FRICTION FACTOR EQUATIONS ACCURACY FOR SINGLE AND TWO-PHASE FLOWS

Estimate pressure drop throughout petroleum production and transport system has an important role to properly sizing the various parameters involved in those complex facilities. One of the most challenging variables used to calculate the pressure drop is the friction factor, also known as Darcy-Weisbach's friction factor. In this context, Colebrook's equation is recognized by many engineers and scientists as the most accurate equation to estimate it. However, due to its computational cost, since it is an implicit equation, several explicit equations have been developed over the decades to accurately estimate friction factor in a straightforward way. This paper aims to investigate accuracy of 46 of those explicit equations and Colebrook implicit equation against 2397 experimental points from single-phase and two-phase flows, with Reynolds number between 3000 and 735000 and relative roughness between 0 and 1.40x10-3. Applying three different statistical metrics, we concluded that the best explicit equation, proposed by Achour et al. ( 2002), presented better accuracy to estimate friction factor than Colebrook's equation. On the other hand, we also showed that equations developed by Wood (1966), Rao and Kumar (2007) and Brkic (2016) must be used in specifics conditions which were developed, otherwise can produce highly inaccurate results. The remaining equations presented good accuracy and can be applied, however, presented similar or lower accuracy than Colebrook's equation.