Vol 108, No 11 (2019)

Научноконсультативная группа Саммита по изменению климата 2019 представила доклад United in Science, где собраны ключевые научные результаты новейших работ, выполненных основными организациями, ведущими исследования в области глобального изменения климата, включая Всемирную метеорологическую организацию (ВМО), Программу Организации Объединенных Наций по окружающей среде (UNEP), Глобальный углеродный проект, Межправительственную группу экспертов по изменению климата [IPCC (МГЭИК)], сети «Земля будущего» и «Лига Земли», Глобальную рамочную основу для климатического обслуживания (ГРОКО). United in Science - это обобщение ключевых выводов из нескольких более подробных докладов названных организаций.

Ceteris paribus the efficiency of heat pumps is higher in the systems with moderate temperature levels for heat consumers. Lowtemperature systems for heating and hot water supply are considered the most promising. The lowtemperature airwater heat pumps consist of a circuit, through which a refrigerant circulates, an evaporator, a condenser and a compressor. The selection of a scroll compressor for a lowtemperature heat pump is defined by its operating characteristics which include isentropic efficiency, feed coefficient and compression ratio. To demonstrate/prove the manufacturer’s specifications for scroll compressors the authors investigated the compressors of three manufacturers Copeland, Danfoss and Invotech: lowtemperature compressors ZF15K4TTFD, LLZ015T4A, YF35E1G100 and mediumtemperature ones ZB29KCETFD, MLZ030T4 and YM70E1G100. The study of lowtemperature compressors was carried out in the range of refrigerant boiling temperatures from minus 10 to minus 40 оС, medium temperature scroll compressors in the range from 0 to minus 30 оС. The dependences of the isentropic efficiency and the feed ratio of a scroll compressor on the compression ratio were defined. The data obtained allowed plotting diagrams of respective dependences for various compressor models.

The paper concludes the results of computing the parameters of contact interaction of rough surfaces of friction. The microgeometry of the surfaces was simulated using Gaussian random fields, the statistic characteristics of which were determined by the results of profilogram processing. The force of contact interaction of elastic surfaces was calculated by solving the Hertz problem of point contacts. The dependences of the contact area, coefficients, the volume of the contacting material, and the surface interaction force on the generalized parameter of roughness for pairs of friction steelsteel and steelbronze are cited. The results of a computational study of the contact surface interaction made it possible to estimate the limits of friction regimes depending on the surface microgeometry and specific load on supportingsealing assemblies.

The results of the experiment and simulation of the process of wet soil freezing are presented. The comparison of the experiment and simulation gives satisfactory results. The initial temperature of soil is +20 °С. The temperature of stabilizer is constant and equal to -20 °С. The soil moisture is 0.2 kg of water per 1 kg of dry soil. The experimentally measured speed of movement of the freezing front of wet soil is 6.25 mm/day. The designing speed is 7.4 mm/day. The simulation was carried out on the basis of the differential equation of nonstationary heat conductivity written for a cylindrical wall under the corresponding initial and boundary conditions.