A one-dimensional modelling methodology of printed circuit heat exchangers for steady, off-design and transient feasibility in a supercritical CO 2 power block

As the most widely-used heaters and recuperators in supercritical CO 2 ( sCO 2 ) power cycles, the Printed Circuit Heat Exchangers (PCHEs) have received considerable interest to investigate their steady, off-design and transient behaviour mainly by simulations, which remains a challenging task accounting for various application scenarios. After an introduction and comparison about the state-of-art PCHEs numerical approaches, this paper presents a generic one-dimensional (1D) numerical PCHE modelling methodology featured by (1) ability fulfilling the steady, off-design and transient simulation; (2) precise capture of the non-linear local variations in the thermo-physical properties of sCO 2 ; (3) feasibility for a wide range of flow patterns, working fluids, and operation conditions. The off-design prediction via the proposed 1D PCHE modelling methodology is justified by validating its Modelica implementation against previous literature. Later, one optimal Nusselt correlation out of five candidates is identified to reproduce two typical transient power cycle operations, i.e., 'shutdown and startup' and 'ramp-up' scenario. These scenarios are validated by experiments at the Pinjarra Hills High Pressure Loop (PHPL) of the University of Queensland. The proposed 1D PCHE model successfully follows the changing rules of the time-varying temperature of both hot- and cold-side working fluids, though a slight time lag is observed between the simulation and experiment, which is caused by the modelling assumptions. In general, the presented 1D PCHE modelling methodology is credited for the steady, part-load and transient performance evaluation of sCO 2 power blocks and the corresponding control strategy development. Several crucial future work is summarized for guidance.