板式换热器内钻井液流动与传热特性数值模拟研究

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

摘要:

深部油气与地热钻探中，井底高温导致钻井液性能劣化，严重威胁作业安全与效率。板式换热器作为钻井液冷却系统的核心装备，其内部流动与传热特性是决定系统性能的关键。本文以耐高温水基钻井液为对象，采用ANSYS Fluent开展共轭传热数值模拟，结合室内冷却试验完成模型验证，系统研究了宽雷诺数范围内（17≤Re_m<1700）流场离散性、压降、努塞尔数、热阻分布及综合性能指标的演变规律。结果表明：钻井液流经板片触点后会诱发流动分离形成低速涡流区，该区域是污垢沉积的高风险区；流场离散性与压降随Re_m的变化呈分段非线性演变，清晰标识了流动从层流向湍流的转变过程，Re_m=50为层流?过渡流临界点；随Re_m增加，Nu显著提高但其增长率呈四阶段下降，系统主导热阻在Re_m<560时受钻井液侧控制，Re_m>560后转为水侧限制；综合性能指标随Re_m增加持续下降，表明单纯提高钻井液流速带来的换热增益增速低于流动阻力增幅，综合能效持续衰减。研究揭示了高黏钻井液传热强化与流动阻力之间的权衡机制，为高温钻井液冷却系统的优化设计与运行调控提供了理论支撑。

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.