Empirical Formulas for Calculation of Negative Pressure Difference in Vacuum Pipelines

The paper presents the analysis of results of empirical investigations of a negative pressure difference in vacuum pipelines with internal diameters of 57, 81, 102 mm. The investigations were performed in an experimental installation of a vacuum sewage system, built in a laboratory hall on a scale of 1:1. The paper contains a review of the literature concerning two-phase flows (liquid-gas) in horizontal, vertical and diagonal pipelines. It presents the construction and working principles of the experimental installation of vacuum sewage system in steady and unsteady conditions during a two-phase flow of water and air. It also presents a methodology for determination of formula for calculation of a negative pressure difference in vacuum pipelines. The results obtained from the measurements of the negative pressure difference Δp_vr in the vacuum pipelines were analyzed and compared with the results of calculations of the negative pressure difference Δp_vr, obtained from the determined formula. The values of the negative pressure difference Δp_vr calculated for the vacuum pipelines with internal diameters of 57, 81, and 102 mm with the use of Formula (19) coincide with the values of Δp_vr measured in the experimental installation of a vacuum sewage system. The dependence of the negative pressure difference Δp_vr along the length of the vacuum pipelines on the set negative pressure in the vacuum container p_vzp is linear. The smaller the vacuum pipeline diameter, the greater the negative pressure difference Δp_vr is along its length.