Method for calculating the coefficient of hydraulic resistance of a coaxial heat exchanger with rough walls

• Published in: International journal of heat and mass transfer 2022-08, Vol.192, p.122917, Article 122917
• Main Authors: Pisarevsky, M.I., Korsun, A.S., Struchalin, P.G., Fedoseev, V.N.
• Format: Article
• Language: English
• Subjects: Artificial roughness; Coaxial heat exchanger; Coefficients; Experimental data; Heat exchangers; Hydraulic resistance; Hydraulics; Mathematical analysis; Roughness; Shear stress; Stresses; Turbulent flow; Velocity distribution
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2022.122917

•Turbulent motion of the fluid in the annular channels was studied.•New method allows us to calculate the hydraulic resistance coefficient of an annular channel with a rough wall.•Line of zero tangential stresses is shifted due to the difference in the surface states of channel walls.•The second constant of the universal velocity profile changes due to the presence of roughness on the channel wall.•Experimental data of 11 working sites have been published. [Display omitted] A method for calculating the coefficient of hydraulic resistance of a coaxial heat exchanger with different roughness of opposite walls is proposed. According to the technique, the annular section of the heat exchanger channel is divided by a line of zero shear stress into two non-interacting annular layers. The balance equations in the layers and the channel together with the condition of matching the velocities of the layers on the zero shear stresses line form a closed system of equations. The solution of the system allows calculating the coefficient of hydraulic resistance of the channel as a whole, the position of the line of zero shear stresses, average velocities in each of the layers, the value of the second constant of the universal velocity profile. The method was verified in several ways, which showed the maximum deviation of the calculated values from the data of other authors and the results of our experiments, no more than 7%. In our experiments, we used three two-dimensional artificial roughness profiles: rectangular, trapezoidal, and triangular.