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The computation methods of the thermodynamic properties are used for theoretical studies of multicomponent refrigerant blends (MRBs) for low-temperature throttling refrigeration units, providing cryostatting modes for cooled objects in the temperature range of –90 – –160 °С. The article presents the comparative analysis of the state equations for calculating thermodynamic properties of multicomponent refrigerant mixtures. Quantitative and qualitative differences in the results of calculations in the lowtemperature region are determined.

Theoretical studies of refrigerant blends in closed-loop throttling low-temperature refrigeration machines, which provide the specified cryostatting mode for cooled objects in the temperature range of – 90 to – 160°С, require computation of thermodynamic properties and phase equilibria. A method of computation of the phase equilibria and thermodynamic properties of multi-component refrigerant blends is presented based on the use of the two-parameter Redlich–Kwong equation of state in the Soave modification.

The article presents a description of a new method of calculation by means of which the distribution of the temperature of a mixture of coolants along the working circuit of a low-temperature refrigerating machine may be calculated to a first approximation and the quantitative composition of a charge mixture of coolants determined for a given composition of the circulating mixture of coolants.

Results of experimental research of low-temperature multicomponent mixed-refrigerant throttling refrigerator are given. Appliance of refrigerator in new domestic-made ultralow-temperature freezer for cryoconservation and long-term storage of medical and biological objects at temperature minus 150°C is described. Within experimental research, test bench with development prototype of ultralow-temperature medical freezer is made. Experimental and theoretical studies are compared. Availability and amount of local composition shift is defined. Ways to improve simulation model and increase energy efficiency of cryostatting systems are determined.