An experimental investigation on a modified cascade refrigeration system with an ejector

This paper presents an experimental investigation on a modified cascade refrigeration system (MCRS) with an ejector applied in the first stage cycle. Experiments are conducted in the prototype of an ultra-low temperature upright freezer equipped with MCRS to validate its energy-saving feasibility. The results indicate that the energy consumption for the whole prototype is 11.58 kW · h · 24h^-1, and is 4.77% lower than that of the baseline freezer at the ambient temperature of 25 °C. Furthermore, the effects of the ambient temperature on system performances and the pressure lift ratio and the entrainment ratio of the ejector are investigated. It is found that the pressure lift ratio of ejector increases when the ambient temperature rises, while the entrainment ratio is insensitive to the change of the ambient temperature. This study provides a way to develop the ejector expansion refrigeration technologies applied in ultra-low temperature upright freezer.