Vol 106, No 10 (2017)

In connection with imposing a ban on high GWP refrigerants use the interest is growing to the use of natural refrigerants, in particular carbon dioxide, in refrigerating plants. There are several circuits of CO2 refrigerating plants. The paper examines a cascade refrigerating plant with CO2 in the lowstage part and with R134а in the upperstage part. A basic circuit and refrigerating cycle are cited. A cascade cycle was analyzed for adopted initial conditions that provide the supply of needed cold to consumers of lowand average temperatures using the entropy and statistical method of analysis (ESMA). A sequencing of calculation is given as well as the formulae and results of calculation of all necessary values to specify energy losses through components of the cascade system. The data are compared with the losses through components of other СО2 and R404А systems. The power efficiency of all systems was compared as well, and the comparison proved the advantage of the R744/R134а cascade system.

An improved method of calculation of a cryogenic freezer to freeze smallfruited products of vegetable origin and smalllump products of animal origin is examined. This method is intended for designing a cryogenic freezer that uses liquid nitrogen as a refrigerant, and the method may be used at the enterprises applying the technology of cryofreezing of smallfruited products of vegetable origin as well as smalllump products of animal origin. An example of calculation of the cryogenic freezer of given capacity is presented. Pineapple guava fruits were chosen as a basis object for cryofreezing. The calculation of the apparatus begins with determination of initial data (characteristics required), then the selection of the apparatus construction materials, the calculation of a drum and a conveyor belt, the calculation of drive, insulation, shaft fit on the drum etc. are performed.