The paper presents the experience and methodological aspects of application of computational fluid dynamics (CFD) for quick correction of the flow path of a twostage centrifugal compressor. A rated efficiency of the compressor is not obtained because of a nonoptimal design of the flow section completed by a producing plant. The fact that it is impossible to vary the main geometric parameters of stages limited by dimensions of a compressor casing and blanks complicated the task to improve the flow path. The theoretical and numerical study of feasibility to replace vaneless diffusers with vaned ones was carried out. The results of investigation led to the conclusion that the operation of the compressor with vaned diffusers was poor due to the fact that optimal gasdynamic relations needed for operation of stages with vaned diffusers couldn’t be provided. Using a numeric modeling the major elements limiting the efficiency of an initial flow path with vaneless diffusers were defined. The measures to optimize the stage elements using a computational fluid dynamics were undertaken. A genetic algorithm of automatic optimization implemented in the Numeca Fine/Turbo software package was used. The main result of the work consisted in that the layout of the compressor with vaneless diffuser providing the COP increase by 1.6% as regards the basic variant was analyzed. Moreover, the implying to accelerate considerably the modeling of hydraulic flow path of the compressor (without spacing and labyrinth seals) with the introduction of corrections for disc friction and internal leaks by estimating the given values from the primary calculation was examined.

To cool damaged areas of tissue in order to achieve a fast analgesic effect the applying a thin film of a boiling gas mixture at temperature Т0 = 273…238 К is widely used. It is easy to obtain such a temperature by using a cooling aerosol. The experimental data on temperature distribution on the cooled surface during throttling of a propanebutane mixture from 0.1; 0.5; 1.00 mm nozzles to Т0 = 240; 248; 258, 263 К level, applied in sports medicine, were obtained. Flexible capillary tubes at 120 mm outer diameter and 50 mm wall thickness to be used in local cryotherapy and cryosurgery were studied.