【正文】 y examples offuzzy control can be found in some recent applications. Inparticular, in the heating ventilation and airconditioningindustry there are various fuzzy control applications of theair temperature and humidity [25–28]. The design of afuzzy controller requires three essential phases. The first isto establish the input and output variables. The second is todefine the membership functions for the input and outputvariables. The last is to select or formulate the control rules.The main goal of this paper is to determine a fuzzycontroller capable of regulating the pressor electricmotor supply current frequency. In Fig. 2 a block diagram ofthe fuzzy control process of the mercially avalaible coldstore air temperature is reported. In particular, the figureshows a twoinput oneoutput fuzzy controller. The inputvariables are the temperature difference between the setpoint temperature and the real temperature of the air in thecold store 240。cscold store air temperature (8C)Tsetsetpoint temperature (8C)Greek symbolsd efficiency defecth efficiencyDh enthalpy variation (J/kg)DT temperature difference (8C)t dimensionless exergetic temperatureSubscriptsco condensercp pressordes destroyedev evaporatorex exergeticin inletis isentropicmt mean thermodynamicout outletref refrigerantC. Aprea et al. / International Journal of Refrigeration 27 (2020) 639–648640the DC voltage to a three phase AC supplyvoltage to thepressor motor。 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。 fax: 254。 these emissions can be reduced by improving the energy conversionefficiency of the above mentioned systems. A theoreticalparison of various refrigeration capacity controlmethods in full and partload conditions shows that thepressor speed variation is the most efficient technique01407007/$ see front matter q 2020 Elsevier Ltd and IIR. All rights reserved.doi:International Journal of Refrigeration 27 (2020) 639–648*Corresponding author. Tel.: 254。 R407C。gulation。 Vitesse variable。 Chambre froide。gulation a` logique floue de la vitesse d’un presseurd’une installation frigorifiqueMotscle180。 R407C。 Regulation。 Piston pressor。 accepted 18 February 2020AbstractIn this paper, referring to a vapor pression 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。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。 received in revised form 18 December 2020。 Cold room。 Variable speed。 Fuzzy logic。 R507Re180。s: Syste`me a` pression。 Compresseur a` piston。 Re180。 Logique floue。 R5071. IntroductionThe vapor pression refrigeration plants, thoughdesigned to satisfy the maximum load, work at partloadfor much of their life generally regulated by on/off cycles ofthe pressor, working at the nominal frequency of 50 Hz,imposed by a thermostatic control which determines a highenergy consumption. Moreover, the inefficient use ofelectricity to supply the refrigeration and airconditioningpressors is considered as an indirect contribution to thegreenhouse gases emitted in the atmosphere。39089964327。39089