竖直圆管中超临界压力CO2在低Re数下对流换热研究  

CONVECTION HEAT TRANSFER OF CO_2 AT SUPERCRITICAL PRESSURES IN A VERTICAL TUBE AT LOW REYNOLDS NUMBERS

作　　者：张宇[1] 姜培学[1] 石润富[1] 邓建强[1] 

机构地区：[1]热科学与动力工程教育部重点实验室,清华大学热能工程系,北京100084

出　　处：《工程热物理学报》2008年第1期118-120,共3页Journal of Engineering Thermophysics

基　　金：国家杰出青年自然科学基金(No．50025617)

摘　　要：本文对超临界压力CO_2自下而上流过内径为2mm的加热圆管,在低进口Re(Re_(in)≈1700)条件下的对流换热进行了数值模拟,并与实验结果进行了比较。结果表明,在进口雷诺数较低(Re_(in)≈1700)而热流密度较高时,由于密度变化导致浮升力对流动产生扰动,流动从层流提前转变为湍流,换热大大增强并导致壁面温度的异常分布。使用LB湍流模型可以较好地模拟此时流动从层流向湍流的过渡现象,而采用层流与湍流相结合的分区计算方法的结果与实验测量值吻合得更好。由于浮升力的影响,径向速度呈M型分布,速度最大值在靠近壁面某处;当热流密度很大时,在管子中心区会出现回流。Convection heat transfer of supercritical pressure CO2 flowing upward in a vertical 2 mm diameter heated tube at low Reynolds numbers （1700） was investigated numerically. The numerical results were compared with experimental data. The results showed that convection heat transfer was enhanced for the cases with low inlet Reynolds numbers （Rein ≈ 1700） and high heat fluxes due to the strong influence of buoyancy which results in an early transition from laminar to turbulent flow. The numerical simulation using the LB turbulence model can properly simulate the transition from laminar to turbulent flow. However, the numerical results with the combination of the laminar model and the turbulence model corresponded very well with the experimental data. The M shape distribution of radial velocity appeared in the tube due to strong buoyancy. For high heat fluxes, the fluid flow around the middle tube exist reversed flow.

关 键 词：超临界压力 对流换热 浮升力 层流 湍流 

分 类 号：TK124[动力工程及工程热物理—工程热物理]