【正文】 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。 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。 Cold room。 Piston pressor。 Variable speed。 Regulation。 Fuzzy logic。 R407C。 R507Re180。gulation a` logique floue de la vitesse d’un presseurd’une installation frigorifiqueMotscle180。s: Syste`me a` pression。 Chambre froide。 Compresseur a` piston。 Vitesse variable。 Re180。gulation。 Logique floue。 R407C。 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。 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。39089964327。 fax: 254。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