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在大大小小的化学工厂中,我们常会碰到不少的传热设备,其中如蒸发器,冷凝器,再馏器(reboiler),加热器,冷却器等等,都是常用到的.在过去、已经有很多化工工作者在这方面花过不少精力,奠定了各种物质的物理性质,流动情况与传热率的关系,并把这些关系,具体应用到换热设备的设计及及操作上来,图积法和对数平均法是二个具有代表性的例子,由于换热设备的改良,多程(multipass)管(壳殳)式换热器的出现,对数平均法后来又有了不少的补充与修正.不过因为自然对流及辐射率的关系复杂,一般情况下的散热不多,所以寻常换热设备的设计,通常都是按绝热的假定得来,再不然,就把安全因素加大些,或者假定某些变数的变化很少,凭经验加些保热材料,至于结合漏热率于设计的工作做的极少.
In large and small chemical plants, we often encounter a lot of heat transfer equipment, including the evaporator, condenser, reboiler (reboiler), heaters, coolers, etc., are commonly used in In the past, many chemical workers had spent a lot of energy in this respect, laying down the relationship between the physical properties of various substances and the heat transfer rate. They also applied these relations specifically to the design of heat exchange equipment and / Operation, graph plot method and logarithmic average method are two representative examples. Due to the improvement of heat exchange equipment and the emergence of multipass (shell) heat exchangers, the logarithmic average method There are a lot of additions and amendments.But because of the natural convection and the relationship between the emissivity is complex, under normal circumstances less heat, so the design of ordinary heat exchange equipment, usually based on the assumption of adiabatic, or not To increase the safety factor, or assume that some changes in the few variables, experience plus some thermal materials, as the combination of heat leak rate in the design work done very little.