Discrepancy in Predicted Head Loss of Non-Newtonian Aqueous Suspension of Fly Ash with Two Different Yield Stress Values Obtained from Rheological Data

Abstract

The rheological behavior of aqueous suspension of fly ash in 60–70% concentration range by weight has been investigated using a high precision rotational rheometer. The nature of the slurry indicated non-Newtonian Bingham plastic. Using Darby et al.’s correlation, the combined laminar and turbulent fanning friction factors for the suspension were evaluated with the help of Bingham parameters such as yield stress (τ0) and Bingham viscosity (ηp), and the head loss of fly ash suspension was predicted at weight concentrations of 60, 65, 68, 69 and 70% in a 400 NB mild steel pipe. Besides, the yield stress (τ0sg) of the ash suspension samples was determined by using stress–growth method in the concentration range of 60–75% by weight. The τ0sg values so obtained were then again used to evaluate the head loss of the suspension with the same value of Bingham viscosity at the specified concentrations. It was observed that the head loss predicted by using τ0sg values from stress–growth method incurred lower frictional losses as compared to head losses by using the τ0 values obtained from linear fit of shear stress–shear rate data. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.