Parametric Optimization of a W-Type Shell and Tube Helium–HITEC Molten Salt Heat Exchanger for DEMO

The planned DEMOnstration fusion power plant is designed to operate in a pulse (BURN-DWELL) regime, using a balance of plant with an intermediate heat transfer system which, in some cases, utilizes helium and molten salt as heat transfer medium. For that gas–molten salt heat exchangers are one of the crucial components. Therefore, a W-type shell and tube heat exchanger with helium inside the tubes and molten HITEC salt outside the tubes is proposed. In order to optimize the heat exchanger design, an in-house numerical code and an evaluation function were developed. Searching the parameters space of more than 11 000 combinations (sets) with varying tube inner diameter, tube wall thickness, pitch, and number of tube heat exchangers with minimal values of the optimization coefficient were identified. The optimal heat exchanger design found has 35 000 tubes of 10 mm inner diameter, 12 mm outer diameter, and 21 mm pitch, and the equivalent size of the heat exchanger is ⊘7.9 × 29.6 m with 0.3-MPa pressure loss in the primary heat transfer system helium and 3.6 MPa pressure loss in the intermediate heat transfer system molten HITEC salt, while transferring 262.8 MW of heat from helium to the HITEC molten salt.