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.

Operation performance of an ultralow-temperature cascade refrigeration freezer with environmentally friendly refrigerants R290-R170.

In the present study, the operation performance of an ultralow-temperature cascade refrigeration freezer is experimentally researched. The natural refrigerants R290-R170 are adopted as high-temperature and low-temperature fluids. The experimental test is conducted in a type laboratory with a dry bulb temperature of 32.

A quantitative method for evaluating numerical simulation accuracy of time-transient Lamb wave propagation with its applications to selecting appropriate element size and time step.

Lamb wave technique has been widely used in non-destructive evaluation (NDE) and structural health monitoring (SHM). However, due to the multi-mode characteristics and dispersive nature, Lamb wave propagation behavior is much more complex than that of bulk waves. Numerous numerical simulations on Lamb wave propagation have been conducted to study its physical principles.