In this research, taking into account the pressure drop of the streams, a simple and useful method is presented for finding the proper path of hot and cold streams inside shell-tube heat exchangers in the synthesis of heat exchangers networks (HENs). Generally, the HENs synthesis by mathematical programming leads to the problems which are answered by Mixed Integer Non Linear Programming (MINLP) methods. Optimization of such formulations results convergence difficulties due to the existence of both continuous and integer variables. In this study, instead of solving simultaneously integer and continuous variables, the genetic algorithm was used to find optimal HEN structure (integer variables). To find optimal values for continuous variables of the network, by categorizing this type of variables into two groups and using Quasi Linear Programming (QLP) instead of the nonlinear programming model (NLP), the complexity of the NLP model solution is also greatly reduced. The optimal values of continuous and integer variables are obtained with respect to a common objective function that reaches the minimum annual cost of the HEN. The comparison of the proposed method with the references shows that this method has the ability to reduce the cost of pumping flows to about 0.76%.