Studies on frictional pressure drop of gas-non-Newtonian fluid two-phase flow in the vacuum sewers

Abstract

Calculating pressure drop of gas–liquid two-phase flow in sewage pipes is of great importance for designing and choosing safely and economically a vacuum sewers pipe network system, including power equipment and vacuum pipes, for transporting non-Newtonian fluid such as black water (mixture of dejecta and water) and sewage sludge, and so on. The aim of this article is to predict the characteristics of the multi-phase flow frictional pressure loss in the sewage pipes. First, a study has been undertaken to investigate two-phase flow frictional pressure loss with a mixture of air and black water non-Newtonian liquids in sewers pipes and the effects of gas and liquid flowrate on two-phase frictional pressure drop. A general correlation for calculating frictional pressure gradient during gas-non-Newtonian two-phase flow in pipes has been deduced, and the validity of the method applied to calculate pressure drop of gas-non-Newtonian two-phase flow has been compared and discussed with respect to several experiments on black water and air two-phase flow in a horizontal pipe. The calculated results are in agreement with the experimental results on the whole.

Keywords:

• Vacuum sewer
• Sewage pipe
• Non-Newtonian fluid
• Gas–liquid two-phase flow
• Frictional pressure gradient