酸性离子交换树脂催化4-芳基-1H-1,2,3-三唑的合成

Numerical Investigation of the Flow and Heat Transfer of n-Decane in Helical-Coiled Tubes at Supercritical Pressure

使用高比热容的航空燃料对航空发动机的冷却空气进行预冷却是改善航空发动机冷却性能的有效方法。采用数值模拟方法研究了超临界压力下正癸烷在不同导程参数的螺旋管内速度场和温度场分布特性,结果表明：螺旋管离心力引起的二次流是使截面速度出现差异的主要原因,流体速度的最大值位于外侧壁面处;流体温度较高的区域靠近螺旋管内侧壁面处且随着螺旋上升角度的增大而逐渐扩大;模拟所得的努塞尔数和压降与Petukhov等的经验公式吻合较好,说明该公式同样适用正癸烷在螺旋管内的流动传热计算;螺旋管导程对管内流体的流动和传热性能影响很小,在螺旋管换热器优化设计中应作为次要优化参数。

It is an effective method to improve the cooling performance of aero-engine by using high thermal capacity aviation fuel to cool the cooling air.Numerical simulation of the helical-coiled tubes with different helical pitch was carried out to analyze the distributions of both velocity and temperature fields.The results show that the secondary flow caused by the centrifugal force of the helical-coil tubes is the main reason for the difference in the distribution of both velocity and temperature.The maximum velocity is found at the outer side while the high temperature zone is found at the inner side.Moreover,the area of the high temperature zone expands gradually with the increase of the helix angel.The simulation results of Nusselt number and pressure drop accord well with those of the empirical formulas presented by Petukhov et al,which shows that these formulas are also applicable to the calculation of the flow and heat transfer of n-decane in the helical-coiled tube.The helical pitch has little influence on the flow performance and heat transfer in helical-coiled tubes,and it should be considered as a secondary factor in optimal design of helical-coiled tubes heat exchanger.