Convection heat transfer of supercritical pressure carbon dioxide in a vertical micro tube from transition to turbulent flow regime
Convection heat transfer of supercritical pressure carbon dioxide in a vertical micro tube from transition to turbulent flow regime
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DOI：
10.1016/j.ijheatmasstransfer.2012.08.038
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发表时间：
2013
影响因子：
5.2
通讯作者：
P. Jiang;Bo Liu;Chenru Zhao;Feng Luo
中科院分区：
文献类型：
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作者：
P. Jiang;Bo Liu;Chenru Zhao;Feng Luo
本文对内径为99.2 μm的垂直管内超临界压力下CO2的对流换热进行了实验研究。由于加热和压力降的浮力和流动加速的影响进行了评估和分析。结果表明，在临界点附近的压力和较低的进口雷诺数下，当热流密度较高时，流动加速效应显著，壁面局部温度随压力的变化呈非线性变化。在入口雷诺数为2600 ~ 6700、热流密度为85 ~ 748 kW/m2的条件下，微尺度管内的浮力对换热的影响可以忽略不计。在高热流密度和低进口雷诺数条件下，由于加热和压降引起的流动加速会强烈影响湍流度，并降低传热。数值计算结果与实验数据的比较表明，AKN低雷诺数湍流模型比采用增强壁面处理的k-ε可实现湍流模型的计算结果更接近实验数据。
This paper presents experimental investigations of the convection heat transfer of carbon dioxide at supercritical pressures in a vertical tube with inner diameter of 99.2 μm for various Reynolds numbers, heat fluxes and flow directions. The effects of buoyancy and flow acceleration due to heating and pressure drop are evaluated and analysed. The results show that the effects of flow acceleration are significant and the local wall temperature varies non-linearly for both upward and downward flows at the pressures in the vicinity of critical point and low inlet Reynolds numbers when the heat fluxes are relatively high. The buoyancy effect on the heat transfer is negligible in micron scale tubes at inlet Reynolds (from 2600 to 6700) and various heat fluxes (from 85 kW/m2to 748 kW/m2). The flow acceleration due to heating and pressure drop can strongly influence the turbulence and reduce the heat transfer for high heat fluxes and low inlet Reynolds. Comparison of numerical predictions with the experimental data showed that the AKN low Reynolds number turbulence model gave better agreement than thek–εrealizable turbulence model with the enhanced wall treatment.