A novel method to measure the energy efficiency and performance of an auto-cascade refrigeration cycle

•A measurement method for auto-cascade refrigeration systems is developed.•The method allows measuring the experimental performance with only eleven sensors.•An auto-cascade with R-600a/R-1150 working at −80 °C was used for model validation.•Uncertainty is below 1% for compositions and 5.2% for cooling capacity and COP.•Calculated COP ranges from 0.14 ± 5.2% at −83.0 °C to 0.277 ± 2.8% at −59.5 °C. Auto-cascade refrigeration systems are the most used cycles to maintain spaces at ultra-low temperature conditions (-80 to −60 °C). The interest in these systems has risen due to the need to maintain and distribute COVID-19 vaccines. However, there is a lack of experimental validation of the theoretical models that are used to analyse and optimize them. In this work, a novel method to calculate the thermodynamic performance, circulating compositions, and energy efficiency of an auto-cascade refrigeration system is presented. The method is based on the measurements of an experimental auto-cascade plant at temperatures from −83.0 to −59.9 °C. The results of the study showed that the proposed calculation method was able to accurately predict the thermodynamic performance, circulating compositions and energy efficiency of an auto-cascade system. The uncertainty of the predictions was found to be below 1% for circulating compositions and 5.2% for the cooling capacity and COP.