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本文通过数值方法对三种热边界下管内SCO_2的换热特点进行了研究,结果表明,不同于常物性流体,SOO_2在三种不同的热边界下局部换热性能有明显差异。研究发现,第一类热边界(恒定壁温)下流体的温升明显快于第二类(恒定热流密度)和第三种热边界条件(与H_2O耦合换热),而第二类和第三种热边界条件虽然壁面热流分布有差异,但SCO_2的温升过程及沿程的换热系数分布具有一定相似性。以SCO_2为工质,在对管壳式换热器管侧进行简化时,与定壁温边界相比,采用定壁热流边界与实际的双流体耦合换热工况更加接近。
In this paper, the heat transfer characteristics of SCO_2 under three kinds of thermal boundaries are studied numerically. The results show that there are significant differences in the local heat transfer performance of SOO_2 under three different thermal boundaries, unlike the conventional fluids. It is found that the temperature rise of the fluid under the first type of thermal boundary (constant wall temperature) is obviously faster than that of the second type (constant heat flux) and the third thermal boundary condition (coupled with H_2O), while the second and Although the distribution of wall heat flux is different among the three kinds of thermal boundary conditions, the temperature rise process of SCO_2 and the heat transfer coefficient distribution along the process have some similarities. Taking SCO_2 as the working fluid, when the shell side of the shell-and-tube heat exchanger is simplified, compared with the fixed wall temperature boundary, the boundary between the fixed wall heat flow and the actual two-fluid coupling heat transfer is closer.