交错蛇形短翅片对扁平管外传热的强化

在火电机组直接空冷凝汽器中采用空冷技术,可以有效降低富煤缺水地区火力发电对水资源的消耗。通过数值模拟的方法,对锯齿形短翅片应用于火电机组直接空冷凝汽器扁平管空气侧强化传热的可行性进行探讨。研究发现,,采用所提出的扁平管交错蛇形短翅片结构,与传统的连续蛇形翅片相比,在各种迎面风速条件下均能起到强化空气侧传热的效果。随着短翅片交错排数的增加,翅片变短,强化传热的效果更为明显。在n 5时,强化传热综合性能评价准则数(performance evaluation criteria,PEC)可达到1.05~1.09;但随着迎面风速的增加,流动阻力的增加变得更为显著,强化传热的效果受到抑制。利用实际数据对模型的有效性进行验证,并对计算域网格数进行校验,结果表明所得结论具有一定的可靠性。

Heat Transfer Enhancement of Staggered Short Wavy Fins on Flat Tube

In direct air-cooled condenser(ACC) of power generating unit,the ambient air replaces the water as cooling medium.Air-cooled condensers with obvious water conservation benefit can be an important alternative for power plant near coal mines where water source is of shortage.The feasibility of air-side heat transfer enhancement by staggered short wavy fins to flat tube in air-cooled condenser of power generating unit was studied by numerical simulations.The results show that the heat transfer can be enhanced under various air flow velocities by staggered short fins compared with that by the traditional wave finned on flat tube.Heat transfer enhancement becomes remarkable while the staggered number of short fins increases.The performance evaluation criteria(PEC) can be as high as 1.05~1.09 under the condition that the staggered number of short fins is 5.On the other hand,the PEC decreases under the high air side flow velocities,indicating that the heat transfer enhancement can be restrained by the pressure drop loss.The present results can be verified by the turbulent models and grid number verifications.