摘要
针对超临界CO_2流体特殊的热物性所导致的奇异流动传热规律,开展了2mm内径的水平光滑圆管的传热试验研究。试验压力为7.4~8MPa,质量流速为600~1 000kg/(m^2·s),最大热流密度为94.2kW/m^2。试验获得了壁温和传热系数的变化规律,分析了不同的试验工况下无量纲浮升力和热加速的变化规律。结果表明:流体的传热系数峰值随热流密度升高逐渐向入口移动;不同无量纲浮升力的变化趋势存在较大的偏差,Kim的浮升力公式可较好地评判浮升力的大小;热加速效应在低热流密度下不显著,在高热流密度下呈现先递增后递减的趋势;当浮升力因子小于5.6×10^(-7)和热加速因子小于0.000 5时,浮升力效应和热加速效应可忽略。将浮升力和热加速因子引入新的Nusselt预测关联式,其平均误差为-2.92%,均方根误差为10.96%。
According to the complex thermophysical properties of supercritical CO 2,the heat transfer experiments on a smooth horizontal tube with a 2 mm inner diameter were carried out.The test pressure was 7.4-8 MPa,the mass flux was about 600-1 000 kg/(m 2·s),and the maximum heat flux was 94.2 kW/m 2.Through experiments,the wall temperature and local heat transfer coefficient were obtained.The non-dimensional buoyancy and thermal acceleration behavior under different experimental conditions were analyzed.The results show that the peak heat transfer coefficient of the fluid increases gradually with the heat flux and that there exists great deviation in the variation trend for different non-dimensional buoyancy.The Kim’s buoyancy correlation can better judge the value of buoyancy.Three different non-dimensional thermal accelerations indicate that the effect of thermal acceleration at low heat flux is not significant,while at high heat flux the acceleration effect presents a first increasing then decreasing tendency.When the buoyancy factor and thermal acceleration factor are less than 5.6×10-7 and 0.000 5,respectively,the effects of both buoyancy and thermal acceleration can be ignored.By taking into account both buoyancy and thermal acceleration,a new Nusselt correlation can be established.The average error and root mean square error of the correlation is-2.92%and 10.96%,respectively.
作者
吕海财
赵金乐
潘辉
刘朝晖
毕勤成
Lv Haicai;ZHAO Jinle;PAN Hui;LIU Zhaohui;BI Qincheng(State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)
出处
《西安交通大学学报》
EI
CAS
CSCD
北大核心
2018年第9期140-147,共8页
Journal of Xi'an Jiaotong University
基金
国家自然科学基金资助项目(51776167)
关键词
超临界CO2
传热
水平管
浮升力
热加速
supercritical CO 2
heat transfer
horizontal tube
buoyancy
thermal acceleration
