大粗糙度横肋管摩擦阻力与传热特性

在凝结换热实验台上 ,采用恒壁温法和恒热流法对油品在大粗糙度横肋管中的层流与湍流摩擦阻力与传热特性进行了实验研究 .实验过程中Re为 5 0～ 6 2 0 0 ,Pr为 75～ 2 6 0 ,管子粗糙高度为 5mm ,导程为 30mm .实验结果表明 ,由于实验管特殊几何结构 (大粗糙度 )和油品物性参数的相互作用 ,使其表现出与以水或空气为工质的常用强化管不同的流动传热规律 ,并且实验方法对实验结果的影响不大 .根据实验结果 ,提出了层流区和湍流区油品量纲 1摩擦系数及传热系数的关联式 ,并将实验数据与Ravigururajan和Bergles关联式的计算值进行了比较 .研究结果可用于大粗糙度横肋管换热器的设计及运行参数优化 .

FRICTION AND HEAT TRANSFER CHARACTERISTICS OF TRANSVERSE TUBE WITH LARGE ROUGHNESS

Investigations were carried out, under uniform wall temperature and constant heat flux boundary conditions,on heat transfer and frictional characteristics of transverse tube with large roughness for laminar and turbulent flow of oil in a condensation test facility.The parameters tested were Re =50-6200, Pr =75-260,roughness height e =5mm,and pitch p =30mm.The experimental results show that the frictional and heat transfer characteristics of test tube differed greatly with those of conventional enhanced tubes,which use water or air as working fluid,due to the interaction of its special geometrical configurations and oil thermal properties.Also,the difference in friction and heat transfer data by using different test methods was found to be extremely small.The correlations of dimensionless friction factors and heat transfer coefficients were proposed on the basis of experimental data.Finally the experimental data were compared with computational results obtained by Ravigururajan and Bergles correlation.