循环射流混合槽内湍流强化传热数值模拟及射流层优化

循环射流混合槽(CJT)作为一种过程强化设备可以提高湍流的混合效率及反应选择性。为进一步提高其工业应用价值，对循环射流混合槽流场的传热能力进行分析并对其射流层数进行结构优化。在恒壁温的条件下，采用SST k-ω模型分析循环射流混合槽流场区域的非稳态流动传热特性。在充分湍流状态下研究了Re=3260~16 303，射流层数M=5~9对循环射流混合槽壁面对流传热特性及流场传热特性的影响。结果表明，M=9时对流换热系数的变异系数Ch随Re增加而减少，壁面传热均匀性提高2.8%~19.3%；流场与温度场协同性随Re增加而增加，Re=16 303时的协同角为75.5o比Re=3260时减小约0.5°。Re=9782时Ch随M增加而降低，壁面传热均匀性提高2.7%~16.3%；速度矢量与温度梯度协同性随M增加而减小，M=9时全局协同性相较于M=5时降低了6.1%。当M=7时中心混合区与射流混合区的场协同角均在73°~74°之间，两区域流场间热量传递能力匹配程度较好；当M<7时中心混合区的协同性优于射流混合区，当M>7时射流混合区协同性优于中心混合区。研究Re及射流层数M对循环射流混合槽热量吸收和传递性能的影响，发现Re的变化对循环射流混合槽吸热量的影响大于射流层数M的变化。

Numerical simulation of turbulence heat transfer enhancement and optimization of jet layer in circulating jet mixing tank

Circulating jet mixing tank (CJT) as a process intensification can improve the turbulent mixing and reaction selectivity of flowing working medium. In order to further improve its industrial application value, the heat transfer capacity of the flow field inside the CJT was analyzed and the number of jet layers was optimized. Under the condition of constant wall temperature, the SST k-ω model was used to analyze the flow heat transfer performance of the flow field in the non-steady state calculation. The heat transfer uniformity of the wall and the heat transfer characteristics in the flow field was studied at Re= 3260~16 303 and the number of jet layers M=5~9. The variation coefficient Ch of convective heat transfer coefficient decreased and the uniformity of wall heat transfer increased by 2.8%~19.3% with the increasing Re for M=9. The field-synergy between flow field and temperature field increased with the increase of Re and the synergy angle at Re=16 303 is 75.5o, which is 0.5° less than that at Re=3260. The Ch decreased and the heat transfer uniformity increased by 2.7%~16.3% with the increasing M for Re=9782. The field-synergy between velocity vector and temperature gradient decreased with the increasing M. Compared with synergy at M=5, the global synergy decreased by 6.1% at M=9. When M=7, the field-synergy angles in the central mixing region and the jet mixing region were between 73° and 74°, and the heat transfer capacity between the two regions was well matched. The synergy of central mixing region was better than that of jet mixing region for M<7, and the situation was opposite when M>7. The influence of Re and M on the heat absorption and transfer performance of the CJT was studied. It was found that the change of Re had more influence on the heat absorption of the CJT with respect to M.