On the reduction of hydraulic resistance based on the hydrophobization of functional surfaces

Analysis of various studies has shown that one of the most promising ways to reduce hydraulic resistance in pipelines during transportation of liquid fluid is a method based on changing the wettability of functional surfaces, i.e. hydrophobization. This paper presents the results of experimental studies of the effect of hydrophobization of pipe surfaces on hydraulic losses. For this purpose, experimental tube samples of steel (20Kh13) were made, on the surface of which a spiral relief was formed using laser equipment, resulting in a hydrophobic state, and the value of the contact angle was 160.7°. From the analysis of the results of experimental studies, the dependence of hydraulic resistance on Reynolds number was obtained, from which it follows that the use of hydrophobic surfaces during water transportation helps to reduce the hydraulic resistance to 9.7%.

Methodology for Calculating Heat Loss in the Study of Friction Stir Welding

Currently, the most promising high-tech and productive process is friction stir welding. An important element of this technology is the determination of the material temperature in the stir zone, which can be determined by calculation based on the amount of heat input introduced into the welding zone. To determine this value, experimental of the dependence of heat input on the tool rotation speed and welding speed were carried out. For this, a scheme of experiments has been selected in which the material to be welded (aluminum alloy AMg5) is modeled as an experimental tube with a diameter of 20 mm, and the tool (made of tool steel R6M5) is modeled as a working plate. On the designed and manufactured stand, studies of the dependence of the heat-liberation value for the speeds of rotation of the experimental tube 42-105 rad/s were carried out. In this case, due to the pressing force of the experimental tube and the working plate, a constant temperature of the place of friction was maintained. The obtained experimental data were used to calculate the heat-liberation value and heat power on each concentric ring 2 mm wide at the end of the working tool with a diameter of 20 mm, as well as the total heat power for different speeds of rotation and welding.When carrying out experiments on the bench, heat losses were determined by thermal conductivity along the rod on which the experimental tube is fixed, as well as from the working plate made of tool steel through the gasket onto the working table and by convection from the surface of the rotating experimental tube into the environment. The calculation results showed that each of these losses does not exceed 3-10%. These losses are taken into account in the heat supply calculations.

Research of Heat Power in Friction Stir Spot Welding

Nowadays the most perspective, high-tech and productive process is friction stir spot welding. The most important part of this technology is to determine the temperature of the material in the stir zone. This parameter is easily counted by the amount of the heat input, put in the welding zone. We made experimental researches about the relation of the heat power, therotation speed and the diameter of the working tool. For that purpose an experimental scheme was chosen, which models a welding material (aluminum alloy AMg5) as an experimental tube 20 mm in diameter. The tool (shear steel P6M5) is modeled as a working plate. Measurements of the frictional moments depending on the rotation speed of the experimental working tube during the constant temperature are made on the prepared stand. By the experimental data the specific heat input and the heat power were counted on every concentric ring, 2 mm in width, in the end of the working tool, 20 mm in diameter. Also, the sum of the heat power for the whole tool during various rotation speed terms was counted too. On the stand throughout the experiment were determined all the thermal conductivity heat losses along the rod, which the experimental tube was pinned on, all the working plate heat losses through the gasket towards the working desk and the convection from the surface of the rotating experimental tube to the environment. According the data, any of these losses is from 3 to 10 percent. This is shown in the heat input counting.

Research of Heat Input in Friction Stir Welding

Nowadays the most perspective, high-tech and productive process is friction stir welding. The most important part of this technology is to determine the temperature of the material in the stir zone. This parameter is easily counted by the amount of the heat input, put in the welding zone. We made experimental researches about the relation of the heat input, therotation speed and thediameter of the working tool. For that purpose an experimental scheme was chosen, which models a welding material (aluminum alloy AMg5) as an experimental tube 20 mm in diameter. The tool (shear steel P6M5) is modeled as a working plate. Measurements of the frictional moments depending on the rotation speed of the experimental working tube during the constant temperature are made on the prepared stand. By the experimental data the specific heat input and the heat power were counted on every concentric ring, 2 mm in width, in the end of the working tool, 20 mm in diameter. Also, the sum of the heat power for the whole tool during various rotation speed terms was counted too. On the stand throughout the experiment were determined all the thermal conductivity heat losses along the rod, which the experimental tube was pinned on, all the working plate heat losses through the gasket towards the working desk and the convection from the surface of the rotating experimental tube to the environment. According the data, any of these losses is from 3 to 10 percent. This is shown in the heat input counting.

STUDY OF FREON R22 HEAT TRANSFER IN FLOODED EVAPORATORS AT LARGE FREON REFRIGERATING TURBOMACHINERY

The object of research includes the experimental evaporator, the model of a large Freon refrigeration plant, and technical-grade Freon R22. The purpose of the research is to assess the effect of the tube bank lane and regime parameters (saturation pressure and saturation temperature) on heat transfer during technical-grade Freon boiling in multi-row tube banks, as well as to continue studying the features of freon boiling processes in the evaporators of large refrigerating machines. The article shows the calculated dependences of the influence of regime parameters on heat transfer in the process of boiling Freon R12 and R22 in flooded evaporators with great height of experimental tube bank. The visual observations of the boiling process have been described. Calculated dependences of heat transfer along the tubes in the tube bank have been obtained, the character of heat transfer changes and temperature distribution according to the height of the tube bank has been defined.