Thermo-economic optimization and design of the heat exchangers in the feedwater line of the power conversion system coupled to DEMO fusion reactor

• A novel thermo-economic optimization of shell and tube heat exchangers is presented. • This methodology has been applied to design the heat exchangers in DEMO power cycle. • An iterative thermal simulation model of the heat exchangers has been implemented. • The economic calculation is based on Purohit method for shell and tube exchangers. This article presents a methodology for the thermo-economic optimization of shell-and-tube heat exchangers and its direct application to the design of the heat exchangers in the Feedwater Line of DEMO Power Conversion System, for the Helium-Cooled Pebble Bed Balance of Plant concept. This optimization consists of minimizing the heat exchanger total present cost comprising both the investment cost and the operating cost related to the pumping power to overcome friction losses while ensuring an efficient heat transfer performance. For the calculation of the investment cost, a detailed and particularized method for Shell-and-Tube heat exchangers is proposed, which provides very accurate values as related to the actual cost of these heat exchangers. For the pumping power calculation, both tube-side and shell-side fluids pressure drops are included. This calculation is performed by an iterative process, which results finally in the determination of all the thermal parameters that characterize the heat exchanger. The final selection of the heat exchanger also includes specific constructive and design constraints of these heat exchangers, which will also be described in this work.