【正文】 at the output of the inverter the voltage is adjustable in frequency and magnitude. The manifold with both valves has been mounted to solve possible troubles, because the expansion valves behavior, when the pres sor speed varies, is unknown [13]. The expansion valves used are specifically designed for the R407C and R507. In the evaporation temperature range 220 to 10 8C at a 30 8C condensing temperature, working with the R407C at the nominal frequency of 50 Hz, the pressor refrigeration capacity varies in the range kW. To fix the air temperature on the condenser and to simulate the external conditions, the air ?ows under the in?uence of a blower in a thermally insulated channel, where some electrical resist ances are located. To exactly obtain the same temperature fixed for the air, a regulator is used to control the electrical resistances supply. In some experimental tests, the cooling load in the cold store is simulated by means of some electric heaters linked to a regulator and the electric power is measured by means of a Wattmeter. Table 1 lists the specifications of the transducers used. The test apparatus is equipped with 32 bit A/D acquisition cards linked to a personal puter allowing a high sampling rate and a monitoring of all the measures carriedout by means of the transducers. The data acquisition software has been realized in a Labview environment and the R407C and R507 thermodynamic properties have been evaluated using a 641 dedicated software that has also been used to determine the energy and exergy balances. 3. Experimental procedure description To evaluate the plant performances when an inverter is used, it is necessary to pare the plant energy consumption when the refrigeration capacity is regulated by on/off cycles of the pressor that works at a supply current frequency of 50 Hz, and when the refrigeration capacity is controlled by the fuzzy algorithm. In the experimental tests, different types of cooling loads have been considered. First of all some experimental tests when the cooling load is due both to the periodic opening of the cold store door and to the inevitable heat exchanges with outdoor air, even when the cold store door is closed, have been realized. These tests have been performed at various temperature levels for the air in the coldstore and, precisely, at 5, 0 and 25 8C, opening the cold store door every 20 min for about 5 min with an outdoor air temperature of about 18 8C. Moreover, in some test。 all this generally results in a robust control [2224]. So, experimental tests have been conducted to pare the plant performances obtainable using as pressor refrigeration capacity control systems, both the fuzzy algorithm and the classical thermostat that determines onoff cycles of the pressor that works at a frequency of 50 Hz. The working ?uids tested, the R407C (R32/R125/R134a 23/25/52% in mass) and the R507 (R125/ R143A 50/50% in mass), are among the most diffuse substitutes of R22. 2. Experimental plant The vapor pression exper mental plant, subjected to a mercially available cold store and shown in Fig. 1, is made up of a semihermetic reciprocating p sor, an air c ndenser fol owed by a liquid receiver, a manifold with two expansion valves, thermostatic one and a ual one mounted in parallel, to feed an air cooling evaporator inside the cold store. The ressor, as d clared y the manufacturer, can work with the ?uids R22, R507 and R407C。 these emis sions can be reduced by improving the energy conversion efficiency of the above mentioned systems . A theoretical parison of various refrigeration capacity control methods in full and partload conditions shows that the pressor speed variation is the most efficient technique 01407007/$ see front matter q 2021 Elsevier Ltd and IIR. All rights reserved. doi: 21 640 Nomenclature C. Aprea et al. / International Journal of Refrigeration 27 (2021) 639648 in other small size refrigeration systems whose this type of pressor generally has no oil pump. This kind of control _ T T0 t Tair。 fax: 254。 R507 1. Introduction The vapor pression refrigeration plants, though designed to satisfy the maximum load, work at partload for much of their life generally regulated by on/off cycles of the pressor, working at the nominal frequency of 50 Hz, * Corresponding author. Tel.: 254。 Logique ?oue。 Re180。 Compresseur a` piston。s: Syste`me a` pression。un presseur d39。 R507 Re180。 Fuzzy logic。 Variable speed。 Cold room。 received in revised form 18 December 2021。 不分明集 Syst 1995 年 。 HVAC Res 1997 年 。 Int J 冷藏 2021 年 。 30 (7/8) ： 135– 46. [21] Srinivas MN， Padmanabhan， Chandramouli。 空氣冷卻了管飛翅擴(kuò)展閥門控制定律的蒸發(fā)器模型。 Appl Therm Engng 2021 年 。 Appl Therm Engng 1996 年 。 33– 4. [18] Qureshi TQ， S