产生污垢后,总传热系数为=dfrac (1)(dfrac {d)({d)_(1)(d)_(1)}+(R)_(5)dfrac ({d)_(1)}({d)_(1)}+dfrac (b{d)_(0)}(lambda {d)_(m)}+(R)_(30)+dfrac (1)({d)_(0)}-|||-= __-|||-1-|||-0.004295+0.00025×-|||-=209.23W/((m)^2cdot (C)_(2))热阻增加的百分数为=dfrac (1)(dfrac {d)({d)_(1)(d)_(1)}+(R)_(5)dfrac ({d)_(1)}({d)_(1)}+dfrac (b{d)_(0)}(lambda {d)_(m)}+(R)_(30)+dfrac (1)({d)_(0)}-|||-= __-|||-1-|||-0.004295+0.00025×-|||-=209.23W/((m)^2cdot (C)_(2))例-4 在一套管换热器中,用冷却水将热流体由 90℃冷却至65℃,冷却水进口温度为 25℃,出口温度为60℃,试分别计算两流体作逆流和并流时的平均温度差。

产生污垢后,总传热系数为

热阻增加的百分数为

例-4 在一套管换热器中,用冷却水将热流体由 90℃冷却至65℃,冷却水进口温度为 25℃,出口温度为60℃,试分别计算两流体作逆流和并流时的平均温度差。

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