摘要:
采用RNG k-ε湍流模型对超临界CO2流体在内径为4 mm,长度2000 mm,节距为10 mm,曲率为0.1的水平螺旋管内的冷却换热进行了数值模拟.研究了质量流量、热流量以及压力对换热系数的影响,并和超临界CO2在水平直管内的冷却换热进行了对比.研究结果表明,超临界CO2在水平螺旋管内流动产生的二次流强于水平直管内的二次流,前者的换热系数大于后者；换热系数随质量流量的增加而增大；在似气体区,换热系数随着热流量的增加而增大,而在似液体区,热流量对换热系数几乎没有影响；换热系数峰值点随着压力的升高而下降,并向高温区偏移.
Abstract:
In the present study, cooling heat transfer of supercritical CO2 in a horizontal helically coiled-tube 4 mm in diameter, 2000 mm in length, a pitch of 10 mm and 0.1 in curvature is numerically investigated with RNG turbulence model. Influences of mass flow rate, heat flux and pressure on heat transfer of supercritical CO2 are studied. The characteristics of the flow and heat transfer are compared with those in a horizontal straight tube. Results show that the secondary flow and heat transfer coe?cient in a helically coiled tube is obviously larger than in a horizontal straight tube. The heat transfer coe?cient of supercritical CO2 increases with increasing mass flow rate, and the heat transfer coe?cient increases slightly as the heat flux increases in the gas-like region, while the heat transfer coe?cient is unaffected by heat flux in the liquid-like region. The peak of the heat transfer coe?cient decreases and shifts to a higher temperature region as the pressure increases.
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