Effect of surfactants on surface criteria in laminar boundary layer
It is shown that on the border the flow of the coolant − wall pipe, that is, within the laminar boundary layer (LBL), there is a powerful field of forces of surface tension. The intensity of surface forces characterized by superficial criteria The value surface of the criterion Reynolds and Euler's criterion in LBL several orders of magnitude more from the Froude criterion and inverse of the Reynolds criterion, so the latter can be neglected. Experimentally found value of surface tension, cosine of the contact angle and dynamic viscosity of aqueous solutions influenced by surfactants. To aqueous solutions were added the most common anionic, nonionic and cationic surfactants. The optimal concentrations of anionic, nonionic and cationic surfactants in the «icy» water. It is established that at the optimal concentration of surfactant surface tension value is minimum. For these concentration surfactant were chosen and the value for dynamic coefficient of viscosity. We calculated average thickness of the laminar boundary layer when added to water, the optimal concentration of the studied surfactants. It is established that the reduction of surface tension minimizes the thickness of laminar boundary layers in the wall of the pipe–water. It is shown that the average speed in the near-wall layers for adding optimum concentrations of the studied surfactants. increases, and as a result this system is able to effectively transfer heat. Defined numerical ranges of the surface criterion for «ice» water with the addition of various surfactants. It is established that the value surface of the criterion of Ро depend on the surface tension of the coolant. It was experimentally confirmed that when optimal concentrations of surfactant, there is a minimum value surface of the criterion of Ро. From the graph based on superficial criteria from concentrations of surfactant, it is possible to determine the surface criterion and speed in LBL.
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