The low-temperature transportation of biological products necessitates urgent demands for the cold storage function of portable low-temperature freezers. In this study

experimental tests were conducted to investigate the temperature changes in a Stirling low-temperature freezer with a low-temperature phase change material (PCM) during power failure. Based on the test results

a three-dimensional numerical model was developed to further analyze the effect of the height ratio of the side-swing arrangement of the cold plate on the air temperature in the freezer and the phase transition of the PCM. The experimental results showed that when the ambient temperature was 20 °C

the central temperature of the freezer without the PCM required 0.26 h to rise from -86°C to -70 °C

whereas the central temperature of the freezer loaded with 3.2 kg PCM (EO-75) required 5.33 h to rise from -86 °C to -70 °C. The simulation results showed that the height ratio of the side-swing arrangement of the cold plate had an important effect on the freezer temperature. When the height ratio of the cold plate increased from 50% to 90%

the time of keeping the central temperature at -86 °C to -70 °C was extended from 2.96 h to 7.66 h

and the cooling efficiency of the PCM increased from 29.18% to 48.28%. The height ratio of the cold plate should be 90%. The results of this study can be useful in the research on low-temperature cold chain transportation technology.