The paper presents the results of theoretical and experimental analysis of a vacuum-freeze-drying refrigeration machine based on carbon dioxide. Such refrigeration machines can be equipped with refrigerators for the needs of medicine, where low temperatures are widely in demand in the range from minus 80 degrees Celsius to minus 130 degrees Celsius. The problem of developing alternative refrigeration machines is dictated by modern environmental requirements for working substances, which are gradually being tightened and soon the use of familiar freons will become impossible. For the air conditioning and commercial refrigeration industry, new substances are being actively developed, such as hydrofluoroolefins (HFOs), hydrocarbons can also serve as substitutes for hydrofluorocarbons and their mixtures, but it must be considered that they are combustible and explosive. A carbon dioxide vacuum sublimation unit may be an alternative to modern freon vapor compression refrigeration units for the indicated temperature range, but subject to comparable energy costs during its operation. The article examined the three-stage and four-stage cycles of a vacuum-freeze-drying refrigeration machine, conducted their theoretical comparison in terms of COP with a cascade cycle on hydrocarbon working substances. It can be noted that the COP of the considered cycles are close, but the environmental friendliness, safety and non-combustibility of carbon dioxide gives the advantages of a vacuum freeze-drying refrigeration machine.

Despite the high urbanization in the world, at the level of 55% in Europe and the USA, there is still a culture of home gardening in cities, both for decorative purposes and for growing crops for consumption in the household. This tradition is favored by the prevalence of low-rise buildings, whose share in the USA is 92%, in Europe 80%, in Russia only 52%. Due to the lack of access to land, the inhabitants of Russia need new approaches to crop production, which will allow access to fresh vegetables at home, such methods can be aero and hydroponic plants that allow growing plants without soil, and these plants can be easily automated. Due to the specifics of the housing stock in Russian cities, a balcony or a loggia was determined as the best place for installing personal farms. The balcony or loggia are unheated rooms of the apartment, redevelopment with the balcony or loggia attached to the room or the transfer of heating devices is prohibited, therefore, to arrange optimal conditions for plants, along with warming, this room must be heated. Calculations showed that to maintain the required temperature on the insulated The balcony of an apartment building in Moscow will require 7488 MJ of thermal energy for the entire heating period. The cost of electricity costs per year, when using a heat pump, can be reduced by more than 35% compared to electric heating, and the energy consumption during conditioning is also taken into account in the total cost of heat supply using a heat pump, which allows you to create more favorable temperature conditions in summer.

The paper considers the low refrigeration capacity ammonia refrigerating machine. New technical solutions are proposed to decrease ammonia capacity, to scale-up the operating safety and to provide self-acting unsupervised automatic mode. The method of constructing a mathematical model and analysis of the refrigeration machine operation is described.

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