Imparting hydrophobic functionalities to copper surface using laser ablation and water emulsion of surfactants

Wettability is one of the main characteristics of a surface and reflects the ability of a liquid to flow over a solid surface. Using hydrophobic functional surfaces in evaporator and condenser of heating plants to intensify heat exchange processes will increase efficiency and, consequently, reduce the metal consumption and weight-size parameters of this equipment. This will result in reduced energy consumption and lower production and operating costs. This paper presents an analysis of methods for creating hydrophobic surfaces. The fabrication of hydrophobic copper surface of experimental samples by creating multimodal relief in form of 50 µm grid by laser ablation process and subsequent reduction of surface energy of material using water emulsion of octadecylamine is grounded and described. The fluence was varied from 5 to 900 J/cm2 when modifying the surface using laser station. The dependence of the effect of laser fluence on water contact angle value is presented. Following the study, the optimum laser irradiation parameters for the surface of experimental samples were determined, at which the maximum value of water contact angle of 146.61° and the minimum value of roll-off angle of 13.5° were obtained.

Physical simulation of thermomechanics of gas flows in the output channels of turbocharger centrifugal compressor

It is known that the thermal and mechanical characteristics of the air flow in the output channel of the turbocharger compressor largely determine the efficiency and quality of the gas exchange processes of the piston engine. The research was carried out on an experimental installation containing a turbocharger, output channels of different configurations, a measurement database and a data collection system. It was found that the stabilization of the flow in the output channel of the compressor leads to a significant increase in the heat transfer intensity (up to 25 %) compared to the base pipeline, while reducing the degree of turbulence by up to 30 %. In the output channel of the compressor with grooves, there is an even more significant increase in the heat transfer intensity (up to 30 %) with an increase in the degree of turbulence by up to 12% compared to the base channel. The proposed configurations of the compressor output channels can be used to intensify heat exchange in order to naturally cool the air during the intake process, as well as to stabilize the gas dynamic parameters of the flow in order to reduce the hydraulic resistance of the intake system of the turbocharged engine.