【正文】 8222。240。_Lcp240。where T0is the environmental temperature while Tmt。ev2 exout。co2 exout。 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。 1–30 bar ^。d240。39089964037.Email address: (C. Renno).[1,2]. This method of refrigeration capacity control, whichconsists in varying the pressor speed to continuouslymatch the pressor refrigeration capacity to the load, hasbeen analyzed during the last years [3–10]. An inverter canbe used to regulate the pressor speed. There are differenttypes of electronic variablespeed drives, but the pulsewidth modulated source inverter (PWM) is the most suitablefor its low cost and high efficiency. The application of thistype of control of the refrigeration capacity to a mercialpressor, though presents some advantages in terms ofenergy saving, determines some disadvantages such as theinverter cost and some troubles linked to the pressorlubrication and reliability [11,12] and to the correct workingof the expansion devices. This last problem is negligiblewhen the secondary fluids at the heat exchangers are in gasphase, as in the plant examined, but it seems to beremarkable when the secondary fluids are in the liquidphase [13]. So, the primary aim of this paper is to setup acontroller capable of regulating continuously the speed of areciprocating pressor frequently used in cold stores andin other small size refrigeration systems whose this type ofpressor generally has no oil pump. This kind of controlallows us to match the pressor refrigeration capacity tothe cooling load at any time, so that the pressor can alsowork at other frequencies smaller than 50 Hz. It is to beconsidered that with the classical thermostatic controlfrequently used in the cold stores and in other small sizerefrigeration systems, the pressor works only at 50 Hz.In particular, referring to a vapor pression refrigerationplant subjected to a mercially available cold store, acontrol algorithm based on the fuzzy logic, and able to selectthe most suitable pressor speed in function of the coldstore air temperature, is presented in this paper. Apart fromthe fuzzy logic, the pressor speed control might also beobtained by means of other techniques such as thetraditional proportionalintegral and derivative control(PID) [14–18]. In particular, the fuzzy control logic,pared with PID, allows both to use better theexperimental knowledge related to the trend of the variableswhich characterize the working of the refrigeration plantand to adopt a control logic based on a nonmathematicalmodel, and hence to avoid the determination of the specificmodels of the refrigeration plant ponents [19–21].Moreover, a fuzzy controller with respect to PID controlgenerally might allow obtaining performances parableor sometimes better in terms of precision of the set pointrequired. Besides referring to a fuzzy controller theovershoot of the variables is small and the settling timefast as regards the dynamic response during the suddenvariations in the cooling load。 Re180。 Fuzzy logic。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。 R407C。gulation。 all this generally results in arobust control [22–24]. So, experimental tests have beenconducted to pare the plant performances obtainableusing as pressor refrigeration capacity control systems,both the fuzzy algorithm and the classical thermostat thatdetermines onoff cycles of the pressor that works at afrequency of 50 Hz. The working fluids tested, the R407C(R32/R125/R134a 23/25/52% in mass) and the R507 (R125/R143A 50/50% in mass), are among the most diffusesubstitutes of R22.2. Experimental plantThe vapor pression experimental plant, subjected toa mercially available cold store and shown in Fig. 1,ismade up of a semihermetic reciprocating pressor, an aircondenser followed by a liquid receiver, a manifold withtwo expansion valves, a thermostatic one and a manual onemounted in parallel, to feed an air cooling evaporator insidethe cold store. The pressor, as declared by themanufacturer, can work with the fluids R22, R507 andR407C。DT222。 ^ Wattme