Experimental study on a -86 °C cascade refrigeration unit with environmental-friendly refrigerants R290-R170

Ultralow-temperature refrigeration faces significant issues linked to the security of the cold chain for the production, storage, transportation, and distribution of COVID-19 vaccines. The use of environmentally friendly refrigerants in cascade refrigeration systems (CRS) to provide low-temperature range is motivated by the high demand for ultralow-temperature refrigeration units. In the current study, a CRS is built to generate a low temperature of -86 °C for the storage of COVID-19 vaccines. In the CRS, the natural refrigerant combination R290-R170 is used as high-temperature and low-temperature fluids. The pull-down performance of the -86 °C freezer is explored experimentally, and the stable operating performance is determined at two different dry bulb and wet bulb temperatures. Various status monitors are set up to analyze the CRS's operation features, and several temperature monitors are put in the freezer to analyze temperature variations. The power consumption of the CRS is examined and evaluated. Finally, several key findings are summarized. The current work is the first to involve experimental measurements on -86 °C temperature generated by a CRS, which can substantially enhance experiment data in ultralow-temperature refrigeration and contribute to a more in-depth understanding of the operation performance of a -86 °C ultralow-temperature freezer.