A controllable bypass optimal design method is presented.The way to establish a heat exchanger networks(HEN)model was derived for the quantitative analysis of relative gain array(RGA).From the point of view of controllability

a HEN non-square RGA(ns-RGA)was calculated iteratively

and then the optimal bypass location was determined to ensure a more controllable HEN.Generically

RGA was used to select appropriate manipulated variables for target temperatures

but it was a breakthrough here and a novel optimal bypass location method was presented by iteratively calculating the HEN ns-RGA.Some guidelines were given to simplify the work.A case analysis indicated that changes of normal operation state of the HEN would not impact the bypasses location

which was derived from the above method.This method was adaptable to complex HEN

and could guarantee a more controllable HEN for production.A case study demonstrated the effectiveness and feasibility of the method proposed in this paper.