A. V. Paleshkin, V. V. Terent′ev, UDC 629.78 and S. O. FirsyukA methodological approach to determination of the thermal state at a point on the surface of an isothermal element of a small spacecraft has been developed. A mathematical model of heat transfer between surfaces of intricate geometric confi guration has been described. In this model, account was taken of the external fi eld of radiant fl uxes and of the differentiated mutual infl uence of the surfaces. An algorithm for calculation of the distribution of the density of the radiation absorbed by surface elements of the object under study has been proposed. The temperature fi eld on the lateral surface of the spacecraft exposed to sunlight and on its shady side has been calculated. By determining the thermal state of magnetic controls of the orientation system as an example, the authors have assessed the contribution of the radiation coming from the solar-cell panels and from the spacecraft surface.The most diffi cult thing about mathematical modeling of heat transfer of a nonhermetic spacecraft (sp) is to determine the external and internal radiant heat transfer. In engineering practice, there is a great need for a universal and rather userfriendly model of external and internal radiant heat transfer of a spacecraft. Considering the exterior and interior surfaces of the spacecraft as an aggregate of a fi nite number of isothermal elements, we determine the density of the radiant fl ux incident on each of these elements under the following conditions:(1) the spacecraft can be in an assigned fi eld of radiant fl uxes coming from the sun and, if the craft is on a low circumplanetary orbit, from the planet; (2) the spacecraft surfaces in heat transfer can have an intricate geometric confi guration, as a result of which there is a possibility for mutual occultation of some surfaces from the radiation of external sources of radiant fl uxes and from the radiation of the surfaces of the spacecraft itself; (3) within each isothermal element (portion of the spacecraft surface), the radiation characteristics of the surface must be uniform.The problem of radiant heat transfer was solved under the following simplifying assumptions:(1) the surfaces taking part in the heat transfer are diffuse-type, i.e., the directed emissivity factor and directed absorptivity of these surfaces, do not depend on the direction; (2) the surfaces are gray in two characteristic spectral ranges: in the range of wavelengths from 0.2 to 2 μm, where practically all the energy of solar radiation is concentrated, and in the range from 5 to 50 μm, in which there is a release of most of the energy of self-radiation of bodies having a moderate temperature at the level of 200-500 K; (3) within each portion of subdivision of the spacecraft surface into isothermal elements, the density of the incident radiation fl ux is uniform on the portion′s surface.

Agricultural machines engaged in crop production, are used in cycles, and short-term from mid-spring to mid-autumn, and the rest for long periods in storage. The article deals with improving the reliability and extending the service life of machinery and equipment for agricultural purposes. Improving the reliability of machines and equipment of agricultural purpose is achieved by preventing metal corrosion during the long storage and the term of use is performed by maintaining and controlling the temperature and humidity of air in a sealed shelter. To prevent condensation on the surface of the equipment and the shelter is encouraged to pursue their heating infrared radiators to a temperature above the temperature of formation of the dew point. Infrared emitters installed in the air gap between object technology and a domed cover, and connected with the control unit, having in its composition sensors monitoring temperature and humidity under the cover. The uniform distribution of infrared radiation over the surface of the object storage is provided by a symmetrical placement of the sources of infrared radiation, and used as a material of the cover of insulated material with high reflectivity. The proposed method of storage of machinery and equipment limits the heat transfer between the machine and the environment. Due to the fact that a protective cover can make the desired protective properties (reflectivity, conductivity, limiting convective heat transfer) is the effect of limiting the speed of heat transfer, which avoids extreme temperatures, under which condensation may form on the surface of agricultural machines. As a material of the protective cover you can use modern insulating materials.

The principle of automated construction of a fan blade model according to the profile measurements performed in a CAD-system is presented. Automatic construction of the model is based on the results of measurements obtained in the course of the control measurement procedure. The process of the blade airfoil control with the use of a portal-type Coord3 Hera NT coordinate-measuring machine and a measuring head with a Renishaw PH10T probe is described. The main points of the check method and instrumentation measures are presented. For example, the principle of the fan blade fixing is considered, the process of measuring the position of the base surfaces and points is presented, the process of measuring the profile points coordinates is described, the geometric parameters obtained in the course of calculation of profile deviations are presented. A measured 3D model of the fan blade is created according to the data of the control measurement procedure, taking into account complementary construction tools. The order of work for the automation of constructing a three-dimensional blade model is described. The direction of further work is specified, related to carrying out strength calculations to create a hot model of the measured blade, and subsequent aerodynamic calculations of the resulting blade to determine the most efficient set of geometric parameters for robust optimization.

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