Verification of models for calculating the hydraulic friction coefficient in water heat networks

Statement of the problem. The active development of turbulence theory occurred in the twentieth century and many authors proposed their models that allow determining the coefficient of hydraulic friction for various categories of pipelines depending on the fluid flow mode. A comprehensive analysis of the adequacy of using various models to find the coefficient of hydraulic friction for the design conditions of heating networks has not been carried out, and it is not completely clear what errors occur when using them. Results. The results of calculating the coefficient of hydraulic friction are presented using currently used models in the range of water flow rates in heating networks from 0,1 to 3,5 m/s, for new steel pipelines with an internal diameter from 26 to 1396 mm. Equations are proposed that allow calculating the values of the relative error in calculating the coefficient of hydraulic friction using various models. Based on the Altshul equation, an expression is proposed that allows for a high-accuracy approximation of the Colebrook — White model. Conclusions. The applied models for calculating the coefficient of hydraulic friction give the closest results in the area of the quadratic law of resistance with an internal diameter of 412 mm, with a decrease in diameters the average value of the relative error increases, reaching 16,8 %. The proposed equations allow in practice to carry out calculations with high accuracy without implementing numerical methods.