The characteristics and mechanisms of self-excited oscillation pulsating flow on heat transfer deterioration of supercritical CO2 heated in vertical upward tube
The characteristics and mechanisms of self-excited oscillation pulsating flow on heat transfer deterioration of supercritical CO2 heated in vertical upward tube
复制标题
自激振荡脉动流对垂直向上管加热超临界CO2传热恶化的特性及机理
DOI：
10.1016/j.applthermaleng.2021.117839
复制
发表时间：
2021-11
期刊：
影响因子：
--
通讯作者：
Chaobin Dang
中科院分区：
文献类型：
--
作者：
Dan Li;Xiaoxiao Xu;Yong Cao;Chao Liu;Shijie Zhang;Chaobin Dang
超临界CO_2在管内受热时，由于局部高温的出现，其换热劣化会影响系统的效率和安全运行。为了抑制和延缓超临界CO2的HTD，通过实验和模拟研究了超临界CO2 HTD的自激振荡脉动流动的特性和机理。在竖管入口引入亥姆霍兹振荡器，以产生脉动的超临界二氧化碳气流。并与管口无亥姆霍兹振子的换热性能进行了比较。结果表明，自激振荡脉动流动显著改善了换热性能。在伪临界点(TPC)之前，换热参数沿流动方向呈现小幅度振荡。平均换热系数最大可达3.4倍，强化主要发生在受热管入口段的HTD区域。热流密度越高，抑制HTD的效果越明显，当热流密度为200kW/m2时，壁温峰值可降低100kW。与定常流动相比，基于速度、湍动能和密度径向分布的自激振荡脉动流的机理分析表明，“M-−”型速度分布出现的时间较晚，且较为平缓。TKE的生产和扩散在对数层(30r；y+t；t；0.2r)得到改善。此外，周期和幅值在换热性能上不呈现单调变化趋势。对脉动参数对换热系数的影响进行了优化，在计算的算例中，S周期为0.016，脉动幅度为100亿kg/m2·S的换热性能最好。
Heat transfer deterioration (HTD) of supercritical CO2heated in a tube influences the efficiency and safe operation of the system due to the occurrence of local high temperature. To suppress and delay the HTD, the characteristics and mechanisms of self-excited oscillation pulsating flow on HTD of supercritical CO2are studied by experiment and simulation at pressure 8 MPa, mass fluxes from 350 to 800 kg/m2·s, heat fluxes from 30 to 200 kW/m2. The Helmholtz oscillator is introduced into the inlet of the vertical tube for generating a pulsating flow of supercritical CO2. The heat transfer performance is compared with that of without Helmholtz oscillator at the inlet of the tube. The results show that the self-excited oscillation pulsating flow improve the heat transfer performance significantly. The heat transfer parameters present oscillations with small amplitude along flow direction before pseudo-critical point (Tpc). The average heat transfer coefficient can be up to 3.4 times and the enhancement takes place mainly at the HTD region which is located at the entrance section of the heated tube. The effect of suppressing HTD is more significant at higher heat flux, and the peak of wall temperature can be reduced by 100 K at a heat flux of 200 kW/m2. Compared to the steady flow, the mechanism analysis of the self-excited oscillation pulsating flow based on radial distributions of velocity, turbulent kinetic energy (TKE), and density reveals that the velocity distribution of “M−shape” appears later and gentler. The production and diffusion of TKE are improved at log layer (30 <y+< 0.2r). In addition, the period and the amplitude do not show monotonous trends on heat transfer performance. The effects of pulsating parameters on HTD are optimized that the heat transfer performance with the period of 0.016 s and the amplitude of 100 kg/m2·s is the best in calculated cases.
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DOI：
10.1016/j.ijheatmasstransfer.2015.05.109
发表时间：
2015-10
影响因子：
5.2
作者：
Qing Zhang;Huixiong Li;Weiqiang Zhang;Liangxing Li;X. Lei
通讯作者：
Qing Zhang;Huixiong Li;Weiqiang Zhang;Liangxing Li;X. Lei
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影响因子：
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作者：
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通讯作者：
Cai Can
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DOI：
10.1016/j.ijheatmasstransfer.2015.02.013
发表时间：
2015-06
影响因子：
5.2
作者：
Zhan-Bin Liu;Ya-Ling He;Zhi-Guo Qu;Wen-Quan Tao
通讯作者：
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影响因子：
11.2
作者：
Shijie Zhang;Xiaoxiao Xu;Chao Liu;Chaobin Dang
通讯作者：
Chaobin Dang
影响因子：
4.5
作者：
Feng Sun;Yong Li;B. Sundén;G. Xie
通讯作者：
Feng Sun;Yong Li;B. Sundén;G. Xie