非能动余热排出换热器冷凝换热性能研究

以浸没在高位水箱中的竖直管束为研究对象,对不同热负荷条件下竖直管束内冷凝换热特性进行研究,通过对比中心管与周围旁管的凝液增长率以及冷凝换热热阻,分析了中心管与旁管换热特性的差异,解释了低压条件下冷凝换热系数剧烈下降现象。将管束冷凝试验数据与已有单管试验数据对比发现,在相同蒸汽工况下,单管的冷凝换热系数与旁管的冷凝换热系数吻合较好,但远低于中心管的冷凝换热系数,说明中心管的换热性能相对于旁管确实得到了强化。通过对比换热系数的试验值与经典努塞尔理论和努塞尔修正理论的计算值发现,中心管的试验值与努塞尔修正理论计算值吻合较好,但旁管的偏差较大。

Research on Characteristics of Condensation Heat Transfer for Passive Residual Heat Removal Heat Exchanger

This experiment is to investigate the condensation heat transfer characteristic of vertical tube bundle by controlling the steam parameters in vertical tubes immersed in head water tank. To explain the phenomenon of a sharp decline of condensation heat transfer coefficient and the difference of condensation heat transfer characteristics between center tube and side tube, the growth rate of condensate and condensation thermal resistance were analyzed detailedly. The experimental results show that the condensation heat transfer coefficient of tube bundle is significant better than that of single tube, especially the condensation heat transfer coefficient of the center tube is much better than that of side tube under the same steam conditions. Through the contrast of heat transfer coefficient of the test value and the calculated values of both the classical and the modified Nusselt theories, the results show that the test value of center tube accords well with the calculation value of the modified Nusselt theory, but the deviation of side tube is larger.