HFC refrigerant mixtures are widely used now in cold supply and air conditioning systems. R404А, R410A, R407С are the most popular of them. But the list of HFC refrigerant mixtures is not limited by these refrigerants. The paper envisages the properties, fields of application, environmental characteristics of HFC refrigerant mixtures that are not well known. The statutes of EU regulations ЕС 517/2014 on phasing out of fluorinecontaining gases by 2030 are cited. A diagram presentation of the values of refrigerant mixtures GWP in comparison with R134a is given. It is recommended to replace refrigerant mixtures at high GWP with R134a during an interim period until HFO refrigerants are tested, studied on safety and price reducing.

At present the description of a heat and mass exchange under conditions of the frost formation at the level of cryogenic temperatures is urgent and still littlestudied. The most important for engineering practice in this case is the analysis of the thickness increase of the frost layer. Based on the experiments carried out the authors describe the main features of the frost formation on the wall at cryogenic impact linked with high temperature gradients and air moisture content both in the volume and near the frost surface. The dependences describing the dynamics of growth of the frost layer thickness are offered; they are compared with reliable experimental data. A satisfactory accuracy of dependences to conduct engineering calculations when designing the cryogenic equipment was shown. Based on the analysis of the dynamics of the frost layer growth the authors suggest a particular scheme of grouping panels of atmospheric gasifiers of cryoproducts that allows suppressing the increase of cryosediment on the working surfaces.

The paper presents the results of the experimental study of the stage of a radial axial centripetal turbine at 1,3 kW capacity to drive a highfrequency electric generator at 1 kW nominal capacity that is a part of the plant operating on the organic Rankine cycle. In cryogenic engineering a considerable volume of data on design of centrifugal radial axial lowtemperature turboexpanders at capacity from 100 W to 1MW at 10,000-500,000 rpm with 15-500 mm runner outer diameter and expansion ratio up to 30 in one stage has been accumulated. This experience was used when developing a compact highspeed turbomachine. The major geometric proportions of the turbine setting were defined on the base of the experience of the cryogenic turboexpander design. The paper cites the results of calculations and experimental study of supersonic flow in the distributor and the turbine runner stage. Analytical calculations of the turbine stage efficiency and the results of detailed numerical modeling agree well with the experiment data confirming by that the miniturbine COP at a level near to 75%.

The question of production of cultured ice cream as a synbiotic product (namely containing proand prebiotics) has been raised in connection with the importance of addition of ingredients to foodstuffs including proand prebiotics influencing positively the human organism. Probiotics in cultured ice cream are presented by live cultured milk microorganisms. It is possible to make symbiotic ice cream by additional introducing prebiotics into a product. The introduction of the most widely distributed and used prebiotics such as lactulose, inulin and oligosaccharides was grounded in the paper [8]; their impact on the final product characteristics and survival rate of fermentation bacterial cultures was analyzed. The data analyzed showed the possibility to enhance the nutritive value of cultured ice cream by introducing prebiotics that will contribute increasing consumer demand.