脉动流场对波壁管内流体的传热及阻力的影响

The Influence of Pulsating Flow Field on the Heat Transfer and Resistance of the Fluid in the Wave-Wall Tube

为了解决换热器、发动机等设备热质传递效率低的问题,采用数值模拟和实验相结合的方法,入口速度设为具有正弦脉动特点的非定常边界、流体温度设为348 K;出口速度设为自由出口、壁面温度设为298 K、忽略管壁传热热阻;对Re=600时波壁管内流体的传热和阻力特性进行研究,分析了不同时刻管内流体的速度场和温度场,以及努塞尔数Nu和摩擦系数的变化规律,将定常和脉动流场下流体的传热及流动特性进行了对比。结果表明:脉动流场下波壁管内流体的换热效果较定常流场差异明显,在振动分率P=1.5,斯德鲁哈尔数St=2.8时,脉动流场较定常流场的Nu增幅达34%,而在P=0.5,Re=400时,脉动流场较定常流场的Nu增幅达55%;脉动流动下,摩擦系数呈现正弦规律;在瞬时雷诺数Re时,脉动流场下的平均摩擦系数与定常流场相比差别不大,但瞬时摩擦系数差异显著。

In order to solve the problem of low heat and mass transfer efficiency of equipment such as heat exchange and engine,the method of combining numerical simulation and experiment was adopted.The inlet velocity was set as the unsteady boundary with sinusoidal pulsation,and the fluid temperature was set as 348 K.The outlet velocity was set as the free outlet,the wall temperature was set as 298 K,and wall heat transfer resistance was ignored.The heat transfer and resistance characteristics of the fluid in the wavewall tube at Re=600 were studied,and the velocity and temperature fields of the fluid in the tube at different moments,as well as the changing rules of the nussel number Nu and the friction coefficient were analyzed.The heat transfer and flow characteristics of the fluid in the steady and pulsating flow fields were compared.The results showed that the heat transfer effect of the fluid in the wave wall tube was significantly different from that in the steady flow field under the pulsating flow field.With the vibration fraction P=1.5 and the number St=2.8,the Nu of pulsed flow field was increased by 34%,while with P=0.5 and Re=400,the Nu of pulsed flow field was increased by 55%compared to that with the steady flow field.Under pulsating flow,it was found that the friction coefficient was sinusoidal under pulsating flow.When the instantaneous Reynolds number is Re,the average friction coefficient of pulsating flow field had little difference with that of steady flow field,but the instantaneous friction coefficient had significant difference.