Synthesis of heat exchanger networks including expansion process is a complex task due to the involvement of both heat and work. A stream that expands through expanders can produce work and cold load

while expansion through valves barely affects heat integration. In addition

expansion through expanders at higher temperature produces more work

but consumes more hot utility. Therefore

there is a need to weigh work production and heat consumption. To this end

an enhanced stage-wise superstructure is proposed that involves synchronous optimization of expander/valve placement and heat integration for each pressure-change sub-stream in stages. A mixed-integer nonlinear programming (MINLP) model is established for synthesizing sub and aboveambient heat exchanger networks with multi-stream expansion

which explicitly considers the optimized selection of end-heaters and end-coolers to adjust temperature requirement. Our proposed method can commendably achieve the optimal selection of expanders and valves in a bid for minimizing exergy consumption and total annual cost. Four example studies are conducted with two distinct objective function (minimization of exergy consumption and total annual cost

respectively) to illustrate the feasibility and efficacy of the proposed method.