Experimental Investigation on Intermittent Operation Characteristics of Dual-Temperature Refrigeration System Using Hydrocarbon Mixture

Abstract

An experimental rig of a zeotropic mixture separation condensation-based dual-temperature refrigeration cycle is built and the mixture R290/R600a is used as the refrigerant. Compared with a conventional cycle, the proposed refrigeration system demonstrates its application advantages under an on–off operation mode. Furthermore, the on–off periodic operation behaviors of this refrigeration system are experimentally investigated. The influence of a different refrigerant charge, a refrigerant mass fraction, a throttling valve opening, and ambient temperature are explored to evaluate the cyclic operation characteristics. The results reveal that the compressor average power for the duration of the compressor startup increases and the compressor duty cycle first declines then increases with the rise of the refrigerant charge. The average compressor during an on-period decreases from 104.5 W to 79.2 W and meanwhile the compressor duty cycles fluctuates between 72.1% and 96.9% as the R600a-charged concentration increases from 30% to 70%. The average power of the compressor during the on-period and the duty cycle are also sensitive to the freezer valve opening variation. Thus, the minimum energy consumption of 1.60 kWh·24 h−1 is achieved at the refrigerant charge of 300 g, a R600a-charged mass fraction of 50%, and a freezer throttling valve opening of 10%. A higher ambient temperature deteriorates heat transfer during condensation and increases the cabinets’ heat load, the compressor duty cycle, and eventually affects the daily power consumption. Generally, the present study offers an in-depth insight of cyclic operation characteristics of a separation condensation-based hydrocarbon mixture dual-temperature refrigerator under two parallel evaporators’ concurrent cooling process.