Experimental investigation of friction coefficient in water vapor transportation pipelines under sub-atmospheric pressure

Abstract

This study provides a comprehensive analysis of the friction coefficient between pipe walls and water vapor under sub-atmospheric pressure conditions, highlighting its implications for the design and operational efficiency of fluid systems. Through a series of rigorous experiments, the research examines the interplay of varying temperatures, pressures, and flow rates on the performance of transmission pipes of different diameters. The findings indicate that the friction coefficient increases as pressure decreases. Notably, the ratio of the friction coefficient between vacuum and atmospheric conditions can increase significantly based on pressure, reaching values of up to 27 in laminar flow and 18 in turbulent flow. An increase in pipe diameter and flow rate under vacuum conditions correlates with a rise in the friction coefficient. It was also observed that under complete vacuum conditions, both laminar and turbulent flow have no impact on the friction coefficient, and unlike atmospheric conditions, they do not influence the graph of the friction coefficient across different Reynolds numbers. The Kooshi-Attar equation, a novel formulation derived with the assistance of artificial intelligence, has been introduced to estimate the friction coefficient at sub-atmospheric pressures. This equation demonstrates a prediction accuracy exceeding 93 %, providing a valuable analytical tool for optimizing fluid system designs.