LNG绕管式换热器管内压降和传热的数值模拟

Numerical Simulation of Pressure Drop and Heat Transfer inside Tube of LNG Coil-Wound Heat Exchanger

针对目前LNG绕管式换热器在设计时存在管内低温传热的不确定性,采用FLUENT软件分析了大螺距螺旋管在湍流状态下管内的压降和冷却传热特征。研究中分别采用4.8 MPa的气态甲烷和液态甲烷为介质,探讨了螺旋管结构、雷诺数Re、普朗特数Pr对压降和努塞尔数Nu的影响。结果表明:管径、缠绕直径、Re及Pr对压降和Nu的影响较大;螺距对传热和压降影响较小,可忽略不计。并将模拟值与Jayakumar等半经验值做对比,结果趋势一致。最后拟合出适用于LNG低温冷却状态下的Nu公式,为LNG绕管式换热器的工艺计算提供一定的依据。

In the view of the uncertainty of the low temperature heat transfer in the tube for the design of LNG coil-wound heat exchanger,the pressure drop and heat transfer characteristics inside tube of large pitch’s spiral under turbulent flow were analyzed by FLUENT software. Gaseous methane and liquid methane of 4. 8 MPa were used as the medium,and the effects of spiral tube’s structure,Re and Pr on the pressure drop and Nu were analyzed. The results show that the effects of tube diameter,winding diameter,Re and Pr on the pressure drop and Nu are relatively larger,and the effect of pitch on the pressure drop and Nu is smaller which can be negligible. The simulation results were compared with the results of Jayakumar etc.,and the trend had no difference. The Nu formula suitable for LNG under cryogenic cooling condition was proposed,and it provided the accordance with the technology calculaton of the LNG coil-wound heat exchanger.