The characteristics and mechanisms of self-excited oscillation pulsating flow on heat transfer deterioration of supercritical CO2 heated in vertical upward tube

2021 ◽  
pp. 117839
Author(s):  
Dan Li ◽  
Xiaoxiao Xu ◽  
Yong Cao ◽  
Chao Liu ◽  
Shijie Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Supercritical Co2 ◽  
Pulsating Flow ◽  
Heat Transfer Deterioration ◽  
Excited Oscillation

Numerical study on the heat transfer deterioration and its mitigations for supercritical CO2 flowing in a horizontal miniature tube

2021 ◽  
Vol 151 ◽  
pp. 107982
Author(s):  
Chika Eze ◽  
Shahid Ali Khan ◽  
Kwun Ting Lau ◽  
Shakeel Ahmad ◽  
Lin Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Supercritical Co2 ◽  
Numerical Study ◽  
Heat Transfer Deterioration

Mitigation of heat transfer deterioration in a circular tube with supercritical CO2 using a novel small-scale multiple vortex generator

2020 ◽  
Vol 156 ◽  
pp. 106481
Author(s):  
Chika Eze ◽  
Kwun Ting Lau ◽  
Shakeel Ahmad ◽  
Nnaemeka Nnamani ◽  
Thomas Ferrand ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Supercritical Co2 ◽  
Circular Tube ◽  
Vortex Generator ◽  
Small Scale ◽  
Heat Transfer Deterioration

Numerical Investigation on Conjugate Heat Transfer of Supercritical CO2 in a Horizontal Double-Pipe Heat Exchanger

2017 ◽  
Author(s):  
Zhenxing Zhao ◽  
Jun Wu ◽  
Yuansheng Lin ◽  
Qi Xiao ◽  
Fan Bai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Supercritical Fluid ◽  
Supercritical Co2 ◽  
Conjugate Heat Transfer ◽  
High Mass ◽  
Heat Transfer Deterioration ◽  
Flow And Heat Transfer ◽  
Double Pipe ◽  
Pipe Heat

The special fluid flow and heat transfer characteristics of supercritical CO2 in a horizontal double-pipe heat exchanger have been numerically investigated. The AKN k-epsilon model was selected to model the turbulent flow and heat transfer of supercritical fluid. In conjugate heat transfer process, there exists obvious heat transfer deterioration on the top wall for horizontal flow. The region of heat transfer deterioration expands with the increased GShell or TShell,0, and the influence of TShell,0 on conjugate heat transfer is greater than that of GShell. The high-temperature fluid will gather near the top region. The intensity and position of the secondary flow can represent the turbulence heat transfer. When the supercritical fluid temperature is much higher than Tpc, buoyancy force can be omitted, but it can not been neglected even under relatively high mass flux.

scholarly journals Numerical Analysis on Heat Transfer Characteristics of Supercritical CO2 in Heated Vertical Up-Flow Tube

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 723
Author(s):  
Chenshuai Yan ◽  
Jinliang Xu ◽  
Bingguo Zhu ◽  
Guanglin Liu
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Wall Temperature ◽  
Supercritical Co2 ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Safe Operation ◽  
Flow Tube ◽  
Heat Transfer Deterioration ◽  
Vertical Up

It is great significance to understand the mechanism of heat transfer deterioration of supercritical CO2 for heat exchanger design and safe operation in the supercritical CO2 Brayton cycle. Three-dimensional steady-state numerical simulation was performed to investigate the behavior of supercritical CO2 heat transfer in heated vertical up-flow tube with inner diameter di = 10 mm and heated length Lh = 2000 mm. Based on the characteristics of inverted-annular film boiling at subcritical pressure, the heat transfer model of supercritical CO2 flowing in the heated vertical tube was established in this paper. The mechanisms of heat transfer deterioration (HTD) and heat transfer recovery (HTR) for supercritical CO2 were discussed. Numerical results demonstrate that HTD is affected by multiple factors, such as the thickness and property of vapor-like film near the wall, the turbulence intensity near the interface between liquid-like and vapor-like, and in the liquid-like core region as well as the distribution of radial velocity vector. Among the above factors, the change of turbulent kinetic energy caused by the buoyancy effect seems to be a more important contributor to HTD and HTR. Furthermore, the influences of heat flux and mass flux on the distribution of wall temperature were analyzed, respectively. The reasons for the difference in wall temperature at different heat fluxes and mass fluxes were explained by capturing detailed thermal physical properties and turbulence fields. The present investigation can provide valuable information for the design optimization and safe operation of a supercritical CO2 heat exchanger.

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