A new friction factor formula for single phase liquid flow through geothermal pipelines

Abstract

Proper selection of pumps has been an important issue for energy efficiency in geothermal energy. In a research conducted among machines that consume electricity, pumps come first with 25 %. Accurate estimation of pressure losses is a key point in order to select pump systems. Hot water from the geothermal area is carried by pipeline systems. In this study, extensive experimental study is conducted at Izmir Katip Celebi University Flow Loop using pure water for fluid temperature from 25 °C to 60 °C, for four various relative roughness values, and for Reynolds Number ranges from 6.2 × 104 to 7.8 × 105. This study has mainly two objectives: First is to identify if the absolute pipe roughness values of commercially available pipes vary according to the pipe diameter. The second objective is to investigate fluid temperature effects on frictional pressure losses in rough pipes and to present a new friction factor correlation for using in geothermal pipelines, considering the fluid temperature effects. Experimental study shows that absolute pipe roughness varies substantially for pipe diameters. The proposed friction factor has a good agreement with explicit formulas of Blasius (1913) and Taler (2016) equations for smooth pipes and Colebrook (1939) equation for rough pipes, as well as experimental data at various temperature values.Additionally, frictional pressure losses are accurately estimated using new friction factor equation. Results show that both relative roughness and temperature have a significant influence on the friction factor for turbulent flow through rough pipes. For this reason, pipe roughness should be determined correctly and the effects of fluid temperature on pressure losses should be considered. This may influence frictional head losses per unit length and, consequently, the predicted pumping requirements in geothermal pipelines.