoor temperatureat the condenser kept at about 32 8C, but similar results havebeen obtained also in other working conditions. Inparticular, the tests realized in the winter season verify thecorrect refrigerant lamination when, varying the pressorspeed, the pression ratio across the valve is low.The exergetic analysis allows to obtain importantinformation about the plant total irreversibility distributionamong the ponents. The overall plant exergeticefficiency has been evaluated as the ratio between theexergy output and the exergy input and can be expressed as:hex188。ev2 exout。_Lcp240。8222。240。where T0is