CuO-H_2O纳米流体强化换热的数值模拟

Numerical Simulation of the Intensified Heat Exchange of CUO-H_2O Nano-fluid

采用数值模拟的方法研究了矩形腔内Cu O-H2O纳米流体自然对流的换热特性和换热机理。重点分析了二维封闭腔内不同Ra数下,纳米颗粒体积分数和粒径对Cu OH2O纳米流体自然对流时温度场和速度场的影响,并探讨了纳米颗粒布朗运动对换热的影响。数值模拟结果表明:对于给定的Ra数,随着体积分数的增大和颗粒粒径的减小,纳米流体的换热效果会显著增强;当Ra数较小时,换热形式主要表现为热传导,随着Ra数的增大,换热形式逐渐变为以热对流为主;纳米颗粒布朗运动是影响纳米流体换热的重要因素,随着布朗运动的增强,纳米流体内部的能量传递增强,从而使换热增强。

By using the numerical simulation method,studied were the natural convection-based heat exchange characteristics and of CUO-H2 O nano-fluid inside a rectangular cavity and the mechanism governing the heat exchange. The emphasis was placed on an analysis of the influence of volumetric fraction and particle size of the nano-fluid on the temperature and speed field inside a two-dimensional enclosed cavity at various Ra numbers formed when the CUOH2 O nano-fluid is undergoing the natural convection and an investigation of the influence of Brownian movement of nano-fluid on the heat exchange. The numerical simulation results show that for a given Ra number,the heat exchange efficiency of the nano-fluid will notably enhance. When Ra number is relatively small,the heat exchange is mainly regarded as the heat conduction. With an increase of Ra number,the heat exchange will gradually become a convection-based heat exchange. Brownian movement of the nano-particles will become an important factor influen-cing the heat exchange of the nano-fluid. With the enhancement of Brownian movement,the energy transfer inside the nano-fluid will also enhance,thus intensifying the heat exchange.