微细管内超临界CO_(2)传热恶化机理研究  

Study on heat transfer deterioration mechanism of supercritical CO_(2) in miniature tubes

作　　者：苏成杰 陈昊楠 姜文全[2] Su Chengjie;Chen Haonan;Jiang Wenquan(China Coal Science and Technology Group Shenyang Research Institute Co.Ltd,State Key Laboratory of Coal Mine Safety Technology,Fushun 113122,China;School of Mechanical Engineering,Liaoning Petrochemical University,Fushun 113001,China)

机构地区：[1]中煤科工集团沈阳研究院有限公司煤矿安全技术国家重点实验室,抚顺113122 [2]辽宁石油化工大学机械工程学院,抚顺113001

出　　处：《低温与超导》2024年第5期81-87,94,共8页Cryogenics and Superconductivity

基　　金：辽宁省教育厅高校基本科研项目(LJKMZ20220725)资助。

摘　　要：本文采用FLUENT软件和自编程序调用REFPROP软件中物性参数,选取k-kl-ω湍流模型,模拟了热流密度、质量流量及管径等因素对超临界CO_(2)的传热过程的影响。结果表明:在7.5 MPa超临界压力下,常规细管(D=2 mm)内,随热流密度的增加,超临界CO_(2)的传热系数降低,传热恶化现象愈加明显;然而,随着质量流量的增加,超临界CO_(2)的传热系数亦随之增加,传热恶化随之减弱;缩小管径能够提高传热系数,减小管径能够起到抑制传热恶化的作用。在高热流密度或低质量流量下,顶母线处“类气膜”厚度明显增加,抑制热量向主流区传递;同时在2 mm管径下,流速矢量图中涡心向管壁靠近,二次流未得到充分发展,进一步表明浮升力效应是传热恶化的主要原因,同时通过浮生力的影响分析,提出了微细管内超临界CO_(2)传热恶化新的毕渥数阈值Bo=3.5×10-5。The effects of heat flow density,mass flow rate and tube diameter on the supercritical CO_(2)heat transfer process were simulated by using FLUENT sofware and a self-programmed program to invoke the physical property parameters in REFPROP sofware,and the k-kl-turbulence model was selected.The results show that under 7.5 MPa supercritical pressure,in conventional thin tubes(D=2 mm),with the increase of heat flow density,the heat transfer coefficient of supercritical CO_(2) decreases,and heat transfer deterioration becomes more obvious;however,with the increase of mass flow rate,the heat transfer coefficient of supercritical CO,increases,and heat transfer deterioration becomes weaker.Reducing the pipe diameter can improve the heat transfer coefficient,and reducing the pipe diameter can inhibit the deterioration of heat transfer.Under high heat flux or low mass flow rate,the thickness of the"gas-like film"at the top bus increases significantly,which inhibits the heat transfer to the main flow area;meanwhile,the vortex centre is close to the wall of the tube in the flow velocity vector diagram under the tube diameter of 2 mm,and the secondary flow is not developed sufficiently,which further suggests that the effect of the floating force is the main reason for the deterioration of heat transfer;finally,through the analysis of the influence of the buoyancy force,a new Biot number threshold Bo=3.5×10^(-5) for the deterioration of supercritical CO,heat transfer in microfine tubes is proposed.

关 键 词：超临界压力CO_(2) 微细管 浮升力 类气膜 传热恶化 

分 类 号：TK124[动力工程及工程热物理—工程热物理]