How to refine the internal grid of the indoor airflow field

The surface grid has already been refined, but the internal grid is still coarse.This is a screenshot of the grid in ParaView:

Translation: I have tried many methods to refine the grid, but only the surface grid is refined while the interior grid remains large, resulting in rough simulation results.
Is there any other method to refine the interior grid? I also tried setting a refinement region, but I encountered an error message saying “1. Solution exception: ‘Case’ object has no attribute ‘add_refinement_region’”.

You can use boundingbox compotent to generate a box for whole room. Then use refine region for indoor room grid refine.