Non-equilibrium overlapping grid method with two-phase porous media model for printed circuit heat exchanger based steam generator

The printed circuit heat exchanger (PCHE) is a promising alternative for the once-through steam generator (OTSG) of small modular reactors due to its compact structure and high efficiency. To study the effect of flow maldistribution on the performance of heat transfer and thermal stress, it is necessary to conduct three-dimensional full-scale simulation of two-side fluid and solid domains in the printed circuit heat exchanger based steam genarator (PCHESG). However, there is a lack of mature thermal-hydraulic models for the PCHESG. This work proposes a non-equilibrium overlapping grid method with two-phase porous media model for the PCHESG. The temperature and flow fields of the PCHESG under high-pressure conditions are evaluated. Compared to traditional methods, the new method greatly reduces the order of magnitude of the grid number from 10⁷∼10⁹ to 10⁶ and the computational time from days to hours. It is found that the flow maldistribution with a threshold cold-side mass flow rate of 0.08∼0.0944 kg/s induced by the header parts of the PCHESG deteriorates the total heat transfer rate by 58.8 % and increases the spatial non-uniformity of the temperature and phase distributions. The solid domain is solved simultaneously and its temperature non-uniformity becomes significant with a threshold cold-side mass flow rate of 0.04∼0.06 kg/s. The results demonstrate that this method has great potential in achieving rapid design and optimization for the PCHESG.