Based on mechanism analysis of rotary air heaters,taking the metal element as a hypothesis fluid,which exchange heat directly with flue gas (primary and secondary air) in a micro-control volume,heat-transfer differential equations and corresponding difference equations were established for the heaters.According to the thermal design and structure parameters of a 600 MW subcritical unit,a model was set up and solved,so as to obtain the reasonable temperature distribution in the metallic heat-retaining element and working medium,and to obtain the variation law of exhaust gas temperature and outlet air temperature by changing the air leakage coefficient.Results show that the increase of air leakage rate will lead to the rise of exhaust gas heat loss,which brings negative influence on the boiler efficiency;the exhaust gas temperature of air heater shows an increasing tendency,while the primary/secondary air temperature shows a downtrend,with an increasing proportion of air leakage at hot end.%通过对回转式空气预热器进行机理分析,将旋转运动的蓄热元件作为金属流体,与烟气(一、二次风)在微元控制体中进行直接换热,建立了传热微分方程及差分方程,根据某600 MW亚临界机组的空气预热器的结构参数及设计参数,通过模型求解得到空气预热器蓄热元件壁温及工质温度分布,并改变漏风分配系数,得到排烟温度及空气出口温度的变化规律.结果表明:漏风率增大会导致排烟损失增大,锅炉效率下降;随着热端漏风占比增大,空气预热器排烟温度呈上升趋势,一、二次风出口温度呈下降趋势.
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