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采用标准k-ε湍流模型、基于有限体积法,对Ra数1.12×106-1.02×108,Pr数101-127范围内竖排等温管束对原油的自然对流换热特性进行了数值研究。结果表明,随相邻加热管中心距增加,管束整体依次经历了换热恶化、强化、稳定和衰退的不同阶段。底部加热管自然对流诱发的流体流动增大了上层管周围流体的速度,对上层管换热具有强化作用,但同时也改变了上层管周围流体的温度分布,导致上层管换热恶化和Nu数随时间产生波动。此外,存在换热强化和最高换热强度的临界中心距都随Ra数增大而减小,换热强化作用随Pr数增大而减弱,增加上层管数在一定程度上可提高管束的平均换热强度。
The standard k-ε turbulence model was used to study the natural convection heat transfer characteristics of crude oil with the vertical isothermal tube bundle with Ra number of 1.12 × 106-1.02 × 108 and Pr number of 101-127 based on the finite volume method. The results show that with the increase of the center distance of the adjacent heating tubes, the whole tube bundle successively undergoes different stages of deterioration, enhancement, stabilization and decline of heat transfer. The flow convection induced by natural convection of the bottom heating tube increases the velocity of the fluid around the upper tube and enhances the heat transfer of the upper tube but also changes the temperature distribution of the fluid around the upper tube and leads to the deterioration of the heat transfer and Nu number of the upper tube Volatile over time. In addition, the critical center distance with heat transfer enhancement and maximum heat transfer intensity decreases with increasing Ra number, and the heat transfer enhancement decreases with increasing Pr number. Increasing the upper tube number can improve the average tube bundle Heat exchange intensity.