Promising designs of compact heat exchangers for modular HTRs using the Brayton cycle

The presented study was carried out within the Work Package 2 “Recuperator” of the High Temperature Reactor-E European program. High Temperature gas cooled Reactor concepts with a direct cycle have become potentially interesting for the future. Theoretically, these concepts provide higher efficiency than a classical steam cycle. Within the Brayton cycle the helium/helium recuperator, required to achieve the high efficiency, has to work under very harsh conditions (temperature, pressure, and pressure difference between circuits). Within the project the most promising technologies for the compact recuperator were investigated. First, the requirements for the recuperator to operate under the direct Brayton cycle have been defined. Based on these requirements the various potential technologies available on the market have been investigated. Two particular technologies (HEATRIC Printed Circuit Heat Exchanger, NORDON plate fin concept) have been selected as most promising. For the former, a precise description has been given and a mock-up has been fabricated and tested in the Claire loop at CEA. In the Claire loop the Printed Circuit Heat Exchanger mock-up has been subjected to thermal shocks, which are considered to be representative for a recuperator. Prior to the experimental testing coupled Computational Fluid Dynamic (CFD) and Finite Element analyses have been performed to give insight into the thermal and mechanical behaviour of the mock-ups during the thermal shock. Based on these results the experimental measuring program has been optimized. Upon completion of the tests the experimental and numerical results have been compared. Based on the results from the investigation performed recommendations are given for the full-size recuperator using the selected technologies.