Giant and robust thermal nonreciprocity in a fluid-solid multiphase circulator

Nonreciprocal heat transfer is crucial for modern energy utilization and conversion. Rotational bias in circulators made of fluid or solid monophase materials enables thermal nonreciprocity at two output ports. However, sensitivity to multiple factors like port position and circulator radius necessitates precise rotational bias, making giant thermal nonreciprocity fragile. Here, we propose a fluid-solid multiphase circulator by incorporating a solid rotating ring into a fluid circulator. The rotation speed flexibly controls the heat exchange ratio between the fluid-solid interface. Giant thermal nonreciprocity is obtained when the solid and fluid speeds are nearly synchronized, yielding distinctly different temperature amplitudes at two output ports. The rectification ratio robustly reaches the maximum due to its independence of port position and circulator radius. These findings also apply to more ports and other diffusion domains like mass transport, inspiring a fluid-solid hybrid paradigm for diffusion regulation.