水在水平管束管外池沸腾传热的实验研究

Pool Boiling Heat Transfer of Water in a Horizontal Tube Bundle

通过对水在水平管束管外池沸腾的实验研究，探讨了沸腾换热系数随热流密度及沿管排高度变化的规律和内在机理．由实验结果发现：管束中各排测量管的沸腾换热系数明显高于单管池沸腾的情况；管束沸腾时存在管束效应，即随管排位置增高，起始沸腾点提前，沸腾曲线上移，沸腾换热系数增大；这种管束效应在部分核态沸腾时较强，而在充分发展核态沸腾时较弱；管束池沸腾的强化传热应归因于“滑移汽泡”及“诱发自然循环对流”机制．此外，还得出了管束池沸腾换热系数的经验关系式．

Pool boiling heat transfer of water is investigated for a horizontal tube bundle. Heat transfer characteristics are examined for each row of tube under a series of heat fluxes. The results show that heat transfer coefficients in the tube bundle are higher than that for a single tube. And for tubes with a higher elevation in the bundle there prevails a lower incipient heat flux, an upper boiling curve and a higher heat transfer coefficient. Furthermore, the 'bundle effect' (heat transfer augmentation in a tube bundle) is strong in partial nucleate boiling, but weak in fully developed nucleate boiling. It can be concluded that the main mechanism for pool boiling heat transfer augmentation in a tube bundle is the existence of sliding bubbles and the induced natural circulation of the boiling liquid. In addition, a correlation between boiling heat transfer coefficients and heat fluxes was developed.