孔板结构换热器传热与阻力性能的数值模拟

基于周期性全截面模型及RNG k-ε湍流模型，运用计算流体力学软件FLUENT对不同孔板结构换热器壳程流体流动以及传热性能进行了数值模拟分析，并通过文献试验数据验证了该数值模拟方法的可行性和准确性。在此基础上，对比分析了三叶孔、四叶孔、五叶孔、大圆孔、小圆孔等5种孔板结构的传热与阻力性能，探讨了支撑板等结构参数对其传热与阻力性能的影响，进一步采用场协同原理探讨了孔板换热器的强化传热机理。研究结果表明：采用RNG k-ε湍流模型以及周期性全截面模型可较为准确地模拟孔板换热器壳程流体流动情况；5种模型中五叶孔换热器的传热特性最好但阻力最大，小圆孔的传热效果最差但阻力最小；随着支撑板间距以及开孔高度的增加，换热器壳程的传热系数和压力降均逐渐降低；在支撑板后，速度矢量与温度梯度之间的夹角波动幅度变化剧烈，起到了强化壳程传热的效果；其中五叶孔板的场协同角波动幅度最大，强化传热效果最好。

Numerical study on heat transfer and resistance performance of heat exchangers with perforated-baffle structure

Based on simplified periodic model and RNG k-ε turbulence model, the flow characteristics and heat transfer properties of shell-side fluid in perforated-baffle heat exchangers were numerically simulated by using CFD software FLUENT. The feasibility and accuracy of numerical simulation method was verified by experiment. The heat transfer and resistance performance of trefoil-baffle, four-leaf-hole baffle, five-leaf-hole baffle, big-hole baffle and small-hole baffle are analyzed. Then the influences of structural parameters on heat transfer and resistance performance were discussed. Furthermore, heat transfer enhancement mechanism of perforated-baffle structure heat exchangers was investigated based on the field synergy principle. The results showed that the fluid flow in the shell-side of the perforated-baffle structure heat exchanger can be accurately simulated by using the RNG k-ε turbulence model and the simplified periodic model. The heat transfer coefficient of five-leaf-hole baffle is the best while the resistance the greatest. The heat transfer coefficient of the small-hole baffle is the worst, while the resistance is the least. The heat transfer coefficient and pressure drop decrease when baffle pitch and hole-height increase. Behind the support plate, the angle between the velocity vector and the temperature gradient varies violently, which enhances the heat transfer in the shell-side. The field synergy angle of five-leaf-hole baffle has the largest fluctuation range, and the enhancement of heat transfer effect is the best.