换热器设计裕量与旁路设计分析

The analysis of the overdesign and the bypass design for the heat exchanger

在换热器的冷端或者热端增设旁路,可以增加控制的自由度,有利于操作平稳。当换热器增设旁路时,换热器设计裕量的大小对于旁路控制的有效性十分重要。目前,做工艺设计时,通常根据设计经验而确定设计裕量的大小,使得换热器的面积裕量过大或设计裕量不足,难以满足控制的要求。本文提出了一种定量求解换热器设计裕量的方法,对比分析旁路设计时操作裕量、结垢裕量和控制裕量的大小,为旁路优化控制奠定基础。最后结合实例证明定量求解设计裕量是十分必要的,且设置旁路可以使换热器在保证操作平稳的同时总满足控制要求。对换热器设计裕量与旁路设计的分析为提高换热网络的控制效果,节能降耗奠定了基础。

Through placing the bypass on the cold side or/and hot side of the heat exchanger, the degree of freedom of control can be promoted, and the stability of operation can be improved. Once the bypass is placed, the overdesign becomes very important for the effectiveness of the control. The designer always decides the amount of overdesign based on the designing experience and the variation of the operation, so that the heat exchanger area may not meet the requirement of control. The method of solving the amount of overdesign is presented, the comparison of the operation, fouling and control overdesign was also analyzed, which is the basis of bypass optimal control. Combined with the example, the results showed the calculation of overdesign is necessary, and the control requirement can be satisfied, at the same time the stability of operation can be proved by the bypass. The analysis of the overdesign and bypass design is the basis of the control of the heat exchangers network.