Numerical simulation of flow and heat transfer characteristics of drilling fluid in a plate heat exchanger

Abstract:

In deep oil， gas， and geothermal drilling， elevated bottom-hole temperatures degrade drilling fluid performance， posing a severe threat to operational safety and efficiency. As the core equipment of the drilling fluid cooling system， the plate heat exchanger （PHE） has internal flow and heat transfer characteristics that critically determine overall system performance. In this study， a high-temperature-resistant water-based drilling fluid was investigated via conjugate heat transfer numerical simulations using ANSYS Fluent， with model validation performed with laboratory cooling experiments. The evolution of flow field non-uniformity， pressure drop， Nusselt number （Nu）， thermal resistance distribution， and comprehensive performance index was systematically analyzed over a wide Reynolds number range （17≤Re_m<1700）. The results demonstrate that flow separation induced as the drilling fluid flows past plate contact points generates low-velocity vortex zones， which are identified as high-risk regions for fouling deposition. Both flow field non-uniformity and pressure drop exhibit piecewise nonlinear variations with increasing Re_m， clearly delineating the transition from laminar to turbulent flow， with Re_m=50 identified as the laminar-to-transitional critical threshold. As Re_m increases， Nu increases substantially， yet its growth rate declines through four distinct stages. The dominant thermal resistance shifts from the drilling fluid side to the water side when Re_m>560. The comprehensive performance index decreases continuously with increasing Re_m， indicating that the heat transfer gain per unit increase in flow velocity grows more slowly than the accompanying rise in flow resistance， leading to sustained degradation in overall energy efficiency. This study elucidates the trade-off mechanism between heat transfer enhancement and flow resistance for high-viscosity drilling fluids， providing theoretical support for the optimal design and operational regulation of high-temperature drilling fluid cooling systems.