帘式折流片换热器强化传热数值研究

Numerical Research on Heat Transfer Enhancement of Shutter Baffle Heat Exchanger

为解决折流板换热器壳程流体阻力过大和折流杆换热器低Re下传热系数较小等管壳式换热器的不足,提出了壳程流体"斜向流"的新概念,研制了新型高效节能管壳式换热器?帘式折流片换热器,其壳程传热系数高于折流杆换热器20%～30%,而壳程压力损失大幅低于折流板换热器。以场协同原理分析了斜向流的强化传热机理,指出在帘式折流片换热器壳程中流体速度场与温度梯度场间的夹角小于折流杆换热器,是其强化传热的重要原因。对帘式折流片换热器中折流栅间距、折流片倾角、折流片宽度等重要几何参数对传热和压降的影响规律进行了数值模拟研究,并据此推导了壳程传热系数和流体阻力降准数关联式,为其工程设计和推广应用提供了参考依据。

In order to overcome some disadvantages of shell-and-tube heat exchanger, such as the too high pressure drop in shell side of segmental baffle heat exchanger, and the low heat transfer coefficient in rod baffle heat exchanger with the low Re condition in shell side, a new concept of ＂Sideling Flow＂ in shell side of shell-and-tube heat exchanger was presented, and a new style energy saving shell-and-tube heat exchanger, shutter baffle heat exchanger, was developed. The heat transfer coefficient in shell side of shutter baffle heat exchanger is 20%～30% higher than that of rod baffle heat exchanger, and the pressure drop in shell side is much lower than that of segmental baffle heat exchanger. The Field Synergy Principle was adopted to analyze the heat transfer enhancement mechanism of sideling flow, it indicates that the synergy angle between the flow velocity field and temperature grads field around the tubes in shutter baffle heat exchanger is smaller than that in rod baffle heat exchanger, which is the main cause of heat transfer enhancement in shutter baffle heat exchanger. Effects of some important structural parameters, such as the distance between two adjacent shutter baffles, inclination angle of strips, width of strips and so on, on the fluid flow and heat transfer performance of shutter baffle heat exchanger were also investigated by numerical simulation. According to the simulation above, both the correlative equations of the heat transfer coefficient and pressure drop in shell side were given, which provides the references for the design and popularization of the shutter baffle heat exchanger.