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一、前言目前我国一些中小容量的锅炉及加热炉的排烟温度多在250～400℃左右,大量余热未获利用,这不仅造成能量的浪费,而且在工业集中的地区还会造成环境的热污染。降低排烟温度常用的方法是增设省煤器及空气预热器,利用烟气余热提高锅炉给水温度及进入炉内助燃空气的温度。空气预热器通常是一种间壁式气—气换热器,但由于其传热系数K及空气与烟气之间的平均温差Δtm都很小,为达到一定的传热量势必要有相当大的传热面积F。F的增大,意味着换热设备的庞大,并带来以下三个方面的不利;(1) 由于金属耗量大,增加了设备投资;(2) 占地面积大,增加
I. Preface At present, the discharge temperature of some medium and small capacity boilers and furnaces in our country is mostly around 250-400 ℃, a large amount of waste heat is not utilized, which not only results in the waste of energy but also causes the environmental heat in the industrial concentrated areas Pollution. Commonly used methods to reduce the exhaust gas temperature are adding economizers and air preheaters, using the waste heat of the flue gas to raise the boiler feed water temperature and the temperature of the combustion air entering the furnace. Air preheaters are usually wall-to-wall heat exchangers, but due to their heat transfer coefficient K and the average temperature difference Δtm between the air and the flue gas are small, there is a need to have a considerable amount of heat transfer Of the heat transfer area F. The increase of F means that the heat exchange equipment is huge and brings the following three disadvantages: (1) the equipment investment is increased due to the large metal consumption, (2) the large area and the increase