新型铸铁板翅空气预热器翅片设计等效热流模型

Equivalent Heat Flowing Model for Fin Design of New Cast Iron Plate-fin Air Pre-heater

为了完善换热翅片板优化设计技术体系,从换热翅片几何尺寸优化的角度构建了一个新的判断标准,即等效热流结构原理。首先根据间壁式换热流通过程中各单元等面积和等容积的原理,建立了双侧单翅片换热流程的结构模型并构建了数学模型。其次建立了六面体形的翅片基本结构模型,该模型可以转化适用于其他常见翅片结构。把翅片容积与翅片面积的比值定义为翅片的容面比,作为判断翅片尺寸优化的综合性性量化指标。研究结果表明,翅片板的基板厚度应与单个翅片的容面比相当,薄基板的传热效果更好。同样的翅片尺寸,传热效果随基板的厚度增加而降低;换热流程上模型各流通单元的容面比应大小相当或有序排列;单翅片的容面比随着翅片高度或翅片宽度的增大而增大,不再随翅片尺寸的增大而增大的容面比是优化翅片的容面比;翅片的设计可以先优化尺寸,再优化结构;空气预热器烟气侧流程的整体容面比低于空气侧流程的整体容面比,会有利于使翅片板温度更接近于烟气侧温度,规避结露的可能。

In order to improve technology system for optimized design of heat exchanging plate fin, a new jud- ging criteria that equivalent heat flowing principle is established from the view of optimized geometry size of heat ex- changing fin. Firstly, based on the theory of individual unit area and volume equivalence during heat flowing process of dividing wall type heat exchange, both the structure model and its mathematic model of single fin on double sides are set up. Moreover, a basic structure model of hex-shape fin is set up as well. This model can be transformed and applied to other ordinary fin structures. The volume area rate can be defined as the proportion of one fin＇s volume to the fin＇s surface area and can be used to be the synthetized performance index to judge the opti- mum of the fin size. The research results show that thickness of the basic plate is equal to one fin＇s volume area rate, the heat exchanging effect of thin plate is better than that of the thick plate, and this heat exchanging effect is decreased as the thickness of basic plate for the same fin increased. All the volume area rate of each heat exchan- ging unit in heat flow line is equal or distributed in order. Individual fin＇s volume area rate is increasing as the en- larging thickness of height and width of the fin. The volume area rate is the optimized volume area rate when it is no longer increasing as fin＇ size enlarges. Size optimizing shall be considered firstly, and then optimizing of structure during fin designing. Because the integral volume area rate of flue gas side is lower than that of the air flow side in air pre-heater, it is better for the temperature of fin plate getting closer to the temperature of flue gas side so as to avoid dew condensing.