ACTA AERONAUTICAET ASTRONAUTICA SINICA >
Flow direction effect on heat transfer of supercritical CO2 in helically coiled tube
Received date: 2015-06-19
Revised date: 2015-09-02
Online published: 2015-09-16
Supported by
National Natural Science Foundation of China (51206197); the Fundamental Research Funds for the Central Universities (CDJZR12140032); Project supportod by Graduate Scientific Research and Innoration of Chongqing (CYS16011)
Numerical analysis on heat transfer of supercritical CO2 in heated vertical helically coiled tubes is performed by renormalization group (RNG) k-ε turbulent model. The tube diameter, effective heated length, tube pitch, curvature diameter are 9 mm, 5.5 m, 32 mm and 283 mm, respectively. The influences of the mass flux, inlet pressure, heat flux and flow direction on heat transfer and pressure drop of supercritical CO2 are studied. Furthermore, the combined effects of variable physical properties, buoyancy and centrifugal force in different flow directions of helically coiled tubes on heat transfer are analyzed. It is found that the influence of the buoyancy on the supercritical fluid flow up and down in helically coiled tubes is not significant, while the influence of the buoyancy in the horizontal direction is great, especially when the ratio of the distance which a cross-section of helically coiled tube to the entrance section and the pipe diameteris between 150 and 350 (near the critical temperature). The variable physical properties, the coupling effect of buoyancy and centrifugal force cause the fluctuation of the horizontal heat transfer coefficient.
LI Hongrui , XU Xiaoxiao , LIU Chao , LIU Xinxin . Flow direction effect on heat transfer of supercritical CO2 in helically coiled tube[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2016 , 37(7) : 2123 -2131 . DOI: 10.7527/S1000-6893.2015.0245
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