Numerical Study on Heat Transfer Deterioration of Supercritical n-Decane in Horizontal Circular Tubes

Energies

Yanhong Wang²  Sufen Li¹  Ming Dong² 

[1] School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China;

关键词: supercritical pressure;    n-decane;    convective heat transfer;    heat transfer deterioration;    critical condition;    numerical study;   

DOI  :  10.3390/en7117535

来源: mdpi

【 摘 要 】

In order to obtain a deeper understanding of the regenerative cooling process of scramjet engines, in this paper, a numerical investigation on the supercritical convective heat transfer of n-decane in horizontal circular tubes was conducted, based on a complete set of conservation equations and the Renormalization group (RNG) k–ε turbulence model with enhanced wall treatment. The present study mainly focuses on the heat transfer deterioration (HTD) phenomenon, including the mechanism and critical conditions for the onset of HTD. Moreover, the applicability of some conventional heat transfer empirical correlations was analyzed and compared, thus providing guidance for the Nusselt number predictions in the cooling channels. Results indicate that under the compositive conditions of low pressure and high heat flux, two types of HTD phenomena could occur when the wall and bulk fluid temperatures are near the pseudo-critical temperature, owing to the abnormal distributions of near-wall turbulent kinetic energy and radial velocity, respectively. Increasing the pressure would effectively alleviate and eliminate the HTD. A comparison of numerical results with those obtained with different empirical expressions shows that the Bae-Kim expression provides the best agreement, especially when HTD occurs. Furthermore, a new correction for critical heat flux of HTD has been successfully developed.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.