遇到一个匪夷所思的HTRI问题? 蒸汽和水 换热器 ,蒸汽侧 流量40.2t/h,250度 1.0MPa,水侧流量968t/h,进出口温度为75/100度,压力700Kpa。 换热器的DUTY空着,让程序自己算。 上述数据定死 现在的变化污垢热阻, 污垢=0.00035的时候,Overdesign=0%,U require= 1280.43 污垢=0.00025的时候,Overdesign=20%,U require= 1280.56 污垢=0.00000的时候,Overdesign=131%,U require= 1282.15 奇怪,U require为什么会微幅变动?难道是 predicted mean temperature difference也就是EMTD有了微幅变动? Actual U Overall heat transfer coefficient based on predicted film coefficients using specified fouling resistances Unless the percent overdesign is zero, this value is not the one you calculate using U = Q / (Effective Area * EMTD). Required U Overall coefficient required to achieve specified exchanger duty with actual surface area and predicted mean temperature difference This value can be calculated as U = Q / (Effective Area * EMTD) Overdesign If negative, amount of underdesign This value is based on specified duty if input, on calculated duty if duty not input. Overdesign is calculated as follows: % Overdesign = 100(Uo /Ureq –1)查看更多3个回答 . 3人已关注