Vol 109, No 3 (2020)

The paper envisages the results of calculation of a threedimensional viscous flow in 18 lowflow stages of centrifugal compressors in the range of optimal conditional flow coefficient Фopt = 0.007-0.018. Gasdynamic characteristics of the internal and polytropic pressure coefficients in full parameters were plotted and compared with experimental data. The calculated gasdynamic characteristics of viscous flow satisfying the engineering accuracy of calculations and experimental character of the curves were obtained using Ansys CFX software

The paper presents the results of mathematical modeling and experimental research of the effect of a heataccumulating wall with a water heat exchanger on building cooling. The first part describes the mathematical model of the building. The modeling was carried out using the TRNSYS program that allowed computing an hourly load of cooling the heataccumulating walls with a water heat exchanger for the purpose of subsequent comparison with the cooling load of a sample room. The building modeling scheme, the heat network model, and the method of calculating the total thermal resistance of the thermosetting wall layer are given as well

The results of study of effect of freezing temperature on the change of amino acid content and the ratio of essential and nonessential amino acids in veal proteins are given. The meat of calves at the age of 3 months, bred in the Leningrad region of the RF, was the object of research. The amino acid composition of veal proteins was analyzed using the Shimadzu 20AD Chromatograph with precolumn phenylisothiocyanate derivatization and spectrophotometric detection at 254 nm by reversedphase gradient highperformance liquid chromatography (HPLC). The Kjeldahl method was used to define the protein content on the basis of the sample mineralization. It was shown that the change of the amount and ratio of essential and nonessential amino acids of veal proteins depended on the freezing temperature as well as on structural features of Rside radicals. Also it was established that the total amount of essential and nonessential amino acids in veal proteins during freezing at -24 and -35 °С temperatures decreased by 13,5 and 8,2%, respectively; the total of essential amino acids by 11 an 7%, nonessential ones by 22 and 11%, respectively. It was proved that significant changes were characteristic of amino acids with polar anionic and cationic radicals. So, the amount of amino acids with polar negatively charged radicals during veal freezing at temperatures -24 and -35 ° С decreased by 22 and 16,5%; with polar positively charged radicals - by 17 and 13,5%, respectively. At the same time, the freezing temperature affects slightly the change in the content of amino acids with nonpolar (hydrophobic) Rgroups and polar nonionogenic radicals. It was shown that the total amount of free amino acids increased independently of the freezing temperature. However, more essential amino acids were accumulated in veal frozen at a temperature of -24 ° С (2,33 times) than at -35 ° С (1,80 times). The amount of free nonessential amino acids changed to a lesser extent